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<title>3.13 linecache -- Random access to text lines</title>
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<H1><A NAME="SECTION0051300000000000000000">
3.13 <tt class="module">linecache</tt> --
         Random access to text lines</A>
</H1>

<P>
<A NAME="module-linecache"></A>

<P>
The <tt class="module">linecache</tt> module allows one to get any line from any file,
while attempting to optimize internally, using a cache, the common case
where many lines are read from a single file.  This is used by the
<tt class="module"><a href="module-traceback.html">traceback</a></tt> module to retrieve source lines for inclusion in
the formatted traceback.

<P>
The <tt class="module">linecache</tt> module defines the following functions:

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-621' xml:id='l2h-621' class="function">getline</tt></b>(</nobr></td>
  <td><var>filename, lineno</var>)</td></tr></table></dt>
<dd>
Get line <var>lineno</var> from file named <var>filename</var>. This function
will never throw an exception -- it will return <code>''</code> on errors
(the terminating newline character will be included for lines that are
found).

<P>
If a file named <var>filename</var> is not found, the function will look
for it in the module<a id='l2h-622' xml:id='l2h-622'></a> search path,
<code>sys.path</code>.
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-623' xml:id='l2h-623' class="function">clearcache</tt></b>(</nobr></td>
  <td><var></var>)</td></tr></table></dt>
<dd>
Clear the cache.  Use this function if you no longer need lines from
files previously read using <tt class="function">getline()</tt>.
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-624' xml:id='l2h-624' class="function">checkcache</tt></b>(</nobr></td>
  <td><var></var><big>[</big><var>filename</var><big>]</big><var></var>)</td></tr></table></dt>
<dd>
Check the cache for validity.  Use this function if files in the cache
may have changed on disk, and you require the updated version.  If
<var>filename</var> is omitted, it will check the whole cache entries.
</dl>

<P>
Example:

<P>
<div class="verbatim"><pre>
&gt;&gt;&gt; import linecache
&gt;&gt;&gt; linecache.getline('/etc/passwd', 4)
'sys:x:3:3:sys:/dev:/bin/sh\n'
</pre></div>

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<span class="release-info">Release 2.4.2, documentation updated on 28 September 2005.</span>
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