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