
``linecache`` --- Random access to text lines
*********************************************

The ``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 ``traceback`` module to retrieve source lines for inclusion in
the formatted traceback.

The ``linecache`` module defines the following functions:

linecache.getline(filename, lineno, module_globals=None)

   Get line *lineno* from file named *filename*. This function will
   never throw an exception --- it will return ``''`` on errors (the
   terminating newline character will be included for lines that are
   found).

   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.

linecache.clearcache()

   Clear the cache.  Use this function if you no longer need lines
   from files previously read using ``getline()``.

linecache.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'
