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<div class="body" role="main"><div class="section" id="module-sqlite3"><h1><span class="yiyi-st" id="yiyi-10">12.6. <a class="reference internal" href="#module-sqlite3" title="sqlite3: A DB-API 2.0 implementation using SQLite 3.x."><code class="xref py py-mod docutils literal"><span class="pre">sqlite3</span></code></a> - SQLite数据库的DB-API 2.0接口</span></h1><p><span class="yiyi-st" id="yiyi-11"><strong>源代码：</strong> <a class="reference external" href="https://hg.python.org/cpython/file/3.5/Lib/sqlite3/">Lib / sqlite3 /</a></span></p><p><span class="yiyi-st" id="yiyi-12">SQLite 是一个C库，它提供了一个轻量级的基于磁盘的数据库，它不需要一个单独的服务器进程，并允许使用非标准的SQL查询语言的变体访问数据库。</span><span class="yiyi-st" id="yiyi-13">一些应用程序可以使用SQLite来存储内部数据。</span><span class="yiyi-st" id="yiyi-14">也可以使用SQLite来建立应用原型，随后再将代码移植到大型的数据库，比如PostgreSQL或者Oracle。</span></p><p><span class="yiyi-st" id="yiyi-15">sqlite3模块由Gerhard Häring编写。</span><span class="yiyi-st" id="yiyi-16">它提供了一个SQL接口，该接口和<a class="pep reference external" href="https://www.python.org/dev/peps/pep-0249"><strong>PEP 249</strong></a>描述的<span class="target" id="index-0">DB-API 2.0规范</span>兼容。</span></p><p><span class="yiyi-st" id="yiyi-17">若要使用该模块，必须首先创建一个表示数据库的<a class="reference internal" href="#sqlite3.Connection" title="sqlite3.Connection"><code class="xref py py-class docutils literal"><span class="pre">Connection</span></code></a>对象。</span><span class="yiyi-st" id="yiyi-18">这里的数据将存储在<code class="file docutils literal"><span class="pre">example.db</span></code>文件：</span></p><pre><code class="language-python"><span></span><span class="kn">import</span> <span class="nn">sqlite3</span>
<span class="n">conn</span> <span class="o">=</span> <span class="n">sqlite3</span><span class="o">.</span><span class="n">connect</span><span class="p">(</span><span class="s1">'example.db'</span><span class="p">)</span>
</code></pre><p><span class="yiyi-st" id="yiyi-19">也可以使用特殊名称<code class="docutils literal"><span class="pre">:memory:</span></code>以在 RAM（内存）中创建数据库。</span></p><p><span class="yiyi-st" id="yiyi-20">一旦有了一个<a class="reference internal" href="#sqlite3.Connection" title="sqlite3.Connection"><code class="xref py py-class docutils literal"><span class="pre">Connection</span></code></a>，就可以创建<a class="reference internal" href="#sqlite3.Cursor" title="sqlite3.Cursor"><code class="xref py py-class docutils literal"><span class="pre">Cursor</span></code></a>对象并调用其<a class="reference internal" href="#sqlite3.Cursor.execute" title="sqlite3.Cursor.execute"><code class="xref py py-meth docutils literal"><span class="pre">execute()</span></code></a>方法来执行 SQL 命令：</span></p><pre><code class="language-python"><span></span><span class="n">c</span> <span class="o">=</span> <span class="n">conn</span><span class="o">.</span><span class="n">cursor</span><span class="p">()</span>
<span class="c1"># Create table</span>
<span class="n">c</span><span class="o">.</span><span class="n">execute</span><span class="p">(</span><span class="s1">'''CREATE TABLE stocks</span>
<span class="s1"> (date text, trans text, symbol text, qty real, price real)'''</span><span class="p">)</span>
<span class="c1"># Insert a row of data</span>
<span class="n">c</span><span class="o">.</span><span class="n">execute</span><span class="p">(</span><span class="s2">"INSERT INTO stocks VALUES ('2006-01-05','BUY','RHAT',100,35.14)"</span><span class="p">)</span>
<span class="c1"># Save (commit) the changes</span>
<span class="n">conn</span><span class="o">.</span><span class="n">commit</span><span class="p">()</span>
<span class="c1"># We can also close the connection if we are done with it.</span>
<span class="c1"># Just be sure any changes have been committed or they will be lost.</span>
<span class="n">conn</span><span class="o">.</span><span class="n">close</span><span class="p">()</span>
</code></pre><p><span class="yiyi-st" id="yiyi-21">保存过的数据是持久的并在以后的会话中可用：</span></p><pre><code class="language-python"><span></span><span class="kn">import</span> <span class="nn">sqlite3</span>
<span class="n">conn</span> <span class="o">=</span> <span class="n">sqlite3</span><span class="o">.</span><span class="n">connect</span><span class="p">(</span><span class="s1">'example.db'</span><span class="p">)</span>
<span class="n">c</span> <span class="o">=</span> <span class="n">conn</span><span class="o">.</span><span class="n">cursor</span><span class="p">()</span>
</code></pre><p><span class="yiyi-st" id="yiyi-22">通常的SQL操作需要使用Python变量中的值。</span><span class="yiyi-st" id="yiyi-23">你不应该使用Python的字符串操作来组合查询，因为这样做是不安全的；它使你的程序容易受到SQL注入攻击（参见<a class="reference external" href="https://xkcd.com/327/">https://xkcd.com/327/</a>，这是关于可能出错的幽默例子）。</span></p><p><span class="yiyi-st" id="yiyi-24">相反，应该使用 DB API 参数替代。</span><span class="yiyi-st" id="yiyi-25">放置<code class="docutils literal"><span class="pre">?</span></code></span><span class="yiyi-st" id="yiyi-26">作为占位符，只要您想要使用值，然后提供一个元组值作为光标的<a class="reference internal" href="#sqlite3.Cursor.execute" title="sqlite3.Cursor.execute"><code class="xref py py-meth docutils literal"><span class="pre">execute()</span></code></a>方法的第二个参数。</span><span class="yiyi-st" id="yiyi-27">（其他的数据库模块可能使用不同的占位符，如<code class="docutils literal"><span class="pre">%s</span></code>或<code class="docutils literal"><span class="pre">:1</span></code>。)</span><span class="yiyi-st" id="yiyi-28">举个例子：</span></p><pre><code class="language-python"><span></span><span class="c1"># Never do this -- insecure!</span>
<span class="n">symbol</span> <span class="o">=</span> <span class="s1">'RHAT'</span>
<span class="n">c</span><span class="o">.</span><span class="n">execute</span><span class="p">(</span><span class="s2">"SELECT * FROM stocks WHERE symbol = '</span><span class="si">%s</span><span class="s2">'"</span> <span class="o">%</span> <span class="n">symbol</span><span class="p">)</span>
<span class="c1"># Do this instead</span>
<span class="n">t</span> <span class="o">=</span> <span class="p">(</span><span class="s1">'RHAT'</span><span class="p">,)</span>
<span class="n">c</span><span class="o">.</span><span class="n">execute</span><span class="p">(</span><span class="s1">'SELECT * FROM stocks WHERE symbol=?'</span><span class="p">,</span> <span class="n">t</span><span class="p">)</span>
<span class="nb">print</span><span class="p">(</span><span class="n">c</span><span class="o">.</span><span class="n">fetchone</span><span class="p">())</span>
<span class="c1"># Larger example that inserts many records at a time</span>
<span class="n">purchases</span> <span class="o">=</span> <span class="p">[(</span><span class="s1">'2006-03-28'</span><span class="p">,</span> <span class="s1">'BUY'</span><span class="p">,</span> <span class="s1">'IBM'</span><span class="p">,</span> <span class="mi">1000</span><span class="p">,</span> <span class="mf">45.00</span><span class="p">),</span>
<span class="p">(</span><span class="s1">'2006-04-05'</span><span class="p">,</span> <span class="s1">'BUY'</span><span class="p">,</span> <span class="s1">'MSFT'</span><span class="p">,</span> <span class="mi">1000</span><span class="p">,</span> <span class="mf">72.00</span><span class="p">),</span>
<span class="p">(</span><span class="s1">'2006-04-06'</span><span class="p">,</span> <span class="s1">'SELL'</span><span class="p">,</span> <span class="s1">'IBM'</span><span class="p">,</span> <span class="mi">500</span><span class="p">,</span> <span class="mf">53.00</span><span class="p">),</span>
<span class="p">]</span>
<span class="n">c</span><span class="o">.</span><span class="n">executemany</span><span class="p">(</span><span class="s1">'INSERT INTO stocks VALUES (?,?,?,?,?)'</span><span class="p">,</span> <span class="n">purchases</span><span class="p">)</span>
</code></pre><p><span class="yiyi-st" id="yiyi-29">为了取回<a class="reference internal" href="../glossary.html#term-iterator"><span class="xref std std-term">iterator</span></a>语句的执行结果，你可以把游标cursor 当做是一个迭代器，通过调用游标的<a class="reference internal" href="#sqlite3.Cursor.fetchone" title="sqlite3.Cursor.fetchone"><code class="xref py py-meth docutils literal"><span class="pre">fetchone()</span></code></a>方法来获取单行结果；或者通过调用<a class="reference internal" href="#sqlite3.Cursor.fetchall" title="sqlite3.Cursor.fetchall"><code class="xref py py-meth docutils literal"><span class="pre">fetchall()</span></code></a>方法获取结果集列表。</span></p><p><span class="yiyi-st" id="yiyi-30">此示例使用迭代器形式：</span></p><pre><code class="language-python"><span></span><span class="gp">&gt;&gt;&gt; </span><span class="k">for</span> <span class="n">row</span> <span class="ow">in</span> <span class="n">c</span><span class="o">.</span><span class="n">execute</span><span class="p">(</span><span class="s1">'SELECT * FROM stocks ORDER BY price'</span><span class="p">):</span>
<span class="go"> print(row)</span>
<span class="go">('2006-01-05', 'BUY', 'RHAT', 100, 35.14)</span>
<span class="go">('2006-03-28', 'BUY', 'IBM', 1000, 45.0)</span>
<span class="go">('2006-04-06', 'SELL', 'IBM', 500, 53.0)</span>
<span class="go">('2006-04-05', 'BUY', 'MSFT', 1000, 72.0)</span>
</code></pre><div class="admonition seealso"><p class="first admonition-title"><span class="yiyi-st" id="yiyi-31">请参见</span></p><dl class="last docutils"><dt><span class="yiyi-st" id="yiyi-32"><a class="reference external" href="https://github.com/ghaering/pysqlite">https://github.com/ghaering/pysqlite</a></span></dt><dd><span class="yiyi-st" id="yiyi-33">pysqlite网页 - sqlite3是在名称“pysqlite”外部开发的。</span></dd><dt><span class="yiyi-st" id="yiyi-34"><a class="reference external" href="https://www.sqlite.org">https://www.sqlite.org</a></span></dt><dd><span class="yiyi-st" id="yiyi-35">SQLite网页；该文档描述了支持的SQL方言的语法和可用的数据类型。</span></dd><dt><span class="yiyi-st" id="yiyi-36"><a class="reference external" href="http://www.w3schools.com/sql/">http://www.w3schools.com/sql/</a></span></dt><dd><span class="yiyi-st" id="yiyi-37">学习SQL语法的教程，参考和示例。</span></dd><dt><span class="yiyi-st" id="yiyi-38"><span class="target" id="index-1"></span> <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0249"><strong>PEP 249</strong></a> - 数据库API规范2.0</span></dt><dd><span class="yiyi-st" id="yiyi-39">PEP由Marc-AndréLemburg编写。</span></dd></dl></div><div class="section" id="module-functions-and-constants"><h2><span class="yiyi-st" id="yiyi-40">12.6.1. </span><span class="yiyi-st" id="yiyi-41">Module functions and constants</span></h2><dl class="data"><dt id="sqlite3.version"><span class="yiyi-st" id="yiyi-42"> <code class="descclassname">sqlite3.</code><code class="descname">version</code></span></dt><dd><p><span class="yiyi-st" id="yiyi-43">该模块的字符串形式的版本号。</span><span class="yiyi-st" id="yiyi-44">这不是 SQLite 库的版本。</span></p></dd></dl><dl class="data"><dt id="sqlite3.version_info"><span class="yiyi-st" id="yiyi-45"> <code class="descclassname">sqlite3.</code><code class="descname">version_info</code></span></dt><dd><p><span class="yiyi-st" id="yiyi-46">该模块的整数元组形式的版本号。</span><span class="yiyi-st" id="yiyi-47">这不是 SQLite 库的版本。</span></p></dd></dl><dl class="data"><dt id="sqlite3.sqlite_version"><span class="yiyi-st" id="yiyi-48"> <code class="descclassname">sqlite3.</code><code class="descname">sqlite_version</code></span></dt><dd><p><span class="yiyi-st" id="yiyi-49">运行期SQLite库的版本号，字符串形式。</span></p></dd></dl><dl class="data"><dt id="sqlite3.sqlite_version_info"><span class="yiyi-st" id="yiyi-50"> <code class="descclassname">sqlite3.</code><code class="descname">sqlite_version_info</code></span></dt><dd><p><span class="yiyi-st" id="yiyi-51">运行期SQLite库的版本号，整数元组形式。</span></p></dd></dl><dl class="data"><dt id="sqlite3.PARSE_DECLTYPES"><span class="yiyi-st" id="yiyi-52"> <code class="descclassname">sqlite3.</code><code class="descname">PARSE_DECLTYPES</code></span></dt><dd><p><span class="yiyi-st" id="yiyi-53">该常量用于<a class="reference internal" href="#sqlite3.connect" title="sqlite3.connect"><code class="xref py py-func docutils literal"><span class="pre">connect()</span></code></a>函数的<em>detect_types</em>参数。</span></p><p><span class="yiyi-st" id="yiyi-54">设置它使得<a class="reference internal" href="#module-sqlite3" title="sqlite3: A DB-API 2.0 implementation using SQLite 3.x."><code class="xref py py-mod docutils literal"><span class="pre">sqlite3</span></code></a>模块解析每个返回列的声明的类型。</span><span class="yiyi-st" id="yiyi-55">它将解析出声明的类型的第一个单词，比如，"integer primary key"，它将解析出"integer"，而"number(10)"，它将解析出"number"。</span><span class="yiyi-st" id="yiyi-56">然后对于那列，它将查询转换器字典并对类型使用对应注册的转换器函数。</span></p></dd></dl><dl class="data"><dt id="sqlite3.PARSE_COLNAMES"><span class="yiyi-st" id="yiyi-57"> <code class="descclassname">sqlite3.</code><code class="descname">PARSE_COLNAMES</code></span></dt><dd><p><span class="yiyi-st" id="yiyi-58">该常量用于<a class="reference internal" href="#sqlite3.connect" title="sqlite3.connect"><code class="xref py py-func docutils literal"><span class="pre">connect()</span></code></a>函数的<em>detect_types</em>参数。</span></p><p><span class="yiyi-st" id="yiyi-59">设置它使得SQLite接口解析每个返回列的列名。</span><span class="yiyi-st" id="yiyi-60">它将查找[mytype]形式的字符串，然后决定'mytype'是列的类型。</span><span class="yiyi-st" id="yiyi-61">将会尝试在转换器字典中找到对应于'mytype'的转换器，然后将转换器函数应用于返回的值。</span><span class="yiyi-st" id="yiyi-62"><a class="reference internal" href="#sqlite3.Cursor.description" title="sqlite3.Cursor.description"><code class="xref py py-attr docutils literal"><span class="pre">Cursor.description</span></code></a>中找到的的列名只是列名的第一个单词，即，如果SQL中有类似<code class="docutils literal"><span class="pre">'as</span> <span class="pre">"x</span> <span class="pre">[datetime]"'</span></code>的成分，那么第一个单词将会被解析成列名，直到有空格为止：列名只是简单的"x"。</span></p></dd></dl><dl class="function"><dt id="sqlite3.connect"><span class="yiyi-st" id="yiyi-63"> <code class="descclassname">sqlite3.</code><code class="descname">connect</code><span class="sig-paren">(</span><em>database</em><span class="optional">[</span>, <em>timeout</em>, <em>detect_types</em>, <em>isolation_level</em>, <em>check_same_thread</em>, <em>factory</em>, <em>cached_statements</em>, <em>uri</em><span class="optional">]</span><span class="sig-paren">)</span></span></dt><dd><p><span class="yiyi-st" id="yiyi-64">打开到SQLite数据库文件<em>database</em>的连接。</span><span class="yiyi-st" id="yiyi-65">可以使用<code class="docutils literal"><span class="pre">":memory:"</span></code>打开到内存的数据库的连接。</span></p><p><span class="yiyi-st" id="yiyi-66">当多个连接访问数据库，其中一个进程修改了数据库，SQLite数据库会锁定，直到事务被提交。</span><span class="yiyi-st" id="yiyi-67"><em>timeout</em>参数指明为了得到锁，连接最多等待多久，如果等待超时则抛出异常。</span><span class="yiyi-st" id="yiyi-68">超时参数的默认值是 5.0 （5 秒）。</span></p><p><span class="yiyi-st" id="yiyi-69">对于<em>isolation_level</em>参数，请参阅<a class="reference internal" href="#sqlite3.Connection.isolation_level" title="sqlite3.Connection.isolation_level"><code class="xref py py-attr docutils literal"><span class="pre">Connection.isolation_level</span></code></a>对象的<a class="reference internal" href="#sqlite3.Connection" title="sqlite3.Connection"><code class="xref py py-class docutils literal"><span class="pre">Connection</span></code></a>属性。</span></p><p><span class="yiyi-st" id="yiyi-70">SQLite 原生只支持文本、 整数、 实数，BLOB 和 NULL类型。</span><span class="yiyi-st" id="yiyi-71">如果您想要使用其他类型，必须自己添加对它们的支持。</span><span class="yiyi-st" id="yiyi-72"><em>detect_types</em>参数和使用由<a class="reference internal" href="#sqlite3.register_converter" title="sqlite3.register_converter"><code class="xref py py-func docutils literal"><span class="pre">register_converter()</span></code></a>函数注册的自定义<strong>转换器</strong>使得这很容易。</span></p><p><span class="yiyi-st" id="yiyi-73"><em>detect_types</em>默认为 0 （即关闭，没有类型检测），你可以将它设置为<a class="reference internal" href="#sqlite3.PARSE_DECLTYPES" title="sqlite3.PARSE_DECLTYPES"><code class="xref py py-const docutils literal"><span class="pre">PARSE_DECLTYPES</span></code></a>和<a class="reference internal" href="#sqlite3.PARSE_COLNAMES" title="sqlite3.PARSE_COLNAMES"><code class="xref py py-const docutils literal"><span class="pre">PARSE_COLNAMES</span></code></a>的任意组合以打开类型检测。</span></p><p><span class="yiyi-st" id="yiyi-74">默认情况下，<em>check_same_thread</em>是<a class="reference internal" href="constants.html#True" title="True"><code class="xref py py-const docutils literal"><span class="pre">True</span></code></a>，只有创建线程可以使用连接。</span><span class="yiyi-st" id="yiyi-75">如果设置为<a class="reference internal" href="constants.html#False" title="False"><code class="xref py py-const docutils literal"><span class="pre">False</span></code></a>，则返回的连接可以跨多个线程共享。</span><span class="yiyi-st" id="yiyi-76">当使用具有相同连接的多个线程时，写入操作应该由用户序列化以避免数据损坏。</span></p><p><span class="yiyi-st" id="yiyi-77">默认情况下， <a class="reference internal" href="#module-sqlite3" title="sqlite3: A DB-API 2.0 implementation using SQLite 3.x."><code class="xref py py-mod docutils literal"><span class="pre">sqlite3</span></code></a>模块使用<a class="reference internal" href="#sqlite3.Connection" title="sqlite3.Connection"><code class="xref py py-class docutils literal"><span class="pre">Connection</span></code></a>类以调用connect。</span><span class="yiyi-st" id="yiyi-78">然而，可以继承<a class="reference internal" href="#sqlite3.Connection" title="sqlite3.Connection"><code class="xref py py-class docutils literal"><span class="pre">Connection</span></code></a>类，通过将子类提供给<em>factory</em>参数，使得<a class="reference internal" href="#sqlite3.connect" title="sqlite3.connect"><code class="xref py py-func docutils literal"><span class="pre">connect()</span></code></a>使用你的子类。</span></p><p><span class="yiyi-st" id="yiyi-79">有关详细信息，请参阅该手册的<a class="reference internal" href="#sqlite3-types"><span>SQLite and Python types</span></a>的章节。</span></p><p><span class="yiyi-st" id="yiyi-80"><a class="reference internal" href="#module-sqlite3" title="sqlite3: A DB-API 2.0 implementation using SQLite 3.x."><code class="xref py py-mod docutils literal"><span class="pre">sqlite3</span></code></a>模块内部使用语句缓存来避免 SQL 解析开销。</span><span class="yiyi-st" id="yiyi-81">如果想要显式设置连接所缓存的语句的数量，可以设置<em>cached_statements</em>参数。</span><span class="yiyi-st" id="yiyi-82">在当前实现中的默认设置是缓存 100 条语句。</span></p><p><span class="yiyi-st" id="yiyi-83">如果<em>uri</em>为真，则<em>数据库</em>被解释为URI。</span><span class="yiyi-st" id="yiyi-84">这允许您指定选项。</span><span class="yiyi-st" id="yiyi-85">例如，要以只读模式打开数据库，您可以使用：</span></p><pre><code class="language-python"><span></span><span class="n">db</span> <span class="o">=</span> <span class="n">sqlite3</span><span class="o">.</span><span class="n">connect</span><span class="p">(</span><span class="s1">'file:path/to/database?mode=ro'</span><span class="p">,</span> <span class="n">uri</span><span class="o">=</span><span class="kc">True</span><span class="p">)</span>
</code></pre><p><span class="yiyi-st" id="yiyi-86">有关此功能的详细信息（包括已识别选项的列表），请参见<a class="reference external" href="https://www.sqlite.org/uri.html">SQLite URI文档</a>。</span></p><div class="versionchanged"><p><span class="yiyi-st" id="yiyi-87"><span class="versionmodified">在版本3.4中已更改：</span>添加了<em>uri</em>参数。</span></p></div></dd></dl><dl class="function"><dt id="sqlite3.register_converter"><span class="yiyi-st" id="yiyi-88"> <code class="descclassname">sqlite3.</code><code class="descname">register_converter</code><span class="sig-paren">(</span><em>typename</em>, <em>callable</em><span class="sig-paren">)</span></span></dt><dd><p><span class="yiyi-st" id="yiyi-89">注册可调用对象用来将来自数据库的bytestring转换成为自定义的Python类型。</span><span class="yiyi-st" id="yiyi-90">对数据库所有有<em>typename</em>类型的值调用该可调用对象。</span><span class="yiyi-st" id="yiyi-91">参见<a class="reference internal" href="#sqlite3.connect" title="sqlite3.connect"><code class="xref py py-func docutils literal"><span class="pre">connect()</span></code></a>函数的<em>detect_types</em>参数以了解类型检测是如何工作的。</span><span class="yiyi-st" id="yiyi-92">请注意<em>typename</em>的大小写和查询中类型的名称必须匹配 ！</span></p></dd></dl><dl class="function"><dt id="sqlite3.register_adapter"><span class="yiyi-st" id="yiyi-93"> <code class="descclassname">sqlite3.</code><code class="descname">register_adapter</code><span class="sig-paren">(</span><em>type</em>, <em>callable</em><span class="sig-paren">)</span></span></dt><dd><p><span class="yiyi-st" id="yiyi-94">注册可调用对象用来将自定义的 Python 类型<em>type</em>转换为 SQLite 的支持的类型。</span><span class="yiyi-st" id="yiyi-95">可调用<em>可调用</em>接受Python值作为单个参数，并且必须返回以下类型的值：int，float，str或bytes。</span></p></dd></dl><dl class="function"><dt id="sqlite3.complete_statement"><span class="yiyi-st" id="yiyi-96"> <code class="descclassname">sqlite3.</code><code class="descname">complete_statement</code><span class="sig-paren">(</span><em>sql</em><span class="sig-paren">)</span></span></dt><dd><p><span class="yiyi-st" id="yiyi-97">如果字符串<em>sql</em>包含一个或多个以分号结束的完整的SQL语句则返回<a class="reference internal" href="constants.html#True" title="True"><code class="xref py py-const docutils literal"><span class="pre">True</span></code></a>。</span><span class="yiyi-st" id="yiyi-98">它不验证SQL的语法正确性，只是检查没有未关闭的字符串常量以及语句是以分号结束的。</span></p><p><span class="yiyi-st" id="yiyi-99">这可以用于生成一个 sqlite shell，如以下示例所示：</span></p><pre><code class="language-python"><span></span><span class="c1"># A minimal SQLite shell for experiments</span>
<span class="kn">import</span> <span class="nn">sqlite3</span>
<span class="n">con</span> <span class="o">=</span> <span class="n">sqlite3</span><span class="o">.</span><span class="n">connect</span><span class="p">(</span><span class="s2">":memory:"</span><span class="p">)</span>
<span class="n">con</span><span class="o">.</span><span class="n">isolation_level</span> <span class="o">=</span> <span class="kc">None</span>
<span class="n">cur</span> <span class="o">=</span> <span class="n">con</span><span class="o">.</span><span class="n">cursor</span><span class="p">()</span>
<span class="n">buffer</span> <span class="o">=</span> <span class="s2">""</span>
<span class="nb">print</span><span class="p">(</span><span class="s2">"Enter your SQL commands to execute in sqlite3."</span><span class="p">)</span>
<span class="nb">print</span><span class="p">(</span><span class="s2">"Enter a blank line to exit."</span><span class="p">)</span>
<span class="k">while</span> <span class="kc">True</span><span class="p">:</span>
<span class="n">line</span> <span class="o">=</span> <span class="nb">input</span><span class="p">()</span>
<span class="k">if</span> <span class="n">line</span> <span class="o">==</span> <span class="s2">""</span><span class="p">:</span>
<span class="k">break</span>
<span class="n">buffer</span> <span class="o">+=</span> <span class="n">line</span>
<span class="k">if</span> <span class="n">sqlite3</span><span class="o">.</span><span class="n">complete_statement</span><span class="p">(</span><span class="n">buffer</span><span class="p">):</span>
<span class="k">try</span><span class="p">:</span>
<span class="n">buffer</span> <span class="o">=</span> <span class="n">buffer</span><span class="o">.</span><span class="n">strip</span><span class="p">()</span>
<span class="n">cur</span><span class="o">.</span><span class="n">execute</span><span class="p">(</span><span class="n">buffer</span><span class="p">)</span>
<span class="k">if</span> <span class="n">buffer</span><span class="o">.</span><span class="n">lstrip</span><span class="p">()</span><span class="o">.</span><span class="n">upper</span><span class="p">()</span><span class="o">.</span><span class="n">startswith</span><span class="p">(</span><span class="s2">"SELECT"</span><span class="p">):</span>
<span class="nb">print</span><span class="p">(</span><span class="n">cur</span><span class="o">.</span><span class="n">fetchall</span><span class="p">())</span>
<span class="k">except</span> <span class="n">sqlite3</span><span class="o">.</span><span class="n">Error</span> <span class="k">as</span> <span class="n">e</span><span class="p">:</span>
<span class="nb">print</span><span class="p">(</span><span class="s2">"An error occurred:"</span><span class="p">,</span> <span class="n">e</span><span class="o">.</span><span class="n">args</span><span class="p">[</span><span class="mi">0</span><span class="p">])</span>
<span class="n">buffer</span> <span class="o">=</span> <span class="s2">""</span>
<span class="n">con</span><span class="o">.</span><span class="n">close</span><span class="p">()</span>
</code></pre></dd></dl><dl class="function"><dt id="sqlite3.enable_callback_tracebacks"><span class="yiyi-st" id="yiyi-100"> <code class="descclassname">sqlite3.</code><code class="descname">enable_callback_tracebacks</code><span class="sig-paren">(</span><em>flag</em><span class="sig-paren">)</span></span></dt><dd><p><span class="yiyi-st" id="yiyi-101">默认情况下你不会在用户定义的函数、 聚合、 转换器、 授权者回调等地方得到回溯对象（调用栈对象）。</span><span class="yiyi-st" id="yiyi-102">如果想要调试它们，将<em>flag</em>设置为<code class="docutils literal"><span class="pre">True</span></code>调用此函数。</span><span class="yiyi-st" id="yiyi-103">之后可以在<code class="docutils literal"><span class="pre">sys.stderr</span></code>通过回调得到回溯。</span><span class="yiyi-st" id="yiyi-104">使用<a class="reference internal" href="constants.html#False" title="False"><code class="xref py py-const docutils literal"><span class="pre">False</span></code></a>来再次禁用该功能。</span></p></dd></dl></div><div class="section" id="connection-objects"><h2><span class="yiyi-st" id="yiyi-105">12.6.2. </span><span class="yiyi-st" id="yiyi-106">Connection Objects</span></h2><dl class="class"><dt id="sqlite3.Connection"><span class="yiyi-st" id="yiyi-107"> <em class="property">class </em><code class="descclassname">sqlite3.</code><code class="descname">Connection</code></span></dt><dd><p><span class="yiyi-st" id="yiyi-108">SQLite 数据库连接具有以下的属性和方法：</span></p><dl class="attribute"><dt id="sqlite3.Connection.isolation_level"><span class="yiyi-st" id="yiyi-109"> <code class="descname">isolation_level</code></span></dt><dd><p><span class="yiyi-st" id="yiyi-110">获取或设置当前隔离级别。</span><span class="yiyi-st" id="yiyi-111"><a class="reference internal" href="constants.html#None" title="None"><code class="xref py py-const docutils literal"><span class="pre">None</span></code></a>为自动提交模式；或者为"DEFERRED"、"IMMEDIATE"或"EXCLUSIVE"之一。</span><span class="yiyi-st" id="yiyi-112">参见<a class="reference internal" href="#sqlite3-controlling-transactions"><span>Controlling Transactions</span></a>章节以得到更详细的解释。</span></p></dd></dl><dl class="attribute"><dt id="sqlite3.Connection.in_transaction"><span class="yiyi-st" id="yiyi-113"> <code class="descname">in_transaction</code></span></dt><dd><p><span class="yiyi-st" id="yiyi-114"><a class="reference internal" href="constants.html#True" title="True"><code class="xref py py-const docutils literal"><span class="pre">True</span></code></a>如果交易处于活动状态（有未提交的更改），则<a class="reference internal" href="constants.html#False" title="False"><code class="xref py py-const docutils literal"><span class="pre">False</span></code></a>。</span><span class="yiyi-st" id="yiyi-115">只读属性。</span></p><div class="versionadded"><p><span class="yiyi-st" id="yiyi-116"><span class="versionmodified">版本3.2中的新功能。</span></span></p></div></dd></dl><dl class="method"><dt id="sqlite3.Connection.cursor"><span class="yiyi-st" id="yiyi-117"> <code class="descname">cursor</code><span class="sig-paren">(</span><span class="optional">[</span><em>cursorClass</em><span class="optional">]</span><span class="sig-paren">)</span></span></dt><dd><p><span class="yiyi-st" id="yiyi-118">游标方法接受单个可选参数<em>cursorClass</em>。</span><span class="yiyi-st" id="yiyi-119">如果提供，这必须是一个扩展<a class="reference internal" href="#sqlite3.Cursor" title="sqlite3.Cursor"><code class="xref py py-class docutils literal"><span class="pre">sqlite3.Cursor</span></code></a> 的自定义游标类。</span></p></dd></dl><dl class="method"><dt id="sqlite3.Connection.commit"><span class="yiyi-st" id="yiyi-120"> <code class="descname">commit</code><span class="sig-paren">(</span><span class="sig-paren">)</span></span></dt><dd><p><span class="yiyi-st" id="yiyi-121">此方法提交当前事务。</span><span class="yiyi-st" id="yiyi-122">如果不调用此方法，自上次调用<code class="docutils literal"><span class="pre">commit()</span></code>后做的任何改动对于其它数据库连接不可见。</span><span class="yiyi-st" id="yiyi-123">如果没有看到写入数据库的数据，请检查是否有调用该方法。</span></p></dd></dl><dl class="method"><dt id="sqlite3.Connection.rollback"><span class="yiyi-st" id="yiyi-124"> <code class="descname">rollback</code><span class="sig-paren">(</span><span class="sig-paren">)</span></span></dt><dd><p><span class="yiyi-st" id="yiyi-125">该方法回滚自从上一次<a class="reference internal" href="#sqlite3.Connection.commit" title="sqlite3.Connection.commit"><code class="xref py py-meth docutils literal"><span class="pre">commit()</span></code></a>调用之后对数据库所做的任何更改。</span></p></dd></dl><dl class="method"><dt id="sqlite3.Connection.close"><span class="yiyi-st" id="yiyi-126"> <code class="descname">close</code><span class="sig-paren">(</span><span class="sig-paren">)</span></span></dt><dd><p><span class="yiyi-st" id="yiyi-127">这将关闭数据库连接。</span><span class="yiyi-st" id="yiyi-128">请注意这不会自动调用<a class="reference internal" href="#sqlite3.Connection.commit" title="sqlite3.Connection.commit"><code class="xref py py-meth docutils literal"><span class="pre">commit()</span></code></a>。</span><span class="yiyi-st" id="yiyi-129">如果你关闭数据库连接没有先调用<a class="reference internal" href="#sqlite3.Connection.commit" title="sqlite3.Connection.commit"><code class="xref py py-meth docutils literal"><span class="pre">commit()</span></code></a> ，你的更改将会丢失 ！</span></p></dd></dl><dl class="method"><dt id="sqlite3.Connection.execute"><span class="yiyi-st" id="yiyi-130"> <code class="descname">execute</code><span class="sig-paren">(</span><em>sql</em><span class="optional">[</span>, <em>parameters</em><span class="optional">]</span><span class="sig-paren">)</span></span></dt><dd><p><span class="yiyi-st" id="yiyi-131">这是一个非正规的缩写，通过调用<a class="reference internal" href="#sqlite3.Connection.cursor" title="sqlite3.Connection.cursor"><code class="xref py py-meth docutils literal"><span class="pre">cursor()</span></code></a>方法创建一个游标对象，使用<em>参数</em>调用游标的<a class="reference internal" href="#sqlite3.Cursor.execute" title="sqlite3.Cursor.execute"><code class="xref py py-meth docutils literal"><span class="pre">execute()</span></code></a></span></p></dd></dl><dl class="method"><dt id="sqlite3.Connection.executemany"><span class="yiyi-st" id="yiyi-132"> <code class="descname">executemany</code><span class="sig-paren">(</span><em>sql</em><span class="optional">[</span>, <em>parameters</em><span class="optional">]</span><span class="sig-paren">)</span></span></dt><dd><p><span class="yiyi-st" id="yiyi-133">这是一个非标准快捷方式，通过调用<a class="reference internal" href="#sqlite3.Connection.cursor" title="sqlite3.Connection.cursor"><code class="xref py py-meth docutils literal"><span class="pre">cursor()</span></code></a>方法创建一个游标对象，使用给定的<em>参数</em>调用游标的<a class="reference internal" href="#sqlite3.Cursor.executemany" title="sqlite3.Cursor.executemany"><code class="xref py py-meth docutils literal"><span class="pre">executemany()</span></code></a></span></p></dd></dl><dl class="method"><dt id="sqlite3.Connection.executescript"><span class="yiyi-st" id="yiyi-134"> <code class="descname">executescript</code><span class="sig-paren">(</span><em>sql_script</em><span class="sig-paren">)</span></span></dt><dd><p><span class="yiyi-st" id="yiyi-135">这是一个非标准的快捷方式，通过调用<a class="reference internal" href="#sqlite3.Connection.cursor" title="sqlite3.Connection.cursor"><code class="xref py py-meth docutils literal"><span class="pre">cursor()</span></code></a>方法，使用给定的<em>sql_script</em>方法调用游标<a class="reference internal" href="#sqlite3.Cursor.executescript" title="sqlite3.Cursor.executescript"><code class="xref py py-meth docutils literal"><span class="pre">executescript()</span></code></a></span></p></dd></dl><dl class="method"><dt id="sqlite3.Connection.create_function"><span class="yiyi-st" id="yiyi-136"> <code class="descname">create_function</code><span class="sig-paren">(</span><em>name</em>, <em>num_params</em>, <em>func</em><span class="sig-paren">)</span></span></dt><dd><p><span class="yiyi-st" id="yiyi-137">创建一个自定义的函数，随后可以在SQL语句中以函数名<em>name</em>来调用它。</span><span class="yiyi-st" id="yiyi-138"><em>num_params</em>是函数接受的参数数量（如果<em>num_params</em>为-1，函数可以取任意数量的参数），<em>func</em>一个被称为SQL函数的Python可调用。</span></p><p><span class="yiyi-st" id="yiyi-139">函数可以返回SQLite支持的任何类型：bytes，str，int，float和None。</span></p><p><span class="yiyi-st" id="yiyi-140">示例：</span></p><pre><code class="language-python"><span></span><span class="kn">import</span> <span class="nn">sqlite3</span>
<span class="kn">import</span> <span class="nn">hashlib</span>
<span class="k">def</span> <span class="nf">md5sum</span><span class="p">(</span><span class="n">t</span><span class="p">):</span>
<span class="k">return</span> <span class="n">hashlib</span><span class="o">.</span><span class="n">md5</span><span class="p">(</span><span class="n">t</span><span class="p">)</span><span class="o">.</span><span class="n">hexdigest</span><span class="p">()</span>
<span class="n">con</span> <span class="o">=</span> <span class="n">sqlite3</span><span class="o">.</span><span class="n">connect</span><span class="p">(</span><span class="s2">":memory:"</span><span class="p">)</span>
<span class="n">con</span><span class="o">.</span><span class="n">create_function</span><span class="p">(</span><span class="s2">"md5"</span><span class="p">,</span> <span class="mi">1</span><span class="p">,</span> <span class="n">md5sum</span><span class="p">)</span>
<span class="n">cur</span> <span class="o">=</span> <span class="n">con</span><span class="o">.</span><span class="n">cursor</span><span class="p">()</span>
<span class="n">cur</span><span class="o">.</span><span class="n">execute</span><span class="p">(</span><span class="s2">"select md5(?)"</span><span class="p">,</span> <span class="p">(</span><span class="n">b</span><span class="s2">"foo"</span><span class="p">,))</span>
<span class="nb">print</span><span class="p">(</span><span class="n">cur</span><span class="o">.</span><span class="n">fetchone</span><span class="p">()[</span><span class="mi">0</span><span class="p">])</span>
</code></pre></dd></dl><dl class="method"><dt id="sqlite3.Connection.create_aggregate"><span class="yiyi-st" id="yiyi-141"> <code class="descname">create_aggregate</code><span class="sig-paren">(</span><em>name</em>, <em>num_params</em>, <em>aggregate_class</em><span class="sig-paren">)</span></span></dt><dd><p><span class="yiyi-st" id="yiyi-142">创建一个用户定义的聚合函数。</span></p><p><span class="yiyi-st" id="yiyi-143">聚合类必须实现<code class="docutils literal"><span class="pre">step</span></code>方法，该方法接受参数数量<em>num_params</em>（如果<em>num_params</em>为-1，的参数）和一个<code class="docutils literal"><span class="pre">finalize</span></code>方法，它将返回聚合的最终结果。</span></p><p><span class="yiyi-st" id="yiyi-144"><code class="docutils literal"><span class="pre">finalize</span></code>方法可以返回SQLite支持的任何类型：bytes，str，int，float和None。</span></p><p><span class="yiyi-st" id="yiyi-145">示例：</span></p><pre><code class="language-python"><span></span><span class="kn">import</span> <span class="nn">sqlite3</span>
<span class="k">class</span> <span class="nc">MySum</span><span class="p">:</span>
<span class="k">def</span> <span class="nf">__init__</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="bp">self</span><span class="o">.</span><span class="n">count</span> <span class="o">=</span> <span class="mi">0</span>
<span class="k">def</span> <span class="nf">step</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">value</span><span class="p">):</span>
<span class="bp">self</span><span class="o">.</span><span class="n">count</span> <span class="o">+=</span> <span class="n">value</span>
<span class="k">def</span> <span class="nf">finalize</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="k">return</span> <span class="bp">self</span><span class="o">.</span><span class="n">count</span>
<span class="n">con</span> <span class="o">=</span> <span class="n">sqlite3</span><span class="o">.</span><span class="n">connect</span><span class="p">(</span><span class="s2">":memory:"</span><span class="p">)</span>
<span class="n">con</span><span class="o">.</span><span class="n">create_aggregate</span><span class="p">(</span><span class="s2">"mysum"</span><span class="p">,</span> <span class="mi">1</span><span class="p">,</span> <span class="n">MySum</span><span class="p">)</span>
<span class="n">cur</span> <span class="o">=</span> <span class="n">con</span><span class="o">.</span><span class="n">cursor</span><span class="p">()</span>
<span class="n">cur</span><span class="o">.</span><span class="n">execute</span><span class="p">(</span><span class="s2">"create table test(i)"</span><span class="p">)</span>
<span class="n">cur</span><span class="o">.</span><span class="n">execute</span><span class="p">(</span><span class="s2">"insert into test(i) values (1)"</span><span class="p">)</span>
<span class="n">cur</span><span class="o">.</span><span class="n">execute</span><span class="p">(</span><span class="s2">"insert into test(i) values (2)"</span><span class="p">)</span>
<span class="n">cur</span><span class="o">.</span><span class="n">execute</span><span class="p">(</span><span class="s2">"select mysum(i) from test"</span><span class="p">)</span>
<span class="nb">print</span><span class="p">(</span><span class="n">cur</span><span class="o">.</span><span class="n">fetchone</span><span class="p">()[</span><span class="mi">0</span><span class="p">])</span>
</code></pre></dd></dl><dl class="method"><dt id="sqlite3.Connection.create_collation"><span class="yiyi-st" id="yiyi-146"> <code class="descname">create_collation</code><span class="sig-paren">(</span><em>name</em>, <em>callable</em><span class="sig-paren">)</span></span></dt><dd><p><span class="yiyi-st" id="yiyi-147">用指定的<em>name</em>和<em>callable</em>创建一个排序规则。</span><span class="yiyi-st" id="yiyi-148">将会传两个字符串参数给可调用对象。</span><span class="yiyi-st" id="yiyi-149">如果第一个比第二个小，返回-1；如果它们相等，返回0；如果第一个比第二个大，返回1。</span><span class="yiyi-st" id="yiyi-150">请注意它控制排序（SQL里的ORDER BY），所以不会影响其它的SQL操作。</span></p><p><span class="yiyi-st" id="yiyi-151">请注意可调用对象将会以Python bytestring的方式得到它的参数，一般为UTF-8编码。</span></p><p><span class="yiyi-st" id="yiyi-152">下面的示例演示自定义的排序规则以"错误方式"来排序：</span></p><pre><code class="language-python"><span></span><span class="kn">import</span> <span class="nn">sqlite3</span>
<span class="k">def</span> <span class="nf">collate_reverse</span><span class="p">(</span><span class="n">string1</span><span class="p">,</span> <span class="n">string2</span><span class="p">):</span>
<span class="k">if</span> <span class="n">string1</span> <span class="o">==</span> <span class="n">string2</span><span class="p">:</span>
<span class="k">return</span> <span class="mi">0</span>
<span class="k">elif</span> <span class="n">string1</span> <span class="o">&lt;</span> <span class="n">string2</span><span class="p">:</span>
<span class="k">return</span> <span class="mi">1</span>
<span class="k">else</span><span class="p">:</span>
<span class="k">return</span> <span class="o">-</span><span class="mi">1</span>
<span class="n">con</span> <span class="o">=</span> <span class="n">sqlite3</span><span class="o">.</span><span class="n">connect</span><span class="p">(</span><span class="s2">":memory:"</span><span class="p">)</span>
<span class="n">con</span><span class="o">.</span><span class="n">create_collation</span><span class="p">(</span><span class="s2">"reverse"</span><span class="p">,</span> <span class="n">collate_reverse</span><span class="p">)</span>
<span class="n">cur</span> <span class="o">=</span> <span class="n">con</span><span class="o">.</span><span class="n">cursor</span><span class="p">()</span>
<span class="n">cur</span><span class="o">.</span><span class="n">execute</span><span class="p">(</span><span class="s2">"create table test(x)"</span><span class="p">)</span>
<span class="n">cur</span><span class="o">.</span><span class="n">executemany</span><span class="p">(</span><span class="s2">"insert into test(x) values (?)"</span><span class="p">,</span> <span class="p">[(</span><span class="s2">"a"</span><span class="p">,),</span> <span class="p">(</span><span class="s2">"b"</span><span class="p">,)])</span>
<span class="n">cur</span><span class="o">.</span><span class="n">execute</span><span class="p">(</span><span class="s2">"select x from test order by x collate reverse"</span><span class="p">)</span>
<span class="k">for</span> <span class="n">row</span> <span class="ow">in</span> <span class="n">cur</span><span class="p">:</span>
<span class="nb">print</span><span class="p">(</span><span class="n">row</span><span class="p">)</span>
<span class="n">con</span><span class="o">.</span><span class="n">close</span><span class="p">()</span>
</code></pre><p><span class="yiyi-st" id="yiyi-153">若要删除一个排序规则，把None当作可调用对象来调用<code class="docutils literal"><span class="pre">create_collation</span></code>：</span></p><pre><code class="language-python"><span></span><span class="n">con</span><span class="o">.</span><span class="n">create_collation</span><span class="p">(</span><span class="s2">"reverse"</span><span class="p">,</span> <span class="kc">None</span><span class="p">)</span>
</code></pre></dd></dl><dl class="method"><dt id="sqlite3.Connection.interrupt"><span class="yiyi-st" id="yiyi-154"> <code class="descname">interrupt</code><span class="sig-paren">(</span><span class="sig-paren">)</span></span></dt><dd><p><span class="yiyi-st" id="yiyi-155">可以从另一个线程中调用该方法来中止该连接正在执行的查询。</span><span class="yiyi-st" id="yiyi-156">查询会中止，调用者会得到一个异常。</span></p></dd></dl><dl class="method"><dt id="sqlite3.Connection.set_authorizer"><span class="yiyi-st" id="yiyi-157"> <code class="descname">set_authorizer</code><span class="sig-paren">(</span><em>authorizer_callback</em><span class="sig-paren">)</span></span></dt><dd><p><span class="yiyi-st" id="yiyi-158">这个例程注册一个回调。</span><span class="yiyi-st" id="yiyi-159">每次尝试访问的数据库中的表的列，则调用该回调。</span><span class="yiyi-st" id="yiyi-160">如果访问被允许，回调应该返回<code class="xref py py-const docutils literal"><span class="pre">SQLITE_OK</span></code>；如果SQL语句应该以错误中止，回调应该返回<code class="xref py py-const docutils literal"><span class="pre">SQLITE_DENY</span></code>；如果列应该被当成NULL值，回调应该返回<code class="xref py py-const docutils literal"><span class="pre">SQLITE_IGNORE</span></code>。</span><span class="yiyi-st" id="yiyi-161">这些常量在<a class="reference internal" href="#module-sqlite3" title="sqlite3: A DB-API 2.0 implementation using SQLite 3.x."><code class="xref py py-mod docutils literal"><span class="pre">sqlite3</span></code></a>模块中可用</span></p><p><span class="yiyi-st" id="yiyi-162">回调的第一个参数表示何种操作被授权。</span><span class="yiyi-st" id="yiyi-163">根据第一个参数，第二和第三个参数将提供或是<a class="reference internal" href="constants.html#None" title="None"><code class="xref py py-const docutils literal"><span class="pre">None</span></code></a>。</span><span class="yiyi-st" id="yiyi-164">第四个参数是数据库的名称（“main”，“temp”等）</span><span class="yiyi-st" id="yiyi-165">如果适用。</span><span class="yiyi-st" id="yiyi-166">第5个参数是最内部的触发器或视图的名字，它们负责访问请求；如果访问请求直接来自于输入的SQL代码则为<a class="reference internal" href="constants.html#None" title="None"><code class="xref py py-const docutils literal"><span class="pre">None</span></code></a>。</span></p><p><span class="yiyi-st" id="yiyi-167">参阅SQlite的文档以了解第一个参数可能的值，以及第二个／第三个参数依赖于第一个参数的含义。</span><span class="yiyi-st" id="yiyi-168">所有必需的常量在<a class="reference internal" href="#module-sqlite3" title="sqlite3: A DB-API 2.0 implementation using SQLite 3.x."><code class="xref py py-mod docutils literal"><span class="pre">sqlite3</span></code></a>模块中可用。</span></p></dd></dl><dl class="method"><dt id="sqlite3.Connection.set_progress_handler"><span class="yiyi-st" id="yiyi-169"> <code class="descname">set_progress_handler</code><span class="sig-paren">(</span><em>handler</em>, <em>n</em><span class="sig-paren">)</span></span></dt><dd><p><span class="yiyi-st" id="yiyi-170">这个例程注册一个回调。</span><span class="yiyi-st" id="yiyi-171">SQLite虚拟机每执行<em>n</em>个指令调用该回调。</span><span class="yiyi-st" id="yiyi-172">如果希望在长时间操作过程中从SQLite得到调用，这是有用的，比如更新GUI。</span></p><p><span class="yiyi-st" id="yiyi-173">如果希望清除之前安装的过程处理器，以<a class="reference internal" href="constants.html#None" title="None"><code class="xref py py-const docutils literal"><span class="pre">None</span></code></a>为<em>handler</em>参数调用该方法。</span></p></dd></dl><dl class="method"><dt id="sqlite3.Connection.set_trace_callback"><span class="yiyi-st" id="yiyi-174"> <code class="descname">set_trace_callback</code><span class="sig-paren">(</span><em>trace_callback</em><span class="sig-paren">)</span></span></dt><dd><p><span class="yiyi-st" id="yiyi-175">要为SQLite后端实际执行的每个SQL语句调用寄存器<em>trace_callback</em>。</span></p><p><span class="yiyi-st" id="yiyi-176">传递给回调的唯一参数是正在执行的语句（作为字符串）。</span><span class="yiyi-st" id="yiyi-177">回调的返回值被忽略。</span><span class="yiyi-st" id="yiyi-178">请注意，后端不仅运行传递到<a class="reference internal" href="#sqlite3.Cursor.execute" title="sqlite3.Cursor.execute"><code class="xref py py-meth docutils literal"><span class="pre">Cursor.execute()</span></code></a>方法的语句。</span><span class="yiyi-st" id="yiyi-179">其他来源包括Python模块的事务管理和在当前数据库中定义的触发器的执行。</span></p><p><span class="yiyi-st" id="yiyi-180">将<a class="reference internal" href="constants.html#None" title="None"><code class="xref py py-const docutils literal"><span class="pre">None</span></code></a>作为<em>trace_callback</em>传递将禁用跟踪回调。</span></p><div class="versionadded"><p><span class="yiyi-st" id="yiyi-181"><span class="versionmodified">版本3.3中的新功能。</span></span></p></div></dd></dl><dl class="method"><dt id="sqlite3.Connection.enable_load_extension"><span class="yiyi-st" id="yiyi-182"> <code class="descname">enable_load_extension</code><span class="sig-paren">(</span><em>enabled</em><span class="sig-paren">)</span></span></dt><dd><p><span class="yiyi-st" id="yiyi-183">这个例程允许/不允许 SQLite 引擎从共享库加载 SQLite 扩展。</span><span class="yiyi-st" id="yiyi-184">SQLite 扩展可以定义新的函数、 聚合或全新的虚拟表实现。</span><span class="yiyi-st" id="yiyi-185">有一个知名的扩展是一个和SQLite一起分发的全文搜索扩展。</span></p><p><span class="yiyi-st" id="yiyi-186">默认情况下禁用加载扩展。</span><span class="yiyi-st" id="yiyi-187">请参见<a class="footnote-reference" href="#f1" id="id1">[1]</a>。</span></p><div class="versionadded"><p><span class="yiyi-st" id="yiyi-188"><span class="versionmodified">版本3.2中的新功能。</span></span></p></div><pre><code class="language-python"><span></span><span class="kn">import</span> <span class="nn">sqlite3</span>
<span class="n">con</span> <span class="o">=</span> <span class="n">sqlite3</span><span class="o">.</span><span class="n">connect</span><span class="p">(</span><span class="s2">":memory:"</span><span class="p">)</span>
<span class="c1"># enable extension loading</span>
<span class="n">con</span><span class="o">.</span><span class="n">enable_load_extension</span><span class="p">(</span><span class="kc">True</span><span class="p">)</span>
<span class="c1"># Load the fulltext search extension</span>
<span class="n">con</span><span class="o">.</span><span class="n">execute</span><span class="p">(</span><span class="s2">"select load_extension('./fts3.so')"</span><span class="p">)</span>
<span class="c1"># alternatively you can load the extension using an API call:</span>
<span class="c1"># con.load_extension("./fts3.so")</span>
<span class="c1"># disable extension laoding again</span>
<span class="n">con</span><span class="o">.</span><span class="n">enable_load_extension</span><span class="p">(</span><span class="kc">False</span><span class="p">)</span>
<span class="c1"># example from SQLite wiki</span>
<span class="n">con</span><span class="o">.</span><span class="n">execute</span><span class="p">(</span><span class="s2">"create virtual table recipe using fts3(name, ingredients)"</span><span class="p">)</span>
<span class="n">con</span><span class="o">.</span><span class="n">executescript</span><span class="p">(</span><span class="s2">"""</span>
<span class="s2"> insert into recipe (name, ingredients) values ('broccoli stew', 'broccoli peppers cheese tomatoes');</span>
<span class="s2"> insert into recipe (name, ingredients) values ('pumpkin stew', 'pumpkin onions garlic celery');</span>
<span class="s2"> insert into recipe (name, ingredients) values ('broccoli pie', 'broccoli cheese onions flour');</span>
<span class="s2"> insert into recipe (name, ingredients) values ('pumpkin pie', 'pumpkin sugar flour butter');</span>
<span class="s2"> """</span><span class="p">)</span>
<span class="k">for</span> <span class="n">row</span> <span class="ow">in</span> <span class="n">con</span><span class="o">.</span><span class="n">execute</span><span class="p">(</span><span class="s2">"select rowid, name, ingredients from recipe where name match 'pie'"</span><span class="p">):</span>
<span class="nb">print</span><span class="p">(</span><span class="n">row</span><span class="p">)</span>
</code></pre></dd></dl><dl class="method"><dt id="sqlite3.Connection.load_extension"><span class="yiyi-st" id="yiyi-189"> <code class="descname">load_extension</code><span class="sig-paren">(</span><em>path</em><span class="sig-paren">)</span></span></dt><dd><p><span class="yiyi-st" id="yiyi-190">此例程从一个共享库加载 SQLite 扩展。</span><span class="yiyi-st" id="yiyi-191">在使用该方法之前必须用<a class="reference internal" href="#sqlite3.Connection.enable_load_extension" title="sqlite3.Connection.enable_load_extension"><code class="xref py py-meth docutils literal"><span class="pre">enable_load_extension()</span></code></a>来允许扩展加载。</span></p><p><span class="yiyi-st" id="yiyi-192">默认情况下禁用加载扩展。</span><span class="yiyi-st" id="yiyi-193">请参见<a class="footnote-reference" href="#f1" id="id2">[1]</a>。</span></p><div class="versionadded"><p><span class="yiyi-st" id="yiyi-194"><span class="versionmodified">版本3.2中的新功能。</span></span></p></div></dd></dl><dl class="attribute"><dt id="sqlite3.Connection.row_factory"><span class="yiyi-st" id="yiyi-195"> <code class="descname">row_factory</code></span></dt><dd><p><span class="yiyi-st" id="yiyi-196">可以将此属性修改为一可调用对象，该对象接收游标和原始行作为参数，返回真正的结果行。</span><span class="yiyi-st" id="yiyi-197">以这种方式，你可以实现更高级的返回结果的方式，比如返回一个对象，可以通过按列名的方式来访问列。</span></p><p><span class="yiyi-st" id="yiyi-198">示例：</span></p><pre><code class="language-python"><span></span><span class="kn">import</span> <span class="nn">sqlite3</span>
<span class="k">def</span> <span class="nf">dict_factory</span><span class="p">(</span><span class="n">cursor</span><span class="p">,</span> <span class="n">row</span><span class="p">):</span>
<span class="n">d</span> <span class="o">=</span> <span class="p">{}</span>
<span class="k">for</span> <span class="n">idx</span><span class="p">,</span> <span class="n">col</span> <span class="ow">in</span> <span class="nb">enumerate</span><span class="p">(</span><span class="n">cursor</span><span class="o">.</span><span class="n">description</span><span class="p">):</span>
<span class="n">d</span><span class="p">[</span><span class="n">col</span><span class="p">[</span><span class="mi">0</span><span class="p">]]</span> <span class="o">=</span> <span class="n">row</span><span class="p">[</span><span class="n">idx</span><span class="p">]</span>
<span class="k">return</span> <span class="n">d</span>
<span class="n">con</span> <span class="o">=</span> <span class="n">sqlite3</span><span class="o">.</span><span class="n">connect</span><span class="p">(</span><span class="s2">":memory:"</span><span class="p">)</span>
<span class="n">con</span><span class="o">.</span><span class="n">row_factory</span> <span class="o">=</span> <span class="n">dict_factory</span>
<span class="n">cur</span> <span class="o">=</span> <span class="n">con</span><span class="o">.</span><span class="n">cursor</span><span class="p">()</span>
<span class="n">cur</span><span class="o">.</span><span class="n">execute</span><span class="p">(</span><span class="s2">"select 1 as a"</span><span class="p">)</span>
<span class="nb">print</span><span class="p">(</span><span class="n">cur</span><span class="o">.</span><span class="n">fetchone</span><span class="p">()[</span><span class="s2">"a"</span><span class="p">])</span>
</code></pre><p><span class="yiyi-st" id="yiyi-199">如果返回元组不够，并且您希望基于名称访问列，则应考虑将<a class="reference internal" href="#sqlite3.Connection.row_factory" title="sqlite3.Connection.row_factory"><code class="xref py py-attr docutils literal"><span class="pre">row_factory</span></code></a>设置为高度优化的<a class="reference internal" href="#sqlite3.Row" title="sqlite3.Row"><code class="xref py py-class docutils literal"><span class="pre">sqlite3.Row</span></code></a>类型。</span><span class="yiyi-st" id="yiyi-200"><a class="reference internal" href="#sqlite3.Row" title="sqlite3.Row"><code class="xref py py-class docutils literal"><span class="pre">Row</span></code></a>提供了基于索引的方式来访问列，也提供了基于大小写无关的名字的方式来访问列，且几乎没有内存的额外开销。</span><span class="yiyi-st" id="yiyi-201">它一般都会比你自定义的基于字典的方案甚至基于db_row的方案要好。</span></p></dd></dl><dl class="attribute"><dt id="sqlite3.Connection.text_factory"><span class="yiyi-st" id="yiyi-202"> <code class="descname">text_factory</code></span></dt><dd><p><span class="yiyi-st" id="yiyi-203">使用此属性可以控制对于<code class="docutils literal"><span class="pre">TEXT</span></code>数据类型，何种对象将会返回。</span><span class="yiyi-st" id="yiyi-204">默认情况下，此属性设置为<a class="reference internal" href="stdtypes.html#str" title="str"><code class="xref py py-class docutils literal"><span class="pre">str</span></code></a>，而<a class="reference internal" href="#module-sqlite3" title="sqlite3: A DB-API 2.0 implementation using SQLite 3.x."><code class="xref py py-mod docutils literal"><span class="pre">sqlite3</span></code></a>模块将返回<code class="docutils literal"><span class="pre">TEXT</span></code>的Unicode对象。</span><span class="yiyi-st" id="yiyi-205">如果要返回bytestrings，可以将其设置为<a class="reference internal" href="functions.html#bytes" title="bytes"><code class="xref py py-class docutils literal"><span class="pre">bytes</span></code></a>。</span></p><p><span class="yiyi-st" id="yiyi-206">也可以将其设置为任意的其它的可调用对象，该对象接收单一的bytestring参数，返回结果对象。</span></p><p><span class="yiyi-st" id="yiyi-207">请参见下面的演示例子代码：</span></p><pre><code class="language-python"><span></span><span class="kn">import</span> <span class="nn">sqlite3</span>
<span class="n">con</span> <span class="o">=</span> <span class="n">sqlite3</span><span class="o">.</span><span class="n">connect</span><span class="p">(</span><span class="s2">":memory:"</span><span class="p">)</span>
<span class="n">cur</span> <span class="o">=</span> <span class="n">con</span><span class="o">.</span><span class="n">cursor</span><span class="p">()</span>
<span class="n">AUSTRIA</span> <span class="o">=</span> <span class="s2">"</span><span class="se">\xd6</span><span class="s2">sterreich"</span>
<span class="c1"># by default, rows are returned as Unicode</span>
<span class="n">cur</span><span class="o">.</span><span class="n">execute</span><span class="p">(</span><span class="s2">"select ?"</span><span class="p">,</span> <span class="p">(</span><span class="n">AUSTRIA</span><span class="p">,))</span>
<span class="n">row</span> <span class="o">=</span> <span class="n">cur</span><span class="o">.</span><span class="n">fetchone</span><span class="p">()</span>
<span class="k">assert</span> <span class="n">row</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span> <span class="o">==</span> <span class="n">AUSTRIA</span>
<span class="c1"># but we can make sqlite3 always return bytestrings ...</span>
<span class="n">con</span><span class="o">.</span><span class="n">text_factory</span> <span class="o">=</span> <span class="nb">bytes</span>
<span class="n">cur</span><span class="o">.</span><span class="n">execute</span><span class="p">(</span><span class="s2">"select ?"</span><span class="p">,</span> <span class="p">(</span><span class="n">AUSTRIA</span><span class="p">,))</span>
<span class="n">row</span> <span class="o">=</span> <span class="n">cur</span><span class="o">.</span><span class="n">fetchone</span><span class="p">()</span>
<span class="k">assert</span> <span class="nb">type</span><span class="p">(</span><span class="n">row</span><span class="p">[</span><span class="mi">0</span><span class="p">])</span> <span class="ow">is</span> <span class="nb">bytes</span>
<span class="c1"># the bytestrings will be encoded in UTF-8, unless you stored garbage in the</span>
<span class="c1"># database ...</span>
<span class="k">assert</span> <span class="n">row</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span> <span class="o">==</span> <span class="n">AUSTRIA</span><span class="o">.</span><span class="n">encode</span><span class="p">(</span><span class="s2">"utf-8"</span><span class="p">)</span>
<span class="c1"># we can also implement a custom text_factory ...</span>
<span class="c1"># here we implement one that appends "foo" to all strings</span>
<span class="n">con</span><span class="o">.</span><span class="n">text_factory</span> <span class="o">=</span> <span class="k">lambda</span> <span class="n">x</span><span class="p">:</span> <span class="n">x</span><span class="o">.</span><span class="n">decode</span><span class="p">(</span><span class="s2">"utf-8"</span><span class="p">)</span> <span class="o">+</span> <span class="s2">"foo"</span>
<span class="n">cur</span><span class="o">.</span><span class="n">execute</span><span class="p">(</span><span class="s2">"select ?"</span><span class="p">,</span> <span class="p">(</span><span class="s2">"bar"</span><span class="p">,))</span>
<span class="n">row</span> <span class="o">=</span> <span class="n">cur</span><span class="o">.</span><span class="n">fetchone</span><span class="p">()</span>
<span class="k">assert</span> <span class="n">row</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span> <span class="o">==</span> <span class="s2">"barfoo"</span>
</code></pre></dd></dl><dl class="attribute"><dt id="sqlite3.Connection.total_changes"><span class="yiyi-st" id="yiyi-208"> <code class="descname">total_changes</code></span></dt><dd><p><span class="yiyi-st" id="yiyi-209">返回自从数据库连接打开以来，所有的被修改的／添加的／删除的数据行的数目。</span></p></dd></dl><dl class="method"><dt id="sqlite3.Connection.iterdump"><span class="yiyi-st" id="yiyi-210"> <code class="descname">iterdump</code><span class="sig-paren">(</span><span class="sig-paren">)</span></span></dt><dd><p><span class="yiyi-st" id="yiyi-211">返回一个以SQL文本格式转储数据的迭代器。</span><span class="yiyi-st" id="yiyi-212">保存内存中的数据库，供以后还原时很有用。</span><span class="yiyi-st" id="yiyi-213">此函数提供<strong class="program">sqlite3</strong> shell中<code class="kbd docutils literal"><span class="pre">.dump</span></code>命令相同的功能。</span></p><p><span class="yiyi-st" id="yiyi-214">示例：</span></p><pre><code class="language-python"><span></span><span class="c1"># Convert file existing_db.db to SQL dump file dump.sql</span>
<span class="kn">import</span> <span class="nn">sqlite3</span>
<span class="n">con</span> <span class="o">=</span> <span class="n">sqlite3</span><span class="o">.</span><span class="n">connect</span><span class="p">(</span><span class="s1">'existing_db.db'</span><span class="p">)</span>
<span class="k">with</span> <span class="nb">open</span><span class="p">(</span><span class="s1">'dump.sql'</span><span class="p">,</span> <span class="s1">'w'</span><span class="p">)</span> <span class="k">as</span> <span class="n">f</span><span class="p">:</span>
<span class="k">for</span> <span class="n">line</span> <span class="ow">in</span> <span class="n">con</span><span class="o">.</span><span class="n">iterdump</span><span class="p">():</span>
<span class="n">f</span><span class="o">.</span><span class="n">write</span><span class="p">(</span><span class="s1">'</span><span class="si">%s</span><span class="se">\n</span><span class="s1">'</span> <span class="o">%</span> <span class="n">line</span><span class="p">)</span>
</code></pre></dd></dl></dd></dl></div><div class="section" id="cursor-objects"><h2><span class="yiyi-st" id="yiyi-215">12.6.3. </span><span class="yiyi-st" id="yiyi-216">Cursor Objects</span></h2><dl class="class"><dt id="sqlite3.Cursor"><span class="yiyi-st" id="yiyi-217"> <em class="property">class </em><code class="descclassname">sqlite3.</code><code class="descname">Cursor</code></span></dt><dd><p><span class="yiyi-st" id="yiyi-218"><a class="reference internal" href="#sqlite3.Cursor" title="sqlite3.Cursor"><code class="xref py py-class docutils literal"><span class="pre">Cursor</span></code></a>实例具有以下的属性和方法。</span></p><dl class="method"><dt id="sqlite3.Cursor.execute"><span class="yiyi-st" id="yiyi-219"> <code class="descname">execute</code><span class="sig-paren">(</span><em>sql</em><span class="optional">[</span>, <em>parameters</em><span class="optional">]</span><span class="sig-paren">)</span></span></dt><dd><p><span class="yiyi-st" id="yiyi-220">执行一个 SQL 语句。</span><span class="yiyi-st" id="yiyi-221">SQL语句可以参数化（即使用占位符而不是SQL字面量）。</span><span class="yiyi-st" id="yiyi-222"><a class="reference internal" href="#module-sqlite3" title="sqlite3: A DB-API 2.0 implementation using SQLite 3.x."><code class="xref py py-mod docutils literal"><span class="pre">sqlite3</span></code></a>模块支持两种类型的占位符：问号标记（qmark 型） 和命名占位符 （命名样式）。</span></p><p><span class="yiyi-st" id="yiyi-223">这里是两种风格的示例：</span></p><pre><code class="language-python"><span></span><span class="kn">import</span> <span class="nn">sqlite3</span>
<span class="n">con</span> <span class="o">=</span> <span class="n">sqlite3</span><span class="o">.</span><span class="n">connect</span><span class="p">(</span><span class="s2">":memory:"</span><span class="p">)</span>
<span class="n">cur</span> <span class="o">=</span> <span class="n">con</span><span class="o">.</span><span class="n">cursor</span><span class="p">()</span>
<span class="n">cur</span><span class="o">.</span><span class="n">execute</span><span class="p">(</span><span class="s2">"create table people (name_last, age)"</span><span class="p">)</span>
<span class="n">who</span> <span class="o">=</span> <span class="s2">"Yeltsin"</span>
<span class="n">age</span> <span class="o">=</span> <span class="mi">72</span>
<span class="c1"># This is the qmark style:</span>
<span class="n">cur</span><span class="o">.</span><span class="n">execute</span><span class="p">(</span><span class="s2">"insert into people values (?, ?)"</span><span class="p">,</span> <span class="p">(</span><span class="n">who</span><span class="p">,</span> <span class="n">age</span><span class="p">))</span>
<span class="c1"># And this is the named style:</span>
<span class="n">cur</span><span class="o">.</span><span class="n">execute</span><span class="p">(</span><span class="s2">"select * from people where name_last=:who and age=:age"</span><span class="p">,</span> <span class="p">{</span><span class="s2">"who"</span><span class="p">:</span> <span class="n">who</span><span class="p">,</span> <span class="s2">"age"</span><span class="p">:</span> <span class="n">age</span><span class="p">})</span>
<span class="nb">print</span><span class="p">(</span><span class="n">cur</span><span class="o">.</span><span class="n">fetchone</span><span class="p">())</span>
</code></pre><p><span class="yiyi-st" id="yiyi-224"><a class="reference internal" href="#sqlite3.Cursor.execute" title="sqlite3.Cursor.execute"><code class="xref py py-meth docutils literal"><span class="pre">execute()</span></code></a>只执行单个 SQL 语句。</span><span class="yiyi-st" id="yiyi-225">如果您尝试使用它执行多个语句，它将引发<code class="docutils literal"><span class="pre">sqlite3.Warning</span></code>。</span><span class="yiyi-st" id="yiyi-226">如果想要在一个调用中执行多个 SQL 语句，请使用<a class="reference internal" href="#sqlite3.Cursor.executescript" title="sqlite3.Cursor.executescript"><code class="xref py py-meth docutils literal"><span class="pre">executescript()</span></code></a> 。</span></p></dd></dl><dl class="method"><dt id="sqlite3.Cursor.executemany"><span class="yiyi-st" id="yiyi-227"> <code class="descname">executemany</code><span class="sig-paren">(</span><em>sql</em>, <em>seq_of_parameters</em><span class="sig-paren">)</span></span></dt><dd><p><span class="yiyi-st" id="yiyi-228">对在序列<em>seq_of_parameters</em>中找到的所有参数序列或映射执行SQL命令。</span><span class="yiyi-st" id="yiyi-229">除了序列，<a class="reference internal" href="#module-sqlite3" title="sqlite3: A DB-API 2.0 implementation using SQLite 3.x."><code class="xref py py-mod docutils literal"><span class="pre">sqlite3</span></code></a>模块也允许使用<a class="reference internal" href="../glossary.html#term-iterator"><span class="xref std std-term">iterator</span></a> yield 参数。</span></p><pre><code class="language-python"><span></span><span class="kn">import</span> <span class="nn">sqlite3</span>
<span class="k">class</span> <span class="nc">IterChars</span><span class="p">:</span>
<span class="k">def</span> <span class="nf">__init__</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="bp">self</span><span class="o">.</span><span class="n">count</span> <span class="o">=</span> <span class="nb">ord</span><span class="p">(</span><span class="s1">'a'</span><span class="p">)</span>
<span class="k">def</span> <span class="nf">__iter__</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="k">return</span> <span class="bp">self</span>
<span class="k">def</span> <span class="nf">__next__</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="k">if</span> <span class="bp">self</span><span class="o">.</span><span class="n">count</span> <span class="o">&gt;</span> <span class="nb">ord</span><span class="p">(</span><span class="s1">'z'</span><span class="p">):</span>
<span class="k">raise</span> <span class="ne">StopIteration</span>
<span class="bp">self</span><span class="o">.</span><span class="n">count</span> <span class="o">+=</span> <span class="mi">1</span>
<span class="k">return</span> <span class="p">(</span><span class="nb">chr</span><span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="n">count</span> <span class="o">-</span> <span class="mi">1</span><span class="p">),)</span> <span class="c1"># this is a 1-tuple</span>
<span class="n">con</span> <span class="o">=</span> <span class="n">sqlite3</span><span class="o">.</span><span class="n">connect</span><span class="p">(</span><span class="s2">":memory:"</span><span class="p">)</span>
<span class="n">cur</span> <span class="o">=</span> <span class="n">con</span><span class="o">.</span><span class="n">cursor</span><span class="p">()</span>
<span class="n">cur</span><span class="o">.</span><span class="n">execute</span><span class="p">(</span><span class="s2">"create table characters(c)"</span><span class="p">)</span>
<span class="n">theIter</span> <span class="o">=</span> <span class="n">IterChars</span><span class="p">()</span>
<span class="n">cur</span><span class="o">.</span><span class="n">executemany</span><span class="p">(</span><span class="s2">"insert into characters(c) values (?)"</span><span class="p">,</span> <span class="n">theIter</span><span class="p">)</span>
<span class="n">cur</span><span class="o">.</span><span class="n">execute</span><span class="p">(</span><span class="s2">"select c from characters"</span><span class="p">)</span>
<span class="nb">print</span><span class="p">(</span><span class="n">cur</span><span class="o">.</span><span class="n">fetchall</span><span class="p">())</span>
</code></pre><p><span class="yiyi-st" id="yiyi-230">这里是使用一种<a class="reference internal" href="../glossary.html#term-generator"><span class="xref std std-term">generator</span></a>的更短的示例：</span></p><pre><code class="language-python"><span></span><span class="kn">import</span> <span class="nn">sqlite3</span>
<span class="kn">import</span> <span class="nn">string</span>
<span class="k">def</span> <span class="nf">char_generator</span><span class="p">():</span>
<span class="k">for</span> <span class="n">c</span> <span class="ow">in</span> <span class="n">string</span><span class="o">.</span><span class="n">ascii_lowercase</span><span class="p">:</span>
<span class="k">yield</span> <span class="p">(</span><span class="n">c</span><span class="p">,)</span>
<span class="n">con</span> <span class="o">=</span> <span class="n">sqlite3</span><span class="o">.</span><span class="n">connect</span><span class="p">(</span><span class="s2">":memory:"</span><span class="p">)</span>
<span class="n">cur</span> <span class="o">=</span> <span class="n">con</span><span class="o">.</span><span class="n">cursor</span><span class="p">()</span>
<span class="n">cur</span><span class="o">.</span><span class="n">execute</span><span class="p">(</span><span class="s2">"create table characters(c)"</span><span class="p">)</span>
<span class="n">cur</span><span class="o">.</span><span class="n">executemany</span><span class="p">(</span><span class="s2">"insert into characters(c) values (?)"</span><span class="p">,</span> <span class="n">char_generator</span><span class="p">())</span>
<span class="n">cur</span><span class="o">.</span><span class="n">execute</span><span class="p">(</span><span class="s2">"select c from characters"</span><span class="p">)</span>
<span class="nb">print</span><span class="p">(</span><span class="n">cur</span><span class="o">.</span><span class="n">fetchall</span><span class="p">())</span>
</code></pre></dd></dl><dl class="method"><dt id="sqlite3.Cursor.executescript"><span class="yiyi-st" id="yiyi-231"> <code class="descname">executescript</code><span class="sig-paren">(</span><em>sql_script</em><span class="sig-paren">)</span></span></dt><dd><p><span class="yiyi-st" id="yiyi-232">这是一次执行多个 SQL 语句的非标准的便捷方法。</span><span class="yiyi-st" id="yiyi-233">它先发出<code class="docutils literal"><span class="pre">COMMIT</span></code>语句，然后执行作为参数的 SQL 脚本。</span></p><p><span class="yiyi-st" id="yiyi-234"><em>sql_script</em>可以是<a class="reference internal" href="stdtypes.html#str" title="str"><code class="xref py py-class docutils literal"><span class="pre">str</span></code></a>的实例。</span></p><p><span class="yiyi-st" id="yiyi-235">示例：</span></p><pre><code class="language-python"><span></span><span class="kn">import</span> <span class="nn">sqlite3</span>
<span class="n">con</span> <span class="o">=</span> <span class="n">sqlite3</span><span class="o">.</span><span class="n">connect</span><span class="p">(</span><span class="s2">":memory:"</span><span class="p">)</span>
<span class="n">cur</span> <span class="o">=</span> <span class="n">con</span><span class="o">.</span><span class="n">cursor</span><span class="p">()</span>
<span class="n">cur</span><span class="o">.</span><span class="n">executescript</span><span class="p">(</span><span class="s2">"""</span>
<span class="s2"> create table person(</span>
<span class="s2"> firstname,</span>
<span class="s2"> lastname,</span>
<span class="s2"> age</span>
<span class="s2"> );</span>
<span class="s2"> create table book(</span>
<span class="s2"> title,</span>
<span class="s2"> author,</span>
<span class="s2"> published</span>
<span class="s2"> );</span>
<span class="s2"> insert into book(title, author, published)</span>
<span class="s2"> values (</span>
<span class="s2"> 'Dirk Gently''s Holistic Detective Agency',</span>
<span class="s2"> 'Douglas Adams',</span>
<span class="s2"> 1987</span>
<span class="s2"> );</span>
<span class="s2"> """</span><span class="p">)</span>
</code></pre></dd></dl><dl class="method"><dt id="sqlite3.Cursor.fetchone"><span class="yiyi-st" id="yiyi-236"> <code class="descname">fetchone</code><span class="sig-paren">(</span><span class="sig-paren">)</span></span></dt><dd><p><span class="yiyi-st" id="yiyi-237">获取查询结果集的下一行，返回单一序列，如果没有数据可用，返回<a class="reference internal" href="constants.html#None" title="None"><code class="xref py py-const docutils literal"><span class="pre">None</span></code></a>。</span></p></dd></dl><dl class="method"><dt id="sqlite3.Cursor.fetchmany"><span class="yiyi-st" id="yiyi-238"> <code class="descname">fetchmany</code><span class="sig-paren">(</span><em>size=cursor.arraysize</em><span class="sig-paren">)</span></span></dt><dd><p><span class="yiyi-st" id="yiyi-239">获取查询结果的下一组行，返回一个列表。</span><span class="yiyi-st" id="yiyi-240">没有更多行时，将返回空的列表。</span></p><p><span class="yiyi-st" id="yiyi-241">由<em>size</em>参数指定每次调用需要获取的行数。</span><span class="yiyi-st" id="yiyi-242">如果它不给，游标的 arraysize 确定要读取的行数。</span><span class="yiyi-st" id="yiyi-243">该方法设法获取尽可能多的，由size参数所示数目的行。</span><span class="yiyi-st" id="yiyi-244">如果这不可行（由于指定数目的行不可用），可能会返回较少行数。</span></p><p><span class="yiyi-st" id="yiyi-245">请注意关于<em>size</em>参数有性能上的考量。</span><span class="yiyi-st" id="yiyi-246">为获得最佳性能，通常最好使用 arraysize 属性。</span><span class="yiyi-st" id="yiyi-247">如果使用<em>size</em>参数，最好每次调用<a class="reference internal" href="#sqlite3.Cursor.fetchmany" title="sqlite3.Cursor.fetchmany"><code class="xref py py-meth docutils literal"><span class="pre">fetchmany()</span></code></a>都用相同的值。</span></p></dd></dl><dl class="method"><dt id="sqlite3.Cursor.fetchall"><span class="yiyi-st" id="yiyi-248"> <code class="descname">fetchall</code><span class="sig-paren">(</span><span class="sig-paren">)</span></span></dt><dd><p><span class="yiyi-st" id="yiyi-249">获取查询结果的所有（剩余）行，返回一个列表。</span><span class="yiyi-st" id="yiyi-250">请注意游标的 arraysize 属性可以影响此操作的性能。</span><span class="yiyi-st" id="yiyi-251">没有行可用时，则返回一个空列表。</span></p></dd></dl><dl class="method"><dt id="sqlite3.Cursor.close"><span class="yiyi-st" id="yiyi-252"> <code class="descname">close</code><span class="sig-paren">(</span><span class="sig-paren">)</span></span></dt><dd><p><span class="yiyi-st" id="yiyi-253">现在关闭光标（而不是每次调用<code class="docutils literal"><span class="pre">__del__</span></code>时）。</span></p><p><span class="yiyi-st" id="yiyi-254">光标将从这一点向前不可用；如果使用光标进行任何操作，则会出现<code class="docutils literal"><span class="pre">ProgrammingError</span></code>异常。</span></p></dd></dl><dl class="attribute"><dt id="sqlite3.Cursor.rowcount"><span class="yiyi-st" id="yiyi-255"> <code class="descname">rowcount</code></span></dt><dd><p><span class="yiyi-st" id="yiyi-256">虽然<a class="reference internal" href="#sqlite3.Cursor" title="sqlite3.Cursor"><code class="xref py py-class docutils literal"><span class="pre">sql3</span></code></a>模块的<a class="reference internal" href="#module-sqlite3" title="sqlite3: A DB-API 2.0 implementation using SQLite 3.x."><code class="xref py py-mod docutils literal"><span class="pre">curcor</span></code></a>类实现了该属性，怪异的是数据库引擎自己支持如何决定"受影响行"/"被选择行"。</span></p><p><span class="yiyi-st" id="yiyi-257">对于<a class="reference internal" href="#sqlite3.Cursor.executemany" title="sqlite3.Cursor.executemany"><code class="xref py py-meth docutils literal"><span class="pre">executemany()</span></code></a>语句，修改总数被累加到<a class="reference internal" href="#sqlite3.Cursor.rowcount" title="sqlite3.Cursor.rowcount"><code class="xref py py-attr docutils literal"><span class="pre">rowcount</span></code></a>。</span></p><p><span class="yiyi-st" id="yiyi-258">根据Python DB API 规范的要求，<a class="reference internal" href="#sqlite3.Cursor.rowcount" title="sqlite3.Cursor.rowcount"><code class="xref py py-attr docutils literal"><span class="pre">rowcount</span></code></a>属性是-1， 如果在游标上没有执行<code class="docutils literal"><span class="pre">executeXX()</span></code>，或者接口无法判断上次操作的rowcount。</span><span class="yiyi-st" id="yiyi-259">这包括<code class="docutils literal"><span class="pre">SELECT</span></code>语句，因为我们无法确定查询所产生的行数，直到所有的行被获取为止。</span></p><p><span class="yiyi-st" id="yiyi-260">SQLite 3.6.5之前，如果无条件的<code class="docutils literal"><span class="pre">DELETE </span><span class="pre">FROM</span> <span class="pre">talbe</span></code>，<a class="reference internal" href="#sqlite3.Cursor.rowcount" title="sqlite3.Cursor.rowcount"><code class="xref py py-attr docutils literal"><span class="pre">rowcount</span></code></a>为 0。</span></p></dd></dl><dl class="attribute"><dt id="sqlite3.Cursor.lastrowid"><span class="yiyi-st" id="yiyi-261"> <code class="descname">lastrowid</code></span></dt><dd><p><span class="yiyi-st" id="yiyi-262">此只读属性提供最后被修改行的 rowid 。</span><span class="yiyi-st" id="yiyi-263">仅当您使用<a class="reference internal" href="#sqlite3.Cursor.execute" title="sqlite3.Cursor.execute"><code class="xref py py-meth docutils literal"><span class="pre">execute()</span></code></a>方法发出<code class="docutils literal"><span class="pre">INSERT</span></code>语句时，才会设置此选项。</span><span class="yiyi-st" id="yiyi-264">对于非<code class="docutils literal"><span class="pre">INSERT</span></code>的其它操作或调用<a class="reference internal" href="#sqlite3.Cursor.executemany" title="sqlite3.Cursor.executemany"><code class="xref py py-meth docutils literal"><span class="pre">executemany()</span></code></a>， <a class="reference internal" href="#sqlite3.Cursor.lastrowid" title="sqlite3.Cursor.lastrowid"><code class="xref py py-attr docutils literal"><span class="pre">lastrowid</span></code></a>设置为<a class="reference internal" href="constants.html#None" title="None"><code class="xref py py-const docutils literal"><span class="pre">None</span></code></a>。</span></p></dd></dl><dl class="attribute"><dt id="sqlite3.Cursor.description"><span class="yiyi-st" id="yiyi-265"> <code class="descname">description</code></span></dt><dd><p><span class="yiyi-st" id="yiyi-266">此只读属性提供最后一个查询的列名称。</span><span class="yiyi-st" id="yiyi-267">为了保持与 Python DB API 兼容，它对每一个列返回一个 7 元组，每个元组的后面的6个元素都是<a class="reference internal" href="constants.html#None" title="None"><code class="xref py py-const docutils literal"><span class="pre">None</span></code></a>。</span></p><p><span class="yiyi-st" id="yiyi-268">对于没有匹配到任何一行的<code class="docutils literal"><span class="pre">SELECT</span></code>语句该属性也被设置。</span></p></dd></dl><dl class="attribute"><dt id="sqlite3.Cursor.connection"><span class="yiyi-st" id="yiyi-269"> <code class="descname">connection</code></span></dt><dd><p><span class="yiyi-st" id="yiyi-270">此只读属性提供由<a class="reference internal" href="#sqlite3.Cursor" title="sqlite3.Cursor"><code class="xref py py-class docutils literal"><span class="pre">Cursor</span></code></a>对象使用的SQLite数据库<a class="reference internal" href="#sqlite3.Connection" title="sqlite3.Connection"><code class="xref py py-class docutils literal"><span class="pre">Connection</span></code></a>。</span><span class="yiyi-st" id="yiyi-271">通过调用<a class="reference internal" href="#sqlite3.Connection.cursor" title="sqlite3.Connection.cursor"><code class="xref py py-meth docutils literal"><span class="pre">con.cursor()</span></code></a>创建的<a class="reference internal" href="#sqlite3.Cursor" title="sqlite3.Cursor"><code class="xref py py-class docutils literal"><span class="pre">Cursor</span></code></a>对象将具有指向<em>con</em>的<a class="reference internal" href="#sqlite3.Cursor.connection" title="sqlite3.Cursor.connection"><code class="xref py py-attr docutils literal"><span class="pre">connection</span></code></a>属性：</span></p><pre><code class="language-python"><span></span><span class="gp">&gt;&gt;&gt; </span><span class="n">con</span> <span class="o">=</span> <span class="n">sqlite3</span><span class="o">.</span><span class="n">connect</span><span class="p">(</span><span class="s2">":memory:"</span><span class="p">)</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">cur</span> <span class="o">=</span> <span class="n">con</span><span class="o">.</span><span class="n">cursor</span><span class="p">()</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">cur</span><span class="o">.</span><span class="n">connection</span> <span class="o">==</span> <span class="n">con</span>
<span class="go">True</span>
</code></pre></dd></dl></dd></dl></div><div class="section" id="row-objects"><h2><span class="yiyi-st" id="yiyi-272">12.6.4. </span><span class="yiyi-st" id="yiyi-273">Row Objects</span></h2><dl class="class"><dt id="sqlite3.Row"><span class="yiyi-st" id="yiyi-274"> <em class="property">class </em><code class="descclassname">sqlite3.</code><code class="descname">Row</code></span></dt><dd><p><span class="yiyi-st" id="yiyi-275"><a class="reference internal" href="#sqlite3.Row" title="sqlite3.Row"><code class="xref py py-class docutils literal"><span class="pre">Row</span></code></a>实例作为<a class="reference internal" href="#sqlite3.Connection" title="sqlite3.Connection"><code class="xref py py-class docutils literal"><span class="pre">Connection</span></code></a>对象的高度优化的<a class="reference internal" href="#sqlite3.Connection.row_factory" title="sqlite3.Connection.row_factory"><code class="xref py py-attr docutils literal"><span class="pre">row_factory</span></code></a>。</span><span class="yiyi-st" id="yiyi-276">在大多数功能中它试图模仿一个元组。</span></p><p><span class="yiyi-st" id="yiyi-277">它支持通过列名和索引的映射访问，迭代，表现，相等性测试和<a class="reference internal" href="functions.html#len" title="len"><code class="xref py py-func docutils literal"><span class="pre">len()</span></code></a>。</span></p><p><span class="yiyi-st" id="yiyi-278">如果两个<a class="reference internal" href="#sqlite3.Row" title="sqlite3.Row"><code class="xref py py-class docutils literal"><span class="pre">Row</span></code></a>对象具有完全相同的列且它们的成员都是相等，则他们比较结果相等。</span></p><dl class="method"><dt id="sqlite3.Row.keys"><span class="yiyi-st" id="yiyi-279"> <code class="descname">keys</code><span class="sig-paren">(</span><span class="sig-paren">)</span></span></dt><dd><p><span class="yiyi-st" id="yiyi-280">此方法返回列名称的列表。</span><span class="yiyi-st" id="yiyi-281">在查询后，它是在<a class="reference internal" href="#sqlite3.Cursor.description" title="sqlite3.Cursor.description"><code class="xref py py-attr docutils literal"><span class="pre">Cursor.description</span></code></a>中每个元组的第一个成员。</span></p></dd></dl><div class="versionchanged"><p><span class="yiyi-st" id="yiyi-282"><span class="versionmodified">在版本3.5中已更改：</span>添加了切片支持。</span></p></div></dd></dl><p><span class="yiyi-st" id="yiyi-283">假定初始化一个前述例子中的表：</span></p><pre><code class="language-python"><span></span><span class="n">conn</span> <span class="o">=</span> <span class="n">sqlite3</span><span class="o">.</span><span class="n">connect</span><span class="p">(</span><span class="s2">":memory:"</span><span class="p">)</span>
<span class="n">c</span> <span class="o">=</span> <span class="n">conn</span><span class="o">.</span><span class="n">cursor</span><span class="p">()</span>
<span class="n">c</span><span class="o">.</span><span class="n">execute</span><span class="p">(</span><span class="s1">'''create table stocks</span>
<span class="s1">(date text, trans text, symbol text,</span>
<span class="s1"> qty real, price real)'''</span><span class="p">)</span>
<span class="n">c</span><span class="o">.</span><span class="n">execute</span><span class="p">(</span><span class="s2">"""insert into stocks</span>
<span class="s2"> values ('2006-01-05','BUY','RHAT',100,35.14)"""</span><span class="p">)</span>
<span class="n">conn</span><span class="o">.</span><span class="n">commit</span><span class="p">()</span>
<span class="n">c</span><span class="o">.</span><span class="n">close</span><span class="p">()</span>
</code></pre><p><span class="yiyi-st" id="yiyi-284">现在我们插入<a class="reference internal" href="#sqlite3.Row" title="sqlite3.Row"><code class="xref py py-class docutils literal"><span class="pre">Row</span></code></a>：</span></p><pre><code class="language-python"><span></span><span class="gp">&gt;&gt;&gt; </span><span class="n">conn</span><span class="o">.</span><span class="n">row_factory</span> <span class="o">=</span> <span class="n">sqlite3</span><span class="o">.</span><span class="n">Row</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">c</span> <span class="o">=</span> <span class="n">conn</span><span class="o">.</span><span class="n">cursor</span><span class="p">()</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">c</span><span class="o">.</span><span class="n">execute</span><span class="p">(</span><span class="s1">'select * from stocks'</span><span class="p">)</span>
<span class="go">&lt;sqlite3.Cursor object at 0x7f4e7dd8fa80&gt;</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">r</span> <span class="o">=</span> <span class="n">c</span><span class="o">.</span><span class="n">fetchone</span><span class="p">()</span>
<span class="gp">&gt;&gt;&gt; </span><span class="nb">type</span><span class="p">(</span><span class="n">r</span><span class="p">)</span>
<span class="go">&lt;class 'sqlite3.Row'&gt;</span>
<span class="gp">&gt;&gt;&gt; </span><span class="nb">tuple</span><span class="p">(</span><span class="n">r</span><span class="p">)</span>
<span class="go">('2006-01-05', 'BUY', 'RHAT', 100.0, 35.14)</span>
<span class="gp">&gt;&gt;&gt; </span><span class="nb">len</span><span class="p">(</span><span class="n">r</span><span class="p">)</span>
<span class="go">5</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">r</span><span class="p">[</span><span class="mi">2</span><span class="p">]</span>
<span class="go">'RHAT'</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">r</span><span class="o">.</span><span class="n">keys</span><span class="p">()</span>
<span class="go">['date', 'trans', 'symbol', 'qty', 'price']</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">r</span><span class="p">[</span><span class="s1">'qty'</span><span class="p">]</span>
<span class="go">100.0</span>
<span class="gp">&gt;&gt;&gt; </span><span class="k">for</span> <span class="n">member</span> <span class="ow">in</span> <span class="n">r</span><span class="p">:</span>
<span class="gp">... </span> <span class="nb">print</span><span class="p">(</span><span class="n">member</span><span class="p">)</span>
<span class="gp">...</span>
<span class="go">2006-01-05</span>
<span class="go">BUY</span>
<span class="go">RHAT</span>
<span class="go">100.0</span>
<span class="go">35.14</span>
</code></pre></div><div class="section" id="sqlite-and-python-types"><h2><span class="yiyi-st" id="yiyi-285">12.6.5. </span><span class="yiyi-st" id="yiyi-286">SQLite and Python types</span></h2><div class="section" id="introduction"><h3><span class="yiyi-st" id="yiyi-287">12.6.5.1. </span><span class="yiyi-st" id="yiyi-288">Introduction</span></h3><p><span class="yiyi-st" id="yiyi-289">SQLite 天然支持以下类型：<code class="docutils literal"><span class="pre">NULL</span></code>、<code class="docutils literal"><span class="pre">INTEGER</span></code>、<code class="docutils literal"><span class="pre">REAL</span></code>、<code class="docutils literal"><span class="pre">TEXT</span></code>、 <code class="docutils literal"><span class="pre">BLOB</span></code>。</span></p><p><span class="yiyi-st" id="yiyi-290">因此下述Python类型可以没有任何问题地直接发送给SQLite。</span></p><table border="1" class="docutils"><thead valign="bottom"><tr class="row-odd"><th class="head"><span class="yiyi-st" id="yiyi-291">Python类型</span></th><th class="head"><span class="yiyi-st" id="yiyi-292">SQLite类型</span></th></tr></thead><tbody valign="top"><tr class="row-even"><td><span class="yiyi-st" id="yiyi-293"><a class="reference internal" href="constants.html#None" title="None"><code class="xref py py-const docutils literal"><span class="pre">None</span></code></a></span></td><td><span class="yiyi-st" id="yiyi-294"><code class="docutils literal"><span class="pre">NULL</span></code></span></td></tr><tr class="row-odd"><td><span class="yiyi-st" id="yiyi-295"><a class="reference internal" href="functions.html#int" title="int"><code class="xref py py-class docutils literal"><span class="pre">int</span></code></a></span></td><td><span class="yiyi-st" id="yiyi-296"><code class="docutils literal"><span class="pre">INTEGER</span></code></span></td></tr><tr class="row-even"><td><span class="yiyi-st" id="yiyi-297"><a class="reference internal" href="functions.html#float" title="float"><code class="xref py py-class docutils literal"><span class="pre">float</span></code></a></span></td><td><span class="yiyi-st" id="yiyi-298"><code class="docutils literal"><span class="pre">REAL</span></code></span></td></tr><tr class="row-odd"><td><span class="yiyi-st" id="yiyi-299"><a class="reference internal" href="stdtypes.html#str" title="str"><code class="xref py py-class docutils literal"><span class="pre">str</span></code></a></span></td><td><span class="yiyi-st" id="yiyi-300"><code class="docutils literal"><span class="pre">TEXT</span></code></span></td></tr><tr class="row-even"><td><span class="yiyi-st" id="yiyi-301"><a class="reference internal" href="functions.html#bytes" title="bytes"><code class="xref py py-class docutils literal"><span class="pre">bytes</span></code></a></span></td><td><span class="yiyi-st" id="yiyi-302"><code class="docutils literal"><span class="pre">BLOB</span></code></span></td></tr></tbody></table><p><span class="yiyi-st" id="yiyi-303">默认情况下SQLite类型将这样转换成Python类型：</span></p><table border="1" class="docutils"><thead valign="bottom"><tr class="row-odd"><th class="head"><span class="yiyi-st" id="yiyi-304">SQLite类型</span></th><th class="head"><span class="yiyi-st" id="yiyi-305">Python类型</span></th></tr></thead><tbody valign="top"><tr class="row-even"><td><span class="yiyi-st" id="yiyi-306"><code class="docutils literal"><span class="pre">NULL</span></code></span></td><td><span class="yiyi-st" id="yiyi-307"><a class="reference internal" href="constants.html#None" title="None"><code class="xref py py-const docutils literal"><span class="pre">None</span></code></a></span></td></tr><tr class="row-odd"><td><span class="yiyi-st" id="yiyi-308"><code class="docutils literal"><span class="pre">INTEGER</span></code></span></td><td><span class="yiyi-st" id="yiyi-309"><a class="reference internal" href="functions.html#int" title="int"><code class="xref py py-class docutils literal"><span class="pre">int</span></code></a></span></td></tr><tr class="row-even"><td><span class="yiyi-st" id="yiyi-310"><code class="docutils literal"><span class="pre">REAL</span></code></span></td><td><span class="yiyi-st" id="yiyi-311"><a class="reference internal" href="functions.html#float" title="float"><code class="xref py py-class docutils literal"><span class="pre">float</span></code></a></span></td></tr><tr class="row-odd"><td><span class="yiyi-st" id="yiyi-312"><code class="docutils literal"><span class="pre">TEXT</span></code></span></td><td><span class="yiyi-st" id="yiyi-313">默认情况下取决于<a class="reference internal" href="#sqlite3.Connection.text_factory" title="sqlite3.Connection.text_factory"><code class="xref py py-attr docutils literal"><span class="pre">text_factory</span></code></a>，<a class="reference internal" href="stdtypes.html#str" title="str"><code class="xref py py-class docutils literal"><span class="pre">str</span></code></a></span></td></tr><tr class="row-even"><td><span class="yiyi-st" id="yiyi-314"><code class="docutils literal"><span class="pre">BLOB</span></code></span></td><td><span class="yiyi-st" id="yiyi-315"><a class="reference internal" href="functions.html#bytes" title="bytes"><code class="xref py py-class docutils literal"><span class="pre">bytes</span></code></a></span></td></tr></tbody></table><p><span class="yiyi-st" id="yiyi-316"><a class="reference internal" href="#module-sqlite3" title="sqlite3: A DB-API 2.0 implementation using SQLite 3.x."><code class="xref py py-mod docutils literal"><span class="pre">sqlite3</span></code></a>模块的类型系统可以以两种方式来扩展：通过对象适配，可以在SQLite数据库中存储其它的Python类型；通过转换器让<a class="reference internal" href="#module-sqlite3" title="sqlite3: A DB-API 2.0 implementation using SQLite 3.x."><code class="xref py py-mod docutils literal"><span class="pre">sqlite3</span></code></a>模块将SQLite类型转成不同的Python类型。</span></p></div><div class="section" id="using-adapters-to-store-additional-python-types-in-sqlite-databases"><h3><span class="yiyi-st" id="yiyi-317">12.6.5.2. </span><span class="yiyi-st" id="yiyi-318">Using adapters to store additional Python types in SQLite databases</span></h3><p><span class="yiyi-st" id="yiyi-319">如之前所述，SQLite 天然只支持有限的类型。</span><span class="yiyi-st" id="yiyi-320">要使用其他Python类型与SQLite，您必须<strong>适应</strong>它们为sqlite3模块支持的SQLite类型之一：NoneType，int，float，str，bytes。</span></p><p><span class="yiyi-st" id="yiyi-321">有两种方法，可以使<a class="reference internal" href="#module-sqlite3" title="sqlite3: A DB-API 2.0 implementation using SQLite 3.x."><code class="xref py py-mod docutils literal"><span class="pre">sqlite3</span></code></a>模块适配一个Python类型到一个支持的类型。</span></p><div class="section" id="letting-your-object-adapt-itself"><h4><span class="yiyi-st" id="yiyi-322">12.6.5.2.1. </span><span class="yiyi-st" id="yiyi-323">Letting your object adapt itself</span></h4><p><span class="yiyi-st" id="yiyi-324">这是一种好方法，如果您自己编写类。</span><span class="yiyi-st" id="yiyi-325">让我们假设您有一个像这样的类：</span></p><pre><code class="language-python"><span></span><span class="k">class</span> <span class="nc">Point</span><span class="p">:</span>
<span class="k">def</span> <span class="nf">__init__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">x</span><span class="p">,</span> <span class="n">y</span><span class="p">):</span>
<span class="bp">self</span><span class="o">.</span><span class="n">x</span><span class="p">,</span> <span class="bp">self</span><span class="o">.</span><span class="n">y</span> <span class="o">=</span> <span class="n">x</span><span class="p">,</span> <span class="n">y</span>
</code></pre><p><span class="yiyi-st" id="yiyi-326">想要在单一的 SQLite 列中存储点。</span><span class="yiyi-st" id="yiyi-327">首先得选一个支持的类型，它可以用来表示点。</span><span class="yiyi-st" id="yiyi-328">假定使用 str ，并用分号来分隔坐标。</span><span class="yiyi-st" id="yiyi-329">需要给类加一个<code class="docutils literal"><span class="pre">__conform__(self, </span> <span class="pre">protocl)</span> </code> ，该方法必须返回转换后的值。</span><span class="yiyi-st" id="yiyi-330">参数<em>protocol</em>为<code class="xref py py-class docutils literal"><span class="pre">PrepareProtocol</span></code>。</span></p><pre><code class="language-python"><span></span><span class="kn">import</span> <span class="nn">sqlite3</span>
<span class="k">class</span> <span class="nc">Point</span><span class="p">:</span>
<span class="k">def</span> <span class="nf">__init__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">x</span><span class="p">,</span> <span class="n">y</span><span class="p">):</span>
<span class="bp">self</span><span class="o">.</span><span class="n">x</span><span class="p">,</span> <span class="bp">self</span><span class="o">.</span><span class="n">y</span> <span class="o">=</span> <span class="n">x</span><span class="p">,</span> <span class="n">y</span>
<span class="k">def</span> <span class="nf">__conform__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">protocol</span><span class="p">):</span>
<span class="k">if</span> <span class="n">protocol</span> <span class="ow">is</span> <span class="n">sqlite3</span><span class="o">.</span><span class="n">PrepareProtocol</span><span class="p">:</span>
<span class="k">return</span> <span class="s2">"</span><span class="si">%f</span><span class="s2">;</span><span class="si">%f</span><span class="s2">"</span> <span class="o">%</span> <span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="n">x</span><span class="p">,</span> <span class="bp">self</span><span class="o">.</span><span class="n">y</span><span class="p">)</span>
<span class="n">con</span> <span class="o">=</span> <span class="n">sqlite3</span><span class="o">.</span><span class="n">connect</span><span class="p">(</span><span class="s2">":memory:"</span><span class="p">)</span>
<span class="n">cur</span> <span class="o">=</span> <span class="n">con</span><span class="o">.</span><span class="n">cursor</span><span class="p">()</span>
<span class="n">p</span> <span class="o">=</span> <span class="n">Point</span><span class="p">(</span><span class="mf">4.0</span><span class="p">,</span> <span class="o">-</span><span class="mf">3.2</span><span class="p">)</span>
<span class="n">cur</span><span class="o">.</span><span class="n">execute</span><span class="p">(</span><span class="s2">"select ?"</span><span class="p">,</span> <span class="p">(</span><span class="n">p</span><span class="p">,))</span>
<span class="nb">print</span><span class="p">(</span><span class="n">cur</span><span class="o">.</span><span class="n">fetchone</span><span class="p">()[</span><span class="mi">0</span><span class="p">])</span>
</code></pre></div><div class="section" id="registering-an-adapter-callable"><h4><span class="yiyi-st" id="yiyi-331">12.6.5.2.2. </span><span class="yiyi-st" id="yiyi-332">Registering an adapter callable</span></h4><p><span class="yiyi-st" id="yiyi-333">另一种可能性就是创建一个函数，它用来将类型转成字符串表现形式，然后用<a class="reference internal" href="#sqlite3.register_adapter" title="sqlite3.register_adapter"><code class="xref py py-meth docutils literal"><span class="pre">register_adapter()</span></code></a>来注册该函数。</span></p><pre><code class="language-python"><span></span><span class="kn">import</span> <span class="nn">sqlite3</span>
<span class="k">class</span> <span class="nc">Point</span><span class="p">:</span>
<span class="k">def</span> <span class="nf">__init__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">x</span><span class="p">,</span> <span class="n">y</span><span class="p">):</span>
<span class="bp">self</span><span class="o">.</span><span class="n">x</span><span class="p">,</span> <span class="bp">self</span><span class="o">.</span><span class="n">y</span> <span class="o">=</span> <span class="n">x</span><span class="p">,</span> <span class="n">y</span>
<span class="k">def</span> <span class="nf">adapt_point</span><span class="p">(</span><span class="n">point</span><span class="p">):</span>
<span class="k">return</span> <span class="s2">"</span><span class="si">%f</span><span class="s2">;</span><span class="si">%f</span><span class="s2">"</span> <span class="o">%</span> <span class="p">(</span><span class="n">point</span><span class="o">.</span><span class="n">x</span><span class="p">,</span> <span class="n">point</span><span class="o">.</span><span class="n">y</span><span class="p">)</span>
<span class="n">sqlite3</span><span class="o">.</span><span class="n">register_adapter</span><span class="p">(</span><span class="n">Point</span><span class="p">,</span> <span class="n">adapt_point</span><span class="p">)</span>
<span class="n">con</span> <span class="o">=</span> <span class="n">sqlite3</span><span class="o">.</span><span class="n">connect</span><span class="p">(</span><span class="s2">":memory:"</span><span class="p">)</span>
<span class="n">cur</span> <span class="o">=</span> <span class="n">con</span><span class="o">.</span><span class="n">cursor</span><span class="p">()</span>
<span class="n">p</span> <span class="o">=</span> <span class="n">Point</span><span class="p">(</span><span class="mf">4.0</span><span class="p">,</span> <span class="o">-</span><span class="mf">3.2</span><span class="p">)</span>
<span class="n">cur</span><span class="o">.</span><span class="n">execute</span><span class="p">(</span><span class="s2">"select ?"</span><span class="p">,</span> <span class="p">(</span><span class="n">p</span><span class="p">,))</span>
<span class="nb">print</span><span class="p">(</span><span class="n">cur</span><span class="o">.</span><span class="n">fetchone</span><span class="p">()[</span><span class="mi">0</span><span class="p">])</span>
</code></pre><p><span class="yiyi-st" id="yiyi-334"><a class="reference internal" href="#module-sqlite3" title="sqlite3: A DB-API 2.0 implementation using SQLite 3.x."><code class="xref py py-mod docutils literal"><span class="pre">sqlite3</span></code></a>模块为 Python 的内置<a class="reference internal" href="datetime.html#datetime.date" title="datetime.date"><code class="xref py py-class docutils literal"><span class="pre">datetime.date</span></code></a>和<a class="reference internal" href="datetime.html#datetime.datetime" title="datetime.datetime"><code class="xref py py-class docutils literal"><span class="pre">datetime.datetime</span></code></a>类型有两个默认适配器。</span><span class="yiyi-st" id="yiyi-335">假定想要将<a class="reference internal" href="datetime.html#datetime.datetime" title="datetime.datetime"><code class="xref py py-class docutils literal"><span class="pre">datetime.datetime</span></code></a>对象不以ISO形式存储，而是存成Unix 时间戳。</span></p><pre><code class="language-python"><span></span><span class="kn">import</span> <span class="nn">sqlite3</span>
<span class="kn">import</span> <span class="nn">datetime</span>
<span class="kn">import</span> <span class="nn">time</span>
<span class="k">def</span> <span class="nf">adapt_datetime</span><span class="p">(</span><span class="n">ts</span><span class="p">):</span>
<span class="k">return</span> <span class="n">time</span><span class="o">.</span><span class="n">mktime</span><span class="p">(</span><span class="n">ts</span><span class="o">.</span><span class="n">timetuple</span><span class="p">())</span>
<span class="n">sqlite3</span><span class="o">.</span><span class="n">register_adapter</span><span class="p">(</span><span class="n">datetime</span><span class="o">.</span><span class="n">datetime</span><span class="p">,</span> <span class="n">adapt_datetime</span><span class="p">)</span>
<span class="n">con</span> <span class="o">=</span> <span class="n">sqlite3</span><span class="o">.</span><span class="n">connect</span><span class="p">(</span><span class="s2">":memory:"</span><span class="p">)</span>
<span class="n">cur</span> <span class="o">=</span> <span class="n">con</span><span class="o">.</span><span class="n">cursor</span><span class="p">()</span>
<span class="n">now</span> <span class="o">=</span> <span class="n">datetime</span><span class="o">.</span><span class="n">datetime</span><span class="o">.</span><span class="n">now</span><span class="p">()</span>
<span class="n">cur</span><span class="o">.</span><span class="n">execute</span><span class="p">(</span><span class="s2">"select ?"</span><span class="p">,</span> <span class="p">(</span><span class="n">now</span><span class="p">,))</span>
<span class="nb">print</span><span class="p">(</span><span class="n">cur</span><span class="o">.</span><span class="n">fetchone</span><span class="p">()[</span><span class="mi">0</span><span class="p">])</span>
</code></pre></div></div><div class="section" id="converting-sqlite-values-to-custom-python-types"><h3><span class="yiyi-st" id="yiyi-336">12.6.5.3. </span><span class="yiyi-st" id="yiyi-337">Converting SQLite values to custom Python types</span></h3><p><span class="yiyi-st" id="yiyi-338">编写适配器允许将自定义Python类型转成SQLite类型。</span><span class="yiyi-st" id="yiyi-339">但是要真的有用，我们必须也提供SQLite类型转成Python类型。</span></p><p><span class="yiyi-st" id="yiyi-340">进入转换器。</span></p><p><span class="yiyi-st" id="yiyi-341">让我们回到<code class="xref py py-class docutils literal"><span class="pre">Point</span></code>类。</span><span class="yiyi-st" id="yiyi-342">在SQLite中以字符串的形式存储分号分隔的x、y坐标。</span></p><p><span class="yiyi-st" id="yiyi-343">首先定义一个转换器函数，它接收字符串参数，并从中构造一个<code class="xref py py-class docutils literal"><span class="pre">Point</span></code>对象。</span></p><div class="admonition note"><p class="first admonition-title"><span class="yiyi-st" id="yiyi-344">注</span></p><p class="last"><span class="yiyi-st" id="yiyi-345">转换器函数<strong>总是</strong>使用<a class="reference internal" href="functions.html#bytes" title="bytes"><code class="xref py py-class docutils literal"><span class="pre">bytes</span></code></a>对象调用，无论将数据类型发送到SQLite的哪种数据类型。</span></p></div><pre><code class="language-python"><span></span><span class="k">def</span> <span class="nf">convert_point</span><span class="p">(</span><span class="n">s</span><span class="p">):</span>
<span class="n">x</span><span class="p">,</span> <span class="n">y</span> <span class="o">=</span> <span class="nb">map</span><span class="p">(</span><span class="nb">float</span><span class="p">,</span> <span class="n">s</span><span class="o">.</span><span class="n">split</span><span class="p">(</span><span class="n">b</span><span class="s2">";"</span><span class="p">))</span>
<span class="k">return</span> <span class="n">Point</span><span class="p">(</span><span class="n">x</span><span class="p">,</span> <span class="n">y</span><span class="p">)</span>
</code></pre><p><span class="yiyi-st" id="yiyi-346">先在需要让<a class="reference internal" href="#module-sqlite3" title="sqlite3: A DB-API 2.0 implementation using SQLite 3.x."><code class="xref py py-mod docutils literal"><span class="pre">sqlite3</span></code></a>模块知道你从数据库中选择的实际上是个点。</span><span class="yiyi-st" id="yiyi-347">有两种方法做这件事：</span></p><ul class="simple"><li><span class="yiyi-st" id="yiyi-348">Implicitly via the declared type隐式地通过声明的类型</span></li><li><span class="yiyi-st" id="yiyi-349">Explicitly via the column name 明确地通过列名</span></li></ul><p><span class="yiyi-st" id="yiyi-350">这两种方法在<a class="reference internal" href="#sqlite3-module-contents"><span>Module functions and constants</span></a>章节中都有描述，具体在<a class="reference internal" href="#sqlite3.PARSE_DECLTYPES" title="sqlite3.PARSE_DECLTYPES"><code class="xref py py-const docutils literal"><span class="pre">PARSE_DECLTYPES</span></code></a>和<a class="reference internal" href="#sqlite3.PARSE_COLNAMES" title="sqlite3.PARSE_COLNAMES"><code class="xref py py-const docutils literal"><span class="pre">PARSE_COLNAMES</span></code></a>中。</span></p><p><span class="yiyi-st" id="yiyi-351">下面的示例阐释了这两种方法。</span></p><pre><code class="language-python"><span></span><span class="kn">import</span> <span class="nn">sqlite3</span>
<span class="k">class</span> <span class="nc">Point</span><span class="p">:</span>
<span class="k">def</span> <span class="nf">__init__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">x</span><span class="p">,</span> <span class="n">y</span><span class="p">):</span>
<span class="bp">self</span><span class="o">.</span><span class="n">x</span><span class="p">,</span> <span class="bp">self</span><span class="o">.</span><span class="n">y</span> <span class="o">=</span> <span class="n">x</span><span class="p">,</span> <span class="n">y</span>
<span class="k">def</span> <span class="nf">__repr__</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="k">return</span> <span class="s2">"(</span><span class="si">%f</span><span class="s2">;</span><span class="si">%f</span><span class="s2">)"</span> <span class="o">%</span> <span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="n">x</span><span class="p">,</span> <span class="bp">self</span><span class="o">.</span><span class="n">y</span><span class="p">)</span>
<span class="k">def</span> <span class="nf">adapt_point</span><span class="p">(</span><span class="n">point</span><span class="p">):</span>
<span class="k">return</span> <span class="p">(</span><span class="s2">"</span><span class="si">%f</span><span class="s2">;</span><span class="si">%f</span><span class="s2">"</span> <span class="o">%</span> <span class="p">(</span><span class="n">point</span><span class="o">.</span><span class="n">x</span><span class="p">,</span> <span class="n">point</span><span class="o">.</span><span class="n">y</span><span class="p">))</span><span class="o">.</span><span class="n">encode</span><span class="p">(</span><span class="s1">'ascii'</span><span class="p">)</span>
<span class="k">def</span> <span class="nf">convert_point</span><span class="p">(</span><span class="n">s</span><span class="p">):</span>
<span class="n">x</span><span class="p">,</span> <span class="n">y</span> <span class="o">=</span> <span class="nb">list</span><span class="p">(</span><span class="nb">map</span><span class="p">(</span><span class="nb">float</span><span class="p">,</span> <span class="n">s</span><span class="o">.</span><span class="n">split</span><span class="p">(</span><span class="n">b</span><span class="s2">";"</span><span class="p">)))</span>
<span class="k">return</span> <span class="n">Point</span><span class="p">(</span><span class="n">x</span><span class="p">,</span> <span class="n">y</span><span class="p">)</span>
<span class="c1"># Register the adapter</span>
<span class="n">sqlite3</span><span class="o">.</span><span class="n">register_adapter</span><span class="p">(</span><span class="n">Point</span><span class="p">,</span> <span class="n">adapt_point</span><span class="p">)</span>
<span class="c1"># Register the converter</span>
<span class="n">sqlite3</span><span class="o">.</span><span class="n">register_converter</span><span class="p">(</span><span class="s2">"point"</span><span class="p">,</span> <span class="n">convert_point</span><span class="p">)</span>
<span class="n">p</span> <span class="o">=</span> <span class="n">Point</span><span class="p">(</span><span class="mf">4.0</span><span class="p">,</span> <span class="o">-</span><span class="mf">3.2</span><span class="p">)</span>
<span class="c1">#########################</span>
<span class="c1"># 1) Using declared types</span>
<span class="n">con</span> <span class="o">=</span> <span class="n">sqlite3</span><span class="o">.</span><span class="n">connect</span><span class="p">(</span><span class="s2">":memory:"</span><span class="p">,</span> <span class="n">detect_types</span><span class="o">=</span><span class="n">sqlite3</span><span class="o">.</span><span class="n">PARSE_DECLTYPES</span><span class="p">)</span>
<span class="n">cur</span> <span class="o">=</span> <span class="n">con</span><span class="o">.</span><span class="n">cursor</span><span class="p">()</span>
<span class="n">cur</span><span class="o">.</span><span class="n">execute</span><span class="p">(</span><span class="s2">"create table test(p point)"</span><span class="p">)</span>
<span class="n">cur</span><span class="o">.</span><span class="n">execute</span><span class="p">(</span><span class="s2">"insert into test(p) values (?)"</span><span class="p">,</span> <span class="p">(</span><span class="n">p</span><span class="p">,))</span>
<span class="n">cur</span><span class="o">.</span><span class="n">execute</span><span class="p">(</span><span class="s2">"select p from test"</span><span class="p">)</span>
<span class="nb">print</span><span class="p">(</span><span class="s2">"with declared types:"</span><span class="p">,</span> <span class="n">cur</span><span class="o">.</span><span class="n">fetchone</span><span class="p">()[</span><span class="mi">0</span><span class="p">])</span>
<span class="n">cur</span><span class="o">.</span><span class="n">close</span><span class="p">()</span>
<span class="n">con</span><span class="o">.</span><span class="n">close</span><span class="p">()</span>
<span class="c1">#######################</span>
<span class="c1"># 1) Using column names</span>
<span class="n">con</span> <span class="o">=</span> <span class="n">sqlite3</span><span class="o">.</span><span class="n">connect</span><span class="p">(</span><span class="s2">":memory:"</span><span class="p">,</span> <span class="n">detect_types</span><span class="o">=</span><span class="n">sqlite3</span><span class="o">.</span><span class="n">PARSE_COLNAMES</span><span class="p">)</span>
<span class="n">cur</span> <span class="o">=</span> <span class="n">con</span><span class="o">.</span><span class="n">cursor</span><span class="p">()</span>
<span class="n">cur</span><span class="o">.</span><span class="n">execute</span><span class="p">(</span><span class="s2">"create table test(p)"</span><span class="p">)</span>
<span class="n">cur</span><span class="o">.</span><span class="n">execute</span><span class="p">(</span><span class="s2">"insert into test(p) values (?)"</span><span class="p">,</span> <span class="p">(</span><span class="n">p</span><span class="p">,))</span>
<span class="n">cur</span><span class="o">.</span><span class="n">execute</span><span class="p">(</span><span class="s1">'select p as "p [point]" from test'</span><span class="p">)</span>
<span class="nb">print</span><span class="p">(</span><span class="s2">"with column names:"</span><span class="p">,</span> <span class="n">cur</span><span class="o">.</span><span class="n">fetchone</span><span class="p">()[</span><span class="mi">0</span><span class="p">])</span>
<span class="n">cur</span><span class="o">.</span><span class="n">close</span><span class="p">()</span>
<span class="n">con</span><span class="o">.</span><span class="n">close</span><span class="p">()</span>
</code></pre></div><div class="section" id="default-adapters-and-converters"><h3><span class="yiyi-st" id="yiyi-352">12.6.5.4. </span><span class="yiyi-st" id="yiyi-353">Default adapters and converters</span></h3><p><span class="yiyi-st" id="yiyi-354">在datetime模块中有对date和datetime类型的默认的适配器。</span><span class="yiyi-st" id="yiyi-355">它们将ISO dates／ISO timestamps发送给SQLite。</span></p><p><span class="yiyi-st" id="yiyi-356">默认的转换器以"date"为名注册给<a class="reference internal" href="datetime.html#datetime.date" title="datetime.date"><code class="xref py py-class docutils literal"><span class="pre">datetime.date</span></code></a>，以"timestamp"为名注册给<a class="reference internal" href="datetime.html#datetime.datetime" title="datetime.datetime"><code class="xref py py-class docutils literal"><span class="pre">datetime.datetime</span></code></a>。</span></p><p><span class="yiyi-st" id="yiyi-357">这样，在大多数情况下可以在Python中使用date／timestamp而不需要额外的动作。</span><span class="yiyi-st" id="yiyi-358">适配器的格式兼容于SQLite实际上的date/time函数。</span></p><p><span class="yiyi-st" id="yiyi-359">下面的示例演示这点。</span></p><pre><code class="language-python"><span></span><span class="kn">import</span> <span class="nn">sqlite3</span>
<span class="kn">import</span> <span class="nn">datetime</span>
<span class="n">con</span> <span class="o">=</span> <span class="n">sqlite3</span><span class="o">.</span><span class="n">connect</span><span class="p">(</span><span class="s2">":memory:"</span><span class="p">,</span> <span class="n">detect_types</span><span class="o">=</span><span class="n">sqlite3</span><span class="o">.</span><span class="n">PARSE_DECLTYPES</span><span class="o">|</span><span class="n">sqlite3</span><span class="o">.</span><span class="n">PARSE_COLNAMES</span><span class="p">)</span>
<span class="n">cur</span> <span class="o">=</span> <span class="n">con</span><span class="o">.</span><span class="n">cursor</span><span class="p">()</span>
<span class="n">cur</span><span class="o">.</span><span class="n">execute</span><span class="p">(</span><span class="s2">"create table test(d date, ts timestamp)"</span><span class="p">)</span>
<span class="n">today</span> <span class="o">=</span> <span class="n">datetime</span><span class="o">.</span><span class="n">date</span><span class="o">.</span><span class="n">today</span><span class="p">()</span>
<span class="n">now</span> <span class="o">=</span> <span class="n">datetime</span><span class="o">.</span><span class="n">datetime</span><span class="o">.</span><span class="n">now</span><span class="p">()</span>
<span class="n">cur</span><span class="o">.</span><span class="n">execute</span><span class="p">(</span><span class="s2">"insert into test(d, ts) values (?, ?)"</span><span class="p">,</span> <span class="p">(</span><span class="n">today</span><span class="p">,</span> <span class="n">now</span><span class="p">))</span>
<span class="n">cur</span><span class="o">.</span><span class="n">execute</span><span class="p">(</span><span class="s2">"select d, ts from test"</span><span class="p">)</span>
<span class="n">row</span> <span class="o">=</span> <span class="n">cur</span><span class="o">.</span><span class="n">fetchone</span><span class="p">()</span>
<span class="nb">print</span><span class="p">(</span><span class="n">today</span><span class="p">,</span> <span class="s2">"=&gt;"</span><span class="p">,</span> <span class="n">row</span><span class="p">[</span><span class="mi">0</span><span class="p">],</span> <span class="nb">type</span><span class="p">(</span><span class="n">row</span><span class="p">[</span><span class="mi">0</span><span class="p">]))</span>
<span class="nb">print</span><span class="p">(</span><span class="n">now</span><span class="p">,</span> <span class="s2">"=&gt;"</span><span class="p">,</span> <span class="n">row</span><span class="p">[</span><span class="mi">1</span><span class="p">],</span> <span class="nb">type</span><span class="p">(</span><span class="n">row</span><span class="p">[</span><span class="mi">1</span><span class="p">]))</span>
<span class="n">cur</span><span class="o">.</span><span class="n">execute</span><span class="p">(</span><span class="s1">'select current_date as "d [date]", current_timestamp as "ts [timestamp]"'</span><span class="p">)</span>
<span class="n">row</span> <span class="o">=</span> <span class="n">cur</span><span class="o">.</span><span class="n">fetchone</span><span class="p">()</span>
<span class="nb">print</span><span class="p">(</span><span class="s2">"current_date"</span><span class="p">,</span> <span class="n">row</span><span class="p">[</span><span class="mi">0</span><span class="p">],</span> <span class="nb">type</span><span class="p">(</span><span class="n">row</span><span class="p">[</span><span class="mi">0</span><span class="p">]))</span>
<span class="nb">print</span><span class="p">(</span><span class="s2">"current_timestamp"</span><span class="p">,</span> <span class="n">row</span><span class="p">[</span><span class="mi">1</span><span class="p">],</span> <span class="nb">type</span><span class="p">(</span><span class="n">row</span><span class="p">[</span><span class="mi">1</span><span class="p">]))</span>
</code></pre><p><span class="yiyi-st" id="yiyi-360">如果存储在SQLite中的时间戳的小数部分大于6个数字，它的值将由时间戳转换器截断至微秒的精度。</span></p></div></div><div class="section" id="controlling-transactions"><h2><span class="yiyi-st" id="yiyi-361">12.6.6. </span><span class="yiyi-st" id="yiyi-362">Controlling Transactions</span></h2><p><span class="yiyi-st" id="yiyi-363">默认情况下，<a class="reference internal" href="#module-sqlite3" title="sqlite3: A DB-API 2.0 implementation using SQLite 3.x."><code class="xref py py-mod docutils literal"><span class="pre">sqlite3</span></code></a>模块在数据修改语言（DML）语句之前隐式打开事务。</span><span class="yiyi-st" id="yiyi-364"><code class="docutils literal"><span class="pre">(DML:INSERT</span></code> / <code class="docutils literal"><span class="pre">UPDATE</span></code> / <code class="docutils literal"><span class="pre">DELETE</span></code> / <code class="docutils literal"><span class="pre">REPLACE</span></code>）（即除<code class="docutils literal"><span class="pre">SELECT</span></code>之外的任何东西或上述内容）。</span></p><p><span class="yiyi-st" id="yiyi-365">所以如果在事务中发出<code class="docutils literal"><span class="pre">CREATE</span> <span class="pre">TABLE</span> <span class="pre">...</span></code>、<code class="docutils literal"><span class="pre">VACUUM</span></code>、<code class="docutils literal"><span class="pre">PRAGMA</span></code>这样的命令， <a class="reference internal" href="#module-sqlite3" title="sqlite3: A DB-API 2.0 implementation using SQLite 3.x."><code class="xref py py-mod docutils literal"><span class="pre">sqlite3</span></code></a>模块将在执行这些命令之前隐式提交事务。</span><span class="yiyi-st" id="yiyi-366">这样做有两个理由。</span><span class="yiyi-st" id="yiyi-367">首先这些命令在事务中不起作用。</span><span class="yiyi-st" id="yiyi-368">另一个原因就是sqlite3需要跟踪事务状态（激活还是非激活）。</span><span class="yiyi-st" id="yiyi-369">当前事务状态通过连接对象的<a class="reference internal" href="#sqlite3.Connection.in_transaction" title="sqlite3.Connection.in_transaction"><code class="xref py py-attr docutils literal"><span class="pre">Connection.in_transaction</span></code></a>属性显示。</span></p><p><span class="yiyi-st" id="yiyi-370">通过<a class="reference internal" href="#sqlite3.connect" title="sqlite3.connect"><code class="xref py py-func docutils literal"><span class="pre">connect()</span></code></a>调用的<em>isolation_level</em>参数或者连接的<code class="xref py py-attr docutils literal"><span class="pre">isolation_level</span></code>属性，可以控制sqlite3隐式的执行哪种<code class="docutils literal"><span class="pre">BEGIN</span></code>语句（或者完全不执行）。</span></p><p><span class="yiyi-st" id="yiyi-371">如果需要<strong>自动提交模式／autocommint mode</strong>，将<code class="xref py py-attr docutils literal"><span class="pre">isolation_level</span></code>设置为None。</span></p><p><span class="yiyi-st" id="yiyi-372">其他情况下，保留其默认值，这将产生一个简单的"BEGIN"语句；或者将其设置成SQLite支持的隔离级别：“DEFERRED”、“IMMEDIATE”、或者“EXCLUSIVE”。</span></p></div><div class="section" id="using-sqlite3-efficiently"><h2><span class="yiyi-st" id="yiyi-373">12.6.7. </span><span class="yiyi-st" id="yiyi-374">Using <a class="reference internal" href="#module-sqlite3" title="sqlite3: A DB-API 2.0 implementation using SQLite 3.x."><code class="xref py py-mod docutils literal"><span class="pre">sqlite3</span></code></a> efficiently</span></h2><div class="section" id="using-shortcut-methods"><h3><span class="yiyi-st" id="yiyi-375">12.6.7.1. </span><span class="yiyi-st" id="yiyi-376">Using shortcut methods</span></h3><p><span class="yiyi-st" id="yiyi-377">使用<a class="reference internal" href="#sqlite3.Connection" title="sqlite3.Connection"><code class="xref py py-class docutils literal"><span class="pre">Connection</span></code></a>对象的非标准的<code class="xref py py-meth docutils literal"><span class="pre">executescript()</span></code>、 <code class="xref py py-meth docutils literal"><span class="pre">execute()</span></code>和<code class="xref py py-meth docutils literal"><span class="pre">executemany()</span></code>方法，代码会更简洁，因为不用显式的创建<a class="reference internal" href="#sqlite3.Cursor" title="sqlite3.Cursor"><code class="xref py py-class docutils literal"><span class="pre">Cursor</span></code></a>对象（一般不必要）。</span><span class="yiyi-st" id="yiyi-378">这些快捷方法会隐式创建并返回<a class="reference internal" href="#sqlite3.Cursor" title="sqlite3.Cursor"><code class="xref py py-class docutils literal"><span class="pre">Cursor</span></code></a>对象。</span><span class="yiyi-st" id="yiyi-379">这样，可以直接在<a class="reference internal" href="#sqlite3.Connection" title="sqlite3.Connection"><code class="xref py py-class docutils literal"><span class="pre">Connection</span></code></a>对象上只通过一个调用就可以执行<code class="docutils literal"><span class="pre">SELECT</span></code>语句并遍历结果。</span></p><pre><code class="language-python"><span></span><span class="kn">import</span> <span class="nn">sqlite3</span>
<span class="n">persons</span> <span class="o">=</span> <span class="p">[</span>
<span class="p">(</span><span class="s2">"Hugo"</span><span class="p">,</span> <span class="s2">"Boss"</span><span class="p">),</span>
<span class="p">(</span><span class="s2">"Calvin"</span><span class="p">,</span> <span class="s2">"Klein"</span><span class="p">)</span>
<span class="p">]</span>
<span class="n">con</span> <span class="o">=</span> <span class="n">sqlite3</span><span class="o">.</span><span class="n">connect</span><span class="p">(</span><span class="s2">":memory:"</span><span class="p">)</span>
<span class="c1"># Create the table</span>
<span class="n">con</span><span class="o">.</span><span class="n">execute</span><span class="p">(</span><span class="s2">"create table person(firstname, lastname)"</span><span class="p">)</span>
<span class="c1"># Fill the table</span>
<span class="n">con</span><span class="o">.</span><span class="n">executemany</span><span class="p">(</span><span class="s2">"insert into person(firstname, lastname) values (?, ?)"</span><span class="p">,</span> <span class="n">persons</span><span class="p">)</span>
<span class="c1"># Print the table contents</span>
<span class="k">for</span> <span class="n">row</span> <span class="ow">in</span> <span class="n">con</span><span class="o">.</span><span class="n">execute</span><span class="p">(</span><span class="s2">"select firstname, lastname from person"</span><span class="p">):</span>
<span class="nb">print</span><span class="p">(</span><span class="n">row</span><span class="p">)</span>
<span class="nb">print</span><span class="p">(</span><span class="s2">"I just deleted"</span><span class="p">,</span> <span class="n">con</span><span class="o">.</span><span class="n">execute</span><span class="p">(</span><span class="s2">"delete from person"</span><span class="p">)</span><span class="o">.</span><span class="n">rowcount</span><span class="p">,</span> <span class="s2">"rows"</span><span class="p">)</span>
</code></pre></div><div class="section" id="accessing-columns-by-name-instead-of-by-index"><h3><span class="yiyi-st" id="yiyi-380">12.6.7.2. </span><span class="yiyi-st" id="yiyi-381">Accessing columns by name instead of by index</span></h3><p><span class="yiyi-st" id="yiyi-382"><a class="reference internal" href="#module-sqlite3" title="sqlite3: A DB-API 2.0 implementation using SQLite 3.x."><code class="xref py py-mod docutils literal"><span class="pre">sqlite3</span></code></a>模块的一个有用功能是内部<a class="reference internal" href="#sqlite3.Row" title="sqlite3.Row"><code class="xref py py-class docutils literal"><span class="pre">sqlite3.Row</span></code></a>类，设计用作行工厂。</span></p><p><span class="yiyi-st" id="yiyi-383">由此类包装过的行可以按索引来访问（像元组），也可以按大小写无关的名字来访问。</span></p><pre><code class="language-python"><span></span><span class="kn">import</span> <span class="nn">sqlite3</span>
<span class="n">con</span> <span class="o">=</span> <span class="n">sqlite3</span><span class="o">.</span><span class="n">connect</span><span class="p">(</span><span class="s2">":memory:"</span><span class="p">)</span>
<span class="n">con</span><span class="o">.</span><span class="n">row_factory</span> <span class="o">=</span> <span class="n">sqlite3</span><span class="o">.</span><span class="n">Row</span>
<span class="n">cur</span> <span class="o">=</span> <span class="n">con</span><span class="o">.</span><span class="n">cursor</span><span class="p">()</span>
<span class="n">cur</span><span class="o">.</span><span class="n">execute</span><span class="p">(</span><span class="s2">"select 'John' as name, 42 as age"</span><span class="p">)</span>
<span class="k">for</span> <span class="n">row</span> <span class="ow">in</span> <span class="n">cur</span><span class="p">:</span>
<span class="k">assert</span> <span class="n">row</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span> <span class="o">==</span> <span class="n">row</span><span class="p">[</span><span class="s2">"name"</span><span class="p">]</span>
<span class="k">assert</span> <span class="n">row</span><span class="p">[</span><span class="s2">"name"</span><span class="p">]</span> <span class="o">==</span> <span class="n">row</span><span class="p">[</span><span class="s2">"nAmE"</span><span class="p">]</span>
<span class="k">assert</span> <span class="n">row</span><span class="p">[</span><span class="mi">1</span><span class="p">]</span> <span class="o">==</span> <span class="n">row</span><span class="p">[</span><span class="s2">"age"</span><span class="p">]</span>
<span class="k">assert</span> <span class="n">row</span><span class="p">[</span><span class="mi">1</span><span class="p">]</span> <span class="o">==</span> <span class="n">row</span><span class="p">[</span><span class="s2">"AgE"</span><span class="p">]</span>
</code></pre></div><div class="section" id="using-the-connection-as-a-context-manager"><h3><span class="yiyi-st" id="yiyi-384">12.6.7.3. </span><span class="yiyi-st" id="yiyi-385">Using the connection as a context manager</span></h3><p><span class="yiyi-st" id="yiyi-386">连接对象可以用作上下文管理器来自动提交或回滚事务。</span><span class="yiyi-st" id="yiyi-387">在异常的情况下，事务被回滚；否则，事务被提交：</span></p><pre><code class="language-python"><span></span><span class="kn">import</span> <span class="nn">sqlite3</span>
<span class="n">con</span> <span class="o">=</span> <span class="n">sqlite3</span><span class="o">.</span><span class="n">connect</span><span class="p">(</span><span class="s2">":memory:"</span><span class="p">)</span>
<span class="n">con</span><span class="o">.</span><span class="n">execute</span><span class="p">(</span><span class="s2">"create table person (id integer primary key, firstname varchar unique)"</span><span class="p">)</span>
<span class="c1"># Successful, con.commit() is called automatically afterwards</span>
<span class="k">with</span> <span class="n">con</span><span class="p">:</span>
<span class="n">con</span><span class="o">.</span><span class="n">execute</span><span class="p">(</span><span class="s2">"insert into person(firstname) values (?)"</span><span class="p">,</span> <span class="p">(</span><span class="s2">"Joe"</span><span class="p">,))</span>
<span class="c1"># con.rollback() is called after the with block finishes with an exception, the</span>
<span class="c1"># exception is still raised and must be caught</span>
<span class="k">try</span><span class="p">:</span>
<span class="k">with</span> <span class="n">con</span><span class="p">:</span>
<span class="n">con</span><span class="o">.</span><span class="n">execute</span><span class="p">(</span><span class="s2">"insert into person(firstname) values (?)"</span><span class="p">,</span> <span class="p">(</span><span class="s2">"Joe"</span><span class="p">,))</span>
<span class="k">except</span> <span class="n">sqlite3</span><span class="o">.</span><span class="n">IntegrityError</span><span class="p">:</span>
<span class="nb">print</span><span class="p">(</span><span class="s2">"couldn't add Joe twice"</span><span class="p">)</span>
</code></pre></div></div><div class="section" id="common-issues"><h2><span class="yiyi-st" id="yiyi-388">12.6.8. </span><span class="yiyi-st" id="yiyi-389">Common issues</span></h2><div class="section" id="multithreading"><h3><span class="yiyi-st" id="yiyi-390">12.6.8.1. </span><span class="yiyi-st" id="yiyi-391">Multithreading</span></h3><p><span class="yiyi-st" id="yiyi-392">老版SQLite线程间共享连接时有问题。</span><span class="yiyi-st" id="yiyi-393">这就是为什么 Python 模块不允许线程间共享连接和游标。</span><span class="yiyi-st" id="yiyi-394">如果你仍然试图这样做，则会在运行时异常。</span></p><p><span class="yiyi-st" id="yiyi-395">唯一的例外就是调用<a class="reference internal" href="#sqlite3.Connection.interrupt" title="sqlite3.Connection.interrupt"><code class="xref py py-meth docutils literal"><span class="pre">interrupt()</span></code></a>方法，它只在从不同线程中调用时有意义。</span></p><p class="rubric"><span class="yiyi-st" id="yiyi-396">脚注</span></p><table class="docutils footnote" frame="void" id="f1" rules="none"><tbody valign="top"><tr><td class="label"><span class="yiyi-st" id="yiyi-397">[1]</span></td><td><span class="yiyi-st" id="yiyi-398"><em>（<a class="fn-backref" href="#id1">1</a>，<a class="fn-backref" href="#id2">2</a>）</em>默认情况下，sqlite3模块不支持可加载扩展，因为一些平台（特别是Mac OS X）没有此功能的库。</span><span class="yiyi-st" id="yiyi-399">要获得可加载的扩展支持，必须传递-enable-loadable-sqlite-extensions以进行配置。</span></td></tr></tbody></table></div></div></div></div>
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