:mod:`linecache` --- Random access to text lines ================================================ .. module:: linecache :synopsis: Provides random access to individual lines from text files. .. sectionauthor:: Moshe Zadka <moshez@zadka.site.co.il> **Source code:** :source:`Lib/linecache.py` -------------- The :mod:`linecache` module allows one to get any line from a Python source 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 :mod:`traceback` module to retrieve source lines for inclusion in the formatted traceback. The :func:`tokenize.open` function is used to open files. This function uses :func:`tokenize.detect_encoding` to get the encoding of the file; in the absence of an encoding token, the file encoding defaults to UTF-8. The :mod:`linecache` module defines the following functions: .. function:: getline(filename, lineno, module_globals=None) Get line *lineno* from file named *filename*. This function will never raise an exception --- it will return ``''`` on errors (the terminating newline character will be included for lines that are found). .. index:: triple: module; search; path If a file named *filename* is not found, the function first checks for a :pep:`302` ``__loader__`` in *module_globals*. If there is such a loader and it defines a ``get_source`` method, then that determines the source lines (if ``get_source()`` returns ``None``, then ``''`` is returned). Finally, if *filename* is a relative filename, it is looked up relative to the entries in the module search path, ``sys.path``. .. function:: clearcache() Clear the cache. Use this function if you no longer need lines from files previously read using :func:`getline`. .. function:: 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. .. function:: lazycache(filename, module_globals) Capture enough detail about a non-file-based module to permit getting its lines later via :func:`getline` even if *module_globals* is ``None`` in the later call. This avoids doing I/O until a line is actually needed, without having to carry the module globals around indefinitely. .. versionadded:: 3.5 Example:: >>> import linecache >>> linecache.getline(linecache.__file__, 8) 'import sys\n'
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