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:
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.
New in version 2.5: The module_globals parameter was added.
>>> import linecache >>> linecache.getline('/etc/passwd', 4) 'sys:x:3:3:sys:/dev:/bin/sh\n'