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<H2><A NAME="SECTION009910000000000000000"></A>
<BR>
7.9.1 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-1401"><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-1402"><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-1403"><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 <tt>db</tt>, 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-1404"><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-1405"><tt class=method>sync</tt></a></b> ()
<dd>
  This method forces any unwritten data to be written to the disk.
</dl><p>
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