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Data Persistence</a> »</li> </ul> </div> <div class="document"> <div class="documentwrapper"> <div class="bodywrapper"> <div class="body"> <div class="section" id="module-anydbm"> <span id="anydbm-generic-access-to-dbm-style-databases"></span><h1>11.6. <a class="reference internal" href="#module-anydbm" title="anydbm: Generic interface to DBM-style database modules."><tt class="xref py py-mod docutils literal"><span class="pre">anydbm</span></tt></a> — Generic access to DBM-style databases<a class="headerlink" href="#module-anydbm" title="Permalink to this headline">¶</a></h1> <div class="admonition note"> <p class="first admonition-title">Note</p> <p class="last">The <a class="reference internal" href="#module-anydbm" title="anydbm: Generic interface to DBM-style database modules."><tt class="xref py py-mod docutils literal"><span class="pre">anydbm</span></tt></a> module has been renamed to <a class="reference internal" href="dbm.html#module-dbm" title="dbm: The standard "database" interface, based on ndbm. (Unix)"><tt class="xref py py-mod docutils literal"><span class="pre">dbm</span></tt></a> in Python 3. The <a class="reference internal" href="../glossary.html#term-to3"><em class="xref std std-term">2to3</em></a> tool will automatically adapt imports when converting your sources to Python 3.</p> </div> <p id="index-0"><a class="reference internal" href="#module-anydbm" title="anydbm: Generic interface to DBM-style database modules."><tt class="xref py py-mod docutils literal"><span class="pre">anydbm</span></tt></a> is a generic interface to variants of the DBM database — <a class="reference internal" href="dbhash.html#module-dbhash" title="dbhash: DBM-style interface to the BSD database library."><tt class="xref py py-mod docutils literal"><span class="pre">dbhash</span></tt></a> (requires <a class="reference internal" href="bsddb.html#module-bsddb" title="bsddb: Interface to Berkeley DB database library"><tt class="xref py py-mod docutils literal"><span class="pre">bsddb</span></tt></a>), <a class="reference internal" href="gdbm.html#module-gdbm" title="gdbm: GNU's reinterpretation of dbm. (Unix)"><tt class="xref py py-mod docutils literal"><span class="pre">gdbm</span></tt></a>, or <a class="reference internal" href="dbm.html#module-dbm" title="dbm: The standard "database" interface, based on ndbm. (Unix)"><tt class="xref py py-mod docutils literal"><span class="pre">dbm</span></tt></a>. If none of these modules is installed, the slow-but-simple implementation in module <a class="reference internal" href="dumbdbm.html#module-dumbdbm" title="dumbdbm: Portable implementation of the simple DBM interface."><tt class="xref py py-mod docutils literal"><span class="pre">dumbdbm</span></tt></a> will be used.</p> <dl class="function"> <dt id="anydbm.open"> <tt class="descclassname">anydbm.</tt><tt class="descname">open</tt><big>(</big><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><big>)</big><a class="headerlink" href="#anydbm.open" title="Permalink to this definition">¶</a></dt> <dd><p>Open the database file <em>filename</em> and return a corresponding object.</p> <p>If the database file already exists, the <a class="reference internal" href="whichdb.html#module-whichdb" title="whichdb: Guess which DBM-style module created a given database."><tt class="xref py py-mod docutils literal"><span class="pre">whichdb</span></tt></a> module is used to determine its type and the appropriate module is used; if it does not exist, the first module listed above that can be imported is used.</p> <p>The optional <em>flag</em> argument must be one of these values:</p> <table border="1" class="docutils"> <colgroup> <col width="17%" /> <col width="83%" /> </colgroup> <thead valign="bottom"> <tr class="row-odd"><th class="head">Value</th> <th class="head">Meaning</th> </tr> </thead> <tbody valign="top"> <tr class="row-even"><td><tt class="docutils literal"><span class="pre">'r'</span></tt></td> <td>Open existing database for reading only (default)</td> </tr> <tr class="row-odd"><td><tt class="docutils literal"><span class="pre">'w'</span></tt></td> <td>Open existing database for reading and writing</td> </tr> <tr class="row-even"><td><tt class="docutils literal"><span class="pre">'c'</span></tt></td> <td>Open database for reading and writing, creating it if it doesn’t exist</td> </tr> <tr class="row-odd"><td><tt class="docutils literal"><span class="pre">'n'</span></tt></td> <td>Always create a new, empty database, open for reading and writing</td> </tr> </tbody> </table> <p>If not specified, the default value is <tt class="docutils literal"><span class="pre">'r'</span></tt>.</p> <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 <tt class="docutils literal"><span class="pre">0666</span></tt> (and will be modified by the prevailing umask).</p> </dd></dl> <dl class="exception"> <dt id="anydbm.error"> <em class="property">exception </em><tt class="descclassname">anydbm.</tt><tt class="descname">error</tt><a class="headerlink" href="#anydbm.error" title="Permalink to this definition">¶</a></dt> <dd><p>A tuple containing the exceptions that can be raised by each of the supported modules, with a unique exception also named <a class="reference internal" href="#anydbm.error" title="anydbm.error"><tt class="xref py py-exc docutils literal"><span class="pre">anydbm.error</span></tt></a> as the first item — the latter is used when <a class="reference internal" href="#anydbm.error" title="anydbm.error"><tt class="xref py py-exc docutils literal"><span class="pre">anydbm.error</span></tt></a> is raised.</p> </dd></dl> <p>The object returned by <a class="reference internal" href="#anydbm.open" title="anydbm.open"><tt class="xref py py-func docutils literal"><span class="pre">open()</span></tt></a> supports most of the same functionality as dictionaries; keys and their corresponding values can be stored, retrieved, and deleted, and the <tt class="xref py py-meth docutils literal"><span class="pre">has_key()</span></tt> and <tt class="xref py py-meth docutils literal"><span class="pre">keys()</span></tt> methods are available. Keys and values must always be strings.</p> <p>The following example records some hostnames and a corresponding title, and then prints out the contents of the database:</p> <div class="highlight-python"><div class="highlight"><pre><span class="kn">import</span> <span class="nn">anydbm</span> <span class="c"># Open database, creating it if necessary.</span> <span class="n">db</span> <span class="o">=</span> <span class="n">anydbm</span><span class="o">.</span><span class="n">open</span><span class="p">(</span><span class="s">'cache'</span><span class="p">,</span> <span class="s">'c'</span><span class="p">)</span> <span class="c"># Record some values</span> <span class="n">db</span><span class="p">[</span><span class="s">'www.python.org'</span><span class="p">]</span> <span class="o">=</span> <span class="s">'Python Website'</span> <span class="n">db</span><span class="p">[</span><span class="s">'www.cnn.com'</span><span class="p">]</span> <span class="o">=</span> <span class="s">'Cable News Network'</span> <span class="c"># Loop through contents. Other dictionary methods</span> <span class="c"># such as .keys(), .values() also work.</span> <span class="k">for</span> <span class="n">k</span><span class="p">,</span> <span class="n">v</span> <span class="ow">in</span> <span class="n">db</span><span class="o">.</span><span class="n">iteritems</span><span class="p">():</span> <span class="k">print</span> <span class="n">k</span><span class="p">,</span> <span class="s">'</span><span class="se">\t</span><span class="s">'</span><span class="p">,</span> <span class="n">v</span> <span class="c"># Storing a non-string key or value will raise an exception (most</span> <span class="c"># likely a TypeError).</span> <span class="n">db</span><span class="p">[</span><span class="s">'www.yahoo.com'</span><span class="p">]</span> <span class="o">=</span> <span class="mi">4</span> <span class="c"># Close when done.</span> <span class="n">db</span><span class="o">.</span><span class="n">close</span><span class="p">()</span> </pre></div> </div> <div class="admonition-see-also admonition seealso"> <p class="first admonition-title">See also</p> <dl class="last docutils"> <dt>Module <a class="reference internal" href="dbhash.html#module-dbhash" title="dbhash: DBM-style interface to the BSD database library."><tt class="xref py py-mod docutils literal"><span class="pre">dbhash</span></tt></a></dt> <dd>BSD <tt class="docutils literal"><span class="pre">db</span></tt> database interface.</dd> <dt>Module <a class="reference internal" href="dbm.html#module-dbm" title="dbm: The standard "database" interface, based on ndbm. (Unix)"><tt class="xref py py-mod docutils literal"><span class="pre">dbm</span></tt></a></dt> <dd>Standard Unix database interface.</dd> <dt>Module <a class="reference internal" href="dumbdbm.html#module-dumbdbm" title="dumbdbm: Portable implementation of the simple DBM interface."><tt class="xref py py-mod docutils literal"><span class="pre">dumbdbm</span></tt></a></dt> <dd>Portable implementation of the <tt class="docutils literal"><span class="pre">dbm</span></tt> interface.</dd> <dt>Module <a class="reference internal" href="gdbm.html#module-gdbm" title="gdbm: GNU's reinterpretation of dbm. (Unix)"><tt class="xref py py-mod docutils literal"><span class="pre">gdbm</span></tt></a></dt> <dd>GNU database interface, based on the <tt class="docutils literal"><span class="pre">dbm</span></tt> interface.</dd> <dt>Module <a class="reference internal" href="shelve.html#module-shelve" title="shelve: Python object persistence."><tt class="xref py py-mod docutils literal"><span class="pre">shelve</span></tt></a></dt> <dd>General object persistence built on top of the Python <tt class="docutils literal"><span class="pre">dbm</span></tt> interface.</dd> <dt>Module <a class="reference internal" href="whichdb.html#module-whichdb" title="whichdb: Guess which DBM-style module created a given database."><tt class="xref py py-mod docutils literal"><span class="pre">whichdb</span></tt></a></dt> <dd>Utility module used to determine the type of an existing database.</dd> </dl> </div> </div> </div> </div> </div> <div class="sphinxsidebar"> <div class="sphinxsidebarwrapper"> <h4>Previous topic</h4> <p class="topless"><a href="marshal.html" title="previous chapter">11.5. <tt class="docutils literal"><span class="pre">marshal</span></tt> — Internal Python object serialization</a></p> <h4>Next topic</h4> <p class="topless"><a href="whichdb.html" title="next chapter">11.7. <tt class="docutils literal"><span class="pre">whichdb</span></tt> — Guess which DBM module created a database</a></p> <h3>This Page</h3> <ul class="this-page-menu"> <li><a href="../bugs.html">Report a Bug</a></li> <li><a href="../_sources/library/anydbm.txt" rel="nofollow">Show Source</a></li> </ul> <div id="searchbox" style="display: none"> <h3>Quick search</h3> <form class="search" action="../search.html" method="get"> <input type="text" name="q" /> <input type="submit" value="Go" /> <input type="hidden" name="check_keywords" value="yes" /> <input type="hidden" name="area" value="default" /> </form> <p class="searchtip" style="font-size: 90%"> Enter search terms or a module, class or function name. </p> </div> <script type="text/javascript">$('#searchbox').show(0);</script> </div> </div> <div class="clearer"></div> </div> <div class="related"> <h3>Navigation</h3> <ul> <li class="right" style="margin-right: 10px"> <a href="../genindex.html" title="General Index" >index</a></li> <li class="right" > <a href="../py-modindex.html" title="Python Module Index" >modules</a> |</li> <li class="right" > <a href="whichdb.html" title="11.7. whichdb — Guess which DBM module created a database" >next</a> |</li> <li class="right" > <a href="marshal.html" title="11.5. marshal — Internal Python object serialization" >previous</a> |</li> <li><img src="../_static/py.png" alt="" style="vertical-align: middle; margin-top: -1px"/></li> <li><a href="http://www.python.org/">Python</a> »</li> <li> <a href="../index.html">Python 2.7.5 documentation</a> » </li> <li><a href="index.html" >The Python Standard Library</a> »</li> <li><a href="persistence.html" >11. 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