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