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:mod:`!filecmp` --- File and Directory Comparisons

.. module:: filecmp
   :synopsis: Compare files efficiently.


.. sectionauthor:: Moshe Zadka <[email protected]>

Source code: :source:`Lib/filecmp.py`

The :mod:`filecmp` module defines functions to compare files and directories, with various optional time/correctness trade-offs. For comparing files, see also the :mod:`difflib` module.

The :mod:`filecmp` module defines the following functions:

.. function:: cmp(f1, f2, shallow=True)

   Compare the files named *f1* and *f2*, returning ``True`` if they seem equal,
   ``False`` otherwise.

   If *shallow* is true and the :func:`os.stat` signatures (file type, size, and
   modification time) of both files are identical, the files are taken to be
   equal.

   Otherwise, the files are treated as different if their sizes or contents differ.

   Note that no external programs are called from this function, giving it
   portability and efficiency.

   This function uses a cache for past comparisons and the results,
   with cache entries invalidated if the :func:`os.stat` information for the
   file changes.  The entire cache may be cleared using :func:`clear_cache`.



.. function:: cmpfiles(dir1, dir2, common, shallow=True)

   Compare the files in the two directories *dir1* and *dir2* whose names are
   given by *common*.

   Returns three lists of file names: *match*, *mismatch*,
   *errors*.  *match* contains the list of files that match, *mismatch* contains
   the names of those that don't, and *errors* lists the names of files which
   could not be compared.  Files are listed in *errors* if they don't exist in
   one of the directories, the user lacks permission to read them or if the
   comparison could not be done for some other reason.

   The *shallow* parameter has the same meaning and default value as for
   :func:`filecmp.cmp`.

   For example, ``cmpfiles('a', 'b', ['c', 'd/e'])`` will compare ``a/c`` with
   ``b/c`` and ``a/d/e`` with ``b/d/e``.  ``'c'`` and ``'d/e'`` will each be in
   one of the three returned lists.



.. function:: clear_cache()

   Clear the filecmp cache. This may be useful if a file is compared so quickly
   after it is modified that it is within the mtime resolution of
   the underlying filesystem.

   .. versionadded:: 3.4

The :class:`dircmp` class

.. data:: DEFAULT_IGNORES

   .. versionadded:: 3.4

   List of directories ignored by :class:`dircmp` by default.

Here is a simplified example of using the subdirs attribute to search recursively through two directories to show common different files:

>>> from filecmp import dircmp
>>> def print_diff_files(dcmp):
...     for name in dcmp.diff_files:
...         print("diff_file %s found in %s and %s" % (name, dcmp.left,
...               dcmp.right))
...     for sub_dcmp in dcmp.subdirs.values():
...         print_diff_files(sub_dcmp)
...
>>> dcmp = dircmp('dir1', 'dir2') # doctest: +SKIP
>>> print_diff_files(dcmp) # doctest: +SKIP