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<H2><A NAME="SECTION0091210000000000000000"> </A>
<BR>
7.12.1 Hash, BTree and Record Objects
</H2>
<P>
Once instantiated, hash, btree and record objects support the following
methods:
<P>
<dl><dt><b><a name="l2h-2035"><tt class="method">close</tt></a></b>()
<dd>
Close the underlying file. The object can no longer be accessed. Since
there is no open <tt class="method">open</tt> method for these objects, to open the file
again a new <tt class="module">bsddb</tt> module open function must be called.
</dl>
<P>
<dl><dt><b><a name="l2h-2036"><tt class="method">keys</tt></a></b>()
<dd>
Return the list of keys contained in the DB file. The order of the list is
unspecified and should not be relied on. In particular, the order of the
list returned is different for different file formats.
</dl>
<P>
<dl><dt><b><a name="l2h-2037"><tt class="method">has_key</tt></a></b>(<var>key</var>)
<dd>
Return <code>1</code> if the DB file contains the argument as a key.
</dl>
<P>
<dl><dt><b><a name="l2h-2038"><tt class="method">set_location</tt></a></b>(<var>key</var>)
<dd>
Set the cursor to the item indicated by <var>key</var> and return a tuple
containing the key and its value. For binary tree databases (opened
using <tt class="function">btopen()</tt>), if <var>key</var> does not actually exist in
the database, the cursor will point to the next item in sorted order
and return that key and value. For other databases,
<tt class="exception">KeyError</tt> will be raised if <var>key</var> is not found in the
database.
</dl>
<P>
<dl><dt><b><a name="l2h-2039"><tt class="method">first</tt></a></b>()
<dd>
Set the cursor to the first item in the DB file and return it. The order of
keys in the file is unspecified, except in the case of B-Tree databases.
</dl>
<P>
<dl><dt><b><a name="l2h-2040"><tt class="method">next</tt></a></b>()
<dd>
Set the cursor to the next item in the DB file and return it. The order of
keys in the file is unspecified, except in the case of B-Tree databases.
</dl>
<P>
<dl><dt><b><a name="l2h-2041"><tt class="method">previous</tt></a></b>()
<dd>
Set the cursor to the first item in the DB file and return it. The
order of keys in the file is unspecified, except in the case of B-Tree
databases. This is not supported on hashtable databases (those opened
with <tt class="function">hashopen()</tt>).
</dl>
<P>
<dl><dt><b><a name="l2h-2042"><tt class="method">last</tt></a></b>()
<dd>
Set the cursor to the last item in the DB file and return it. The
order of keys in the file is unspecified. This is not supported on
hashtable databases (those opened with <tt class="function">hashopen()</tt>).
</dl>
<P>
<dl><dt><b><a name="l2h-2043"><tt class="method">sync</tt></a></b>()
<dd>
Synchronize the database on disk.
</dl>
<P>
Example:
<P>
<dl><dd><pre class="verbatim">
>>> import bsddb
>>> db = bsddb.btopen('/tmp/spam.db', 'c')
>>> for i in range(10): db['%d'%i] = '%d'% (i*i)
...
>>> db['3']
'9'
>>> db.keys()
['0', '1', '2', '3', '4', '5', '6', '7', '8', '9']
>>> db.first()
('0', '0')
>>> db.next()
('1', '1')
>>> db.last()
('9', '81')
>>> db.set_location('2')
('2', '4')
>>> db.previous()
('1', '1')
>>> db.sync()
0
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<span class="release-info">Release 2.2, documentation updated on December 21, 2001.</span>
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