
``filecmp`` --- File and Directory Comparisons
**********************************************

**Source code:** Lib/filecmp.py

======================================================================

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

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

filecmp.cmp(f1, f2, shallow=True)

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

   Unless *shallow* is given and is false, files with identical
   ``os.stat()`` signatures are taken to be equal.

   Files that were compared using this function will not be compared
   again unless their ``os.stat()`` signature changes.

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

filecmp.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 ``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.

Example:

   >>> import filecmp
   >>> filecmp.cmp('undoc.rst', 'undoc.rst') # doctest: +SKIP
   True
   >>> filecmp.cmp('undoc.rst', 'index.rst') # doctest: +SKIP
   False


The ``dircmp`` class
====================

``dircmp`` instances are built using this constructor:

class class filecmp.dircmp(a, b, ignore=None, hide=None)

   Construct a new directory comparison object, to compare the
   directories *a* and *b*. *ignore* is a list of names to ignore, and
   defaults to ``['RCS', 'CVS', 'tags']``. *hide* is a list of names
   to hide, and defaults to ``[os.curdir, os.pardir]``.

   The ``dircmp`` class compares files by doing *shallow* comparisons
   as described for ``filecmp.cmp()``.

   The ``dircmp`` class provides the following methods:

   report()

      Print (to ``sys.stdout``) a comparison between *a* and *b*.

   report_partial_closure()

      Print a comparison between *a* and *b* and common immediate
      subdirectories.

   report_full_closure()

      Print a comparison between *a* and *b* and common subdirectories
      (recursively).

   The ``dircmp`` class offers a number of interesting attributes that
   may be used to get various bits of information about the directory
   trees being compared.

   Note that via ``__getattr__()`` hooks, all attributes are computed
   lazily, so there is no speed penalty if only those attributes which
   are lightweight to compute are used.

   left

      The directory *a*.

   right

      The directory *b*.

   left_list

      Files and subdirectories in *a*, filtered by *hide* and
      *ignore*.

   right_list

      Files and subdirectories in *b*, filtered by *hide* and
      *ignore*.

   common

      Files and subdirectories in both *a* and *b*.

   left_only

      Files and subdirectories only in *a*.

   right_only

      Files and subdirectories only in *b*.

   common_dirs

      Subdirectories in both *a* and *b*.

   common_files

      Files in both *a* and *b*

   common_funny

      Names in both *a* and *b*, such that the type differs between
      the directories, or names for which ``os.stat()`` reports an
      error.

   same_files

      Files which are identical in both *a* and *b*, using the class's
      file comparison operator.

   diff_files

      Files which are in both *a* and *b*, whose contents differ
      according to the class's file comparison operator.

   funny_files

      Files which are in both *a* and *b*, but could not be compared.

   subdirs

      A dictionary mapping names in ``common_dirs`` to ``dircmp``
      objects.

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
