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<H2>
<BR>
7.11.1 Database Objects
</H2>
<P>
The database objects returned by <tt class="function">open()</tt> provide the methods
common to all the DBM-style databases. The following methods are
available in addition to the standard methods.
<P>
<dl><dt><b><a name='l2h-1718'><tt class='method'>first</tt></a></b> ()
<dd>
It's possible to loop over every key in the database using this method
and the <tt class="method">next()</tt> method. The traversal is ordered by
the databases internal hash values, and won't be sorted by the key
values. This method returns the starting key.
</dl>
<P>
<dl><dt><b><a name='l2h-1719'><tt class='method'>last</tt></a></b> ()
<dd>
Return the last key in a database traversal. This may be used to
begin a reverse-order traversal; see <tt class="method">previous()</tt>.
</dl>
<P>
<dl><dt><b><a name='l2h-1720'><tt class='method'>next</tt></a></b> (<var>key</var>)
<dd>
Returns the key that follows <var>key</var> in the traversal. The
following code prints every key in the database <code>db</code>, without
having to create a list in memory that contains them all:
<P>
<dl><dd><pre class="verbatim">
k = db.first()
while k != None:
print k
k = db.next(k)
</pre></dl>
</dl>
<P>
<dl><dt><b><a name='l2h-1721'><tt class='method'>previous</tt></a></b> (<var>key</var>)
<dd>
Return the key that comes before <var>key</var> in a forward-traversal of
the database. In conjunction with <tt class="method">last()</tt>, this may be used
to implement a reverse-order traversal.
</dl>
<P>
<dl><dt><b><a name='l2h-1722'><tt class='method'>sync</tt></a></b> ()
<dd>
This method forces any unwritten data to be written to the disk.
</dl>
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