Handle Unix-style filename comparison with the fnmatch module.



Module: fnmatch
Purpose: Compare filenames against Unix-style glob patterns.
Python Version: 1.4 and later.

Description:

The fnmatch module is used to compare filenames against glob-style patterns such as used by Unix shells.

Simple Matching:

fnmatch() compares a single filename against a pattern and returns a boolean indicating whether or not they match. If the operating system uses a case-insensitive filesystem, the comparison is not case sensitive. Otherwise it is.

import fnmatch
import os

pattern = 'fnmatch_*.py'
print 'Pattern :', pattern
print

files = os.listdir('.')
for name in files:
 print 'Filename: %-25s %s' % (name, fnmatch.fnmatch(name, pattern))


In this example, the pattern matches all files starting with ‘fnmatch_’ and ending in ‘.py’.


$ python fnmatch_fnmatch.py
Pattern : fnmatch_*.py

Filename: .svn                      False
Filename: __init__.py               False
Filename: fnmatch_filter.py         True
Filename: fnmatch_fnmatch.py        True
Filename: fnmatch_fnmatchcase.py    True
Filename: fnmatch_translate.py      True


To force a case-sensitive comparison, regardless of the filesystem and operating system settings, use fnmatchcase().

import fnmatch
import os

pattern = 'FNMATCH_*.PY'
print 'Pattern :', pattern
print

files = os.listdir('.')

for name in files:
 print 'Filename: %-25s %s' % (name, fnmatch.fnmatchcase(name, pattern))


Since my laptop uses a case-sensitive filesystem, no files match the modified pattern.


$ python fnmatch_fnmatchcase.py
Pattern : FNMATCH_*.PY

Filename: .svn                      False
Filename: __init__.py               False
Filename: fnmatch_filter.py         False
Filename: fnmatch_fnmatch.py        False
Filename: fnmatch_fnmatchcase.py    False
Filename: fnmatch_translate.py      False


Filtering:

To test a sequence of filenames, you can use filter(). It returns a list of the names that match the pattern argument.

import fnmatch
import os

pattern = 'fnmatch_*.py'
print 'Pattern :', pattern

files = os.listdir('.')
print 'Files   :', files

print 'Matches :', fnmatch.filter(files, pattern)


In this example, filter() returns the list of names of the example source files associated with this post.


$ python fnmatch_filter.py
Pattern : fnmatch_*.py
Files   : ['.svn', '__init__.py', 'fnmatch_filter.py', 'fnmatch_fnmatch.py', 'fnmatch_fnmatchcase.py', 'fnmatch_translate.py']
Matches : ['fnmatch_filter.py', 'fnmatch_fnmatch.py', 'fnmatch_fnmatchcase.py', 'fnmatch_translate.py']


Translating Patterns:

Internally, fnmatch converts the glob pattern to a regular expression and uses the re module to compare the name and pattern. The translate() function is the public API for converting glob patterns to regular expressions.

import fnmatch

pattern = 'fnmatch_*.py'
print 'Pattern :', pattern
print 'Regex   :', fnmatch.translate(pattern)


Notice that some of the characters are escaped to make a valid expression.


$ python fnmatch_translate.py
Pattern : fnmatch_*.py
Regex   : fnmatch\_.*\.py$



References:

PyMOTW: glob
glob module documentation
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