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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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	54
	55	<H1><A NAME="SECTION0051300000000000000000">
	56	3.13 <tt class="module">linecache</tt> --
	57	Random access to text lines</A>
	58	</H1>
	59
	60	<P>
	61	<A NAME="module-linecache"></A>
	62
	63	<P>
	64	The <tt class="module">linecache</tt> module allows one to get any line from any file,
65	while attempting to optimize internally, using a cache, the common case
66	where many lines are read from a single file. This is used by the
67	<tt class="module"><a href="module-traceback.html">traceback</a></tt> module to retrieve source lines for inclusion in
68	the formatted traceback.
69
70	<P>
71	The <tt class="module">linecache</tt> module defines the following functions:
72
73	<P>
74	<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
75	<td><nobr><b><tt id='l2h-621' xml:id='l2h-621' class="function">getline</tt></b>(</nobr></td>
76	<td><var>filename, lineno</var>)</td></tr></table></dt>
77	<dd>
78	Get line <var>lineno</var> from file named <var>filename</var>. This function
79	will never throw an exception -- it will return <code>''</code> on errors
80	(the terminating newline character will be included for lines that are
81	found).
82
83	<P>
84	If a file named <var>filename</var> is not found, the function will look
85	for it in the module<a id='l2h-622' xml:id='l2h-622'></a> search path,
86	<code>sys.path</code>.
87	</dl>
88
89	<P>
90	<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
91	<td><nobr><b><tt id='l2h-623' xml:id='l2h-623' class="function">clearcache</tt></b>(</nobr></td>
92	<td><var></var>)</td></tr></table></dt>
93	<dd>
94	Clear the cache. Use this function if you no longer need lines from
95	files previously read using <tt class="function">getline()</tt>.
96	</dl>
97
98	<P>
99	<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
100	<td><nobr><b><tt id='l2h-624' xml:id='l2h-624' class="function">checkcache</tt></b>(</nobr></td>
101	<td><var></var><big>[</big><var>filename</var><big>]</big><var></var>)</td></tr></table></dt>
102	<dd>
103	Check the cache for validity. Use this function if files in the cache
104	may have changed on disk, and you require the updated version. If
105	<var>filename</var> is omitted, it will check the whole cache entries.
106	</dl>
107
108	<P>
109	Example:
110
111	<P>
112	<div class="verbatim"><pre>
113	>>> import linecache
114	>>> linecache.getline('/etc/passwd', 4)
115	'sys:x:3:3:sys:/dev:/bin/sh\n'
116	</pre></div>
117
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