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<H1><A NAME="SECTION0010600000000000000000">
8.6 <tt class="module">dbm</tt> --
Simple ``database'' interface</A>
</H1>
<P>
<p class='availability'>Availability: <span
class='platform'>Unix</span>.</p>
<P>
The <tt class="module">dbm</tt> module provides an interface to the Unix
(<code>n</code>)<code>dbm</code> 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
<tt class="method">items()</tt> and <tt class="method">values()</tt> methods are not supported.
<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 <b class="program">configure</b> script will attempt to locate the
appropriate header file to simplify building this module.
<P>
The module defines the following:
<P>
<dl><dt><b><a name='l2h-1837'><tt class='exception'>error</tt></a></b>
<dd>
Raised on dbm-specific errors, such as I/O errors.
<tt class="exception">KeyError</tt> is raised for general mapping errors like
specifying an incorrect key.
</dl>
<P>
<dl><dt><b><a name='l2h-1838'><tt>library</tt></a></b>
<dd>
Name of the <code>ndbm</code> implementation library used.
</dl>
<P>
<dl><dt><b><a name='l2h-1839'><tt class='function'>open</tt></a></b> (<var>filename</var><big>[</big><var>, flag</var><big>[</big><var>, mode</var><big>]</big><big>]</big>)
<dd>
Open a dbm database and return a dbm object. The <var>filename</var>
argument is the name of the database file (without the <span class="file">.dir</span> or
<span class="file">.pag</span> extensions; note that the BSD DB implementation of the
interface will append the extension <span class="file">.db</span> and only create one
file).
<P>
The optional <var>flag</var> argument must be one of these values:
<P>
<table border align="center" style="border-collapse: collapse">
<thead>
<tr class="tableheader">
<th align="center"><b>Value</b> </th>
<th align="left"><b>Meaning</b> </th>
</thead>
<tbody valign='baseline'>
<tr><td align="center" valign="baseline"><code>'r'</code></td>
<td align="left">Open existing database for reading only (default)</td>
<tr><td align="center" valign="baseline"><code>'w'</code></td>
<td align="left">Open existing database for reading and writing</td>
<tr><td align="center" valign="baseline"><code>'c'</code></td>
<td align="left">Open database for reading and writing, creating it if
it doesn't exist</td>
<tr><td align="center" valign="baseline"><code>'n'</code></td>
<td align="left">Always create a new, empty database, open for reading
and writing</td></tbody>
</table>
<P>
The optional <var>mode</var> argument is the Unix mode of the file, used
only when the database has to be created. It defaults to octal
<code>0666</code>.
</dl>
<P>
<div class='seealso'>
<p class='heading'><b>See Also:</b></p>
<dl compact class="seemodule">
<dt>Module <b><tt class='module'><a href="module-anydbm.html" tppabs="http://www.python.org/doc/current/lib/module-anydbm.html">anydbm</a></tt>:</b>
<dd>Generic interface to <code>dbm</code>-style databases.
</dl>
<dl compact class="seemodule">
<dt>Module <b><tt class='module'><a href="module-gdbm.html" tppabs="http://www.python.org/doc/current/lib/module-gdbm.html">gdbm</a></tt>:</b>
<dd>Similar interface to the GNU GDBM library.
</dl>
<dl compact class="seemodule">
<dt>Module <b><tt class='module'><a href="module-whichdb.html" tppabs="http://www.python.org/doc/current/lib/module-whichdb.html">whichdb</a></tt>:</b>
<dd>Utility module used to determine the type of an
existing database.
</dl>
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