/Doc/library/linecache.rst

 1
 2:mod:`linecache` --- Random access to text lines
 3================================================
 4
 5.. module:: linecache
 6   :synopsis: This module provides random access to individual lines from text files.
 7.. sectionauthor:: Moshe Zadka <moshez@zadka.site.co.il>
 8
 9
10The :mod:`linecache` module allows one to get any line from any file, while
11attempting to optimize internally, using a cache, the common case where many
12lines are read from a single file.  This is used by the :mod:`traceback` module
13to retrieve source lines for inclusion in  the formatted traceback.
14
15The :mod:`linecache` module defines the following functions:
16
17
18.. function:: getline(filename, lineno[, module_globals])
19
20   Get line *lineno* from file named *filename*. This function will never throw an
21   exception --- it will return ``''`` on errors (the terminating newline character
22   will be included for lines that are found).
23
24   .. index:: triple: module; search; path
25
26   If a file named *filename* is not found, the function will look for it in the
27   module search path, ``sys.path``, after first checking for a :pep:`302`
28   ``__loader__`` in *module_globals*, in case the module was imported from a
29   zipfile or other non-filesystem import source.
30
31   .. versionadded:: 2.5
32      The *module_globals* parameter was added.
33
34
35.. function:: clearcache()
36
37   Clear the cache.  Use this function if you no longer need lines from files
38   previously read using :func:`getline`.
39
40
41.. function:: checkcache([filename])
42
43   Check the cache for validity.  Use this function if files in the cache  may have
44   changed on disk, and you require the updated version.  If *filename* is omitted,
45   it will check all the entries in the cache.
46
47Example::
48
49   >>> import linecache
50   >>> linecache.getline('/etc/passwd', 4)
51   'sys:x:3:3:sys:/dev:/bin/sh\n'
52