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:mod:`linecache` --- Random access to text lines
================================================
.. module:: linecache
:synopsis: This module provides random access to individual lines from text files.
.. sectionauthor:: Moshe Zadka <moshez@zadka.site.co.il>
**Source code:** :source:`Lib/linecache.py`
--------------
The :mod:`linecache` 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 :mod:`traceback` module
to retrieve source lines for inclusion in the formatted traceback.
The :mod:`linecache` module defines the following functions:
.. function:: getline(filename, lineno, module_globals=None)
Get line *lineno* from file named *filename*. This function will never raise an
exception --- it will return ``''`` on errors (the terminating newline character
will be included for lines that are found).
.. index:: triple: module; search; path
If a file named *filename* is not found, the function will look for it in the
module search path, ``sys.path``, after first checking for a :pep:`302`
``__loader__`` in *module_globals*, in case the module was imported from a
zipfile or other non-filesystem import source.
.. function:: clearcache()
Clear the cache. Use this function if you no longer need lines from files
previously read using :func:`getline`.
.. function:: checkcache(filename=None)
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 *filename* is omitted,
it will check all the entries in the cache.
Example::
>>> import linecache
>>> linecache.getline('/etc/passwd', 4)
'sys:x:3:3:sys:/dev:/bin/sh\n'
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