# 3.13 `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:

`getline`(filename, lineno)
  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`.

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

`checkcache`()
  Check the cache for validity. Use this function if files in the cache may have changed on disk, and you require the updated version.

Example:

      >>> import linecache
      >>> linecache.getline('/etc/passwd', 4)
      'sys:x:3:3:sys:/dev:/bin/sh\n'