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<div class="section" id="module-dbm">
<span id="dbm-simple-database-interface"></span><h1>11.8. <a class="reference internal" href="#module-dbm" title="dbm: The standard "database" interface, based on ndbm. (Unix)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">dbm</span></code></a> — Simple “database” interface<a class="headerlink" href="#module-dbm" title="Permalink to this headline">¶</a></h1>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p>The <a class="reference internal" href="#module-dbm" title="dbm: The standard "database" interface, based on ndbm. (Unix)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">dbm</span></code></a> module has been renamed to <code class="xref py py-mod docutils literal notranslate"><span class="pre">dbm.ndbm</span></code> in Python 3. The
<a class="reference internal" href="../glossary.html#term-2to3"><span class="xref std std-term">2to3</span></a> tool will automatically adapt imports when converting your
sources to Python 3.</p>
</div>
<p>The <a class="reference internal" href="#module-dbm" title="dbm: The standard "database" interface, based on ndbm. (Unix)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">dbm</span></code></a> module provides an interface to the Unix “(n)dbm” library. Dbm
objects behave like mappings (dictionaries), except that keys and values are
always strings. Printing a dbm object doesn’t print the keys and values, and the
<code class="xref py py-meth docutils literal notranslate"><span class="pre">items()</span></code> and <code class="xref py py-meth docutils literal notranslate"><span class="pre">values()</span></code> methods are not supported.</p>
<p>This module can be used with the “classic” ndbm interface, the BSD DB
compatibility interface, or the GNU GDBM compatibility interface. On Unix, the
<strong class="program">configure</strong> script will attempt to locate the appropriate header file
to simplify building this module.</p>
<p>The module defines the following:</p>
<dl class="exception">
<dt id="dbm.error">
<em class="property">exception </em><code class="descclassname">dbm.</code><code class="descname">error</code><a class="headerlink" href="#dbm.error" title="Permalink to this definition">¶</a></dt>
<dd><p>Raised on dbm-specific errors, such as I/O errors. <a class="reference internal" href="exceptions.html#exceptions.KeyError" title="exceptions.KeyError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">KeyError</span></code></a> is raised for
general mapping errors like specifying an incorrect key.</p>
</dd></dl>
<dl class="data">
<dt id="dbm.library">
<code class="descclassname">dbm.</code><code class="descname">library</code><a class="headerlink" href="#dbm.library" title="Permalink to this definition">¶</a></dt>
<dd><p>Name of the <code class="docutils literal notranslate"><span class="pre">ndbm</span></code> implementation library used.</p>
</dd></dl>
<dl class="function">
<dt id="dbm.open">
<code class="descclassname">dbm.</code><code class="descname">open</code><span class="sig-paren">(</span><em>filename</em><span class="optional">[</span>, <em>flag</em><span class="optional">[</span>, <em>mode</em><span class="optional">]</span><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#dbm.open" title="Permalink to this definition">¶</a></dt>
<dd><p>Open a dbm database and return a dbm object. The <em>filename</em> argument is the
name of the database file (without the <code class="file docutils literal notranslate"><span class="pre">.dir</span></code> or <code class="file docutils literal notranslate"><span class="pre">.pag</span></code> extensions;
note that the BSD DB implementation of the interface will append the extension
<code class="file docutils literal notranslate"><span class="pre">.db</span></code> and only create one file).</p>
<p>The optional <em>flag</em> argument must be one of these values:</p>
<table class="docutils align-center">
<colgroup>
<col style="width: 17%" />
<col style="width: 83%" />
</colgroup>
<thead>
<tr class="row-odd"><th class="head"><p>Value</p></th>
<th class="head"><p>Meaning</p></th>
</tr>
</thead>
<tbody>
<tr class="row-even"><td><p><code class="docutils literal notranslate"><span class="pre">'r'</span></code></p></td>
<td><p>Open existing database for reading only
(default)</p></td>
</tr>
<tr class="row-odd"><td><p><code class="docutils literal notranslate"><span class="pre">'w'</span></code></p></td>
<td><p>Open existing database for reading and
writing</p></td>
</tr>
<tr class="row-even"><td><p><code class="docutils literal notranslate"><span class="pre">'c'</span></code></p></td>
<td><p>Open database for reading and writing,
creating it if it doesn’t exist</p></td>
</tr>
<tr class="row-odd"><td><p><code class="docutils literal notranslate"><span class="pre">'n'</span></code></p></td>
<td><p>Always create a new, empty database, open
for reading and writing</p></td>
</tr>
</tbody>
</table>
<p>The optional <em>mode</em> argument is the Unix mode of the file, used only when the
database has to be created. It defaults to octal <code class="docutils literal notranslate"><span class="pre">0666</span></code> (and will be
modified by the prevailing umask).</p>
<p>In addition to the dictionary-like methods, <code class="docutils literal notranslate"><span class="pre">dbm</span></code> objects
provide the following method:</p>
<dl class="function">
<dt id="dbm.close">
<code class="descclassname">dbm.</code><code class="descname">close</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#dbm.close" title="Permalink to this definition">¶</a></dt>
<dd><p>Close the <code class="docutils literal notranslate"><span class="pre">dbm</span></code> database.</p>
</dd></dl>
</dd></dl>
<div class="admonition seealso">
<p class="admonition-title">See also</p>
<dl class="simple">
<dt>Module <a class="reference internal" href="anydbm.html#module-anydbm" title="anydbm: Generic interface to DBM-style database modules."><code class="xref py py-mod docutils literal notranslate"><span class="pre">anydbm</span></code></a></dt><dd><p>Generic interface to <code class="docutils literal notranslate"><span class="pre">dbm</span></code>-style databases.</p>
</dd>
<dt>Module <a class="reference internal" href="gdbm.html#module-gdbm" title="gdbm: GNU's reinterpretation of dbm. (Unix)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">gdbm</span></code></a></dt><dd><p>Similar interface to the GNU GDBM library.</p>
</dd>
<dt>Module <a class="reference internal" href="whichdb.html#module-whichdb" title="whichdb: Guess which DBM-style module created a given database."><code class="xref py py-mod docutils literal notranslate"><span class="pre">whichdb</span></code></a></dt><dd><p>Utility module used to determine the type of an existing database.</p>
</dd>
</dl>
</div>
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