10.4. filecmp — File and Directory Comparisons

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.


>>> import filecmp
>>> filecmp.cmp('undoc.rst', 'undoc.rst')
>>> filecmp.cmp('undoc.rst', 'index.rst')

10.4.1. The dircmp class

dircmp instances are built using this constructor:

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 provides the following methods:

Print (to sys.stdout) a comparison between a and b.
Print a comparison between a and b and common immediate subdirectories.
Print a comparison between a and b and common subdirectories (recursively).

The dircmp 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.

Files and subdirectories in a, filtered by hide and ignore.
Files and subdirectories in b, filtered by hide and ignore.
Files and subdirectories in both a and b.
Files and subdirectories only in a.
Files and subdirectories only in b.
Subdirectories in both a and b.
Files in both a and b
Names in both a and b, such that the type differs between the directories, or names for which os.stat() reports an error.
Files which are identical in both a and b.
Files which are in both a and b, whose contents differ.
Files which are in both a and b, but could not be compared.
A dictionary mapping names in common_dirs to dircmp objects.