10.5. "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])

   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])

   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') 
   True
   >>> filecmp.cmp('undoc.rst', 'index.rst') 
   False


10.5.1. The "dircmp" class
==========================

"dircmp" instances are built using this constructor:

class filecmp.dircmp(a, b[, ignore[, hide]])

   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') 
   >>> print_diff_files(dcmp) 
