Walking Directory Trees(Python Cookbook 2-16)

Precondition

1. os.walk(top[, topdown=True[, onerror=None[, followlinks=False]]])

Generate the file names in a directory tree by walking the tree either top-down or bottom-up. For each directory in the tree rooted at directory top (including top itself), it yields a 3-tuple (dirpath, dirnames, filenames).

Example

for root, dirs, files in os.walk('C:\\Download'):
    for name in files:
        print os.path.join(root, name)

        Output: C:\Download\27257633.flv
                     C:\Download\27294059.flv

2. fnmatch.fnmatch(filename, pattern)

Test whether the filename string matches the pattern string, returning true or false. If the operating system is case-insensitive, then both parameters will be normalized to all lower- or upper-case before the comparison is performed. If you require a case-sensitive comparison regardless of whether that’s standard for your operating system, use fnmatchcase() instead.

Example

if fnmatch.fnmatch('test.txt', '*.txt'):
    print 'Y'

Output:Y

 

Problem

You need to examine a "directory", or an entire directory tree rooted in a certain directory, and iterate on the files (and optionally folders) that match certain patterns.

Solution

 1>>> import os, fnmatch
 2>>> def all_files(root, patterns='*', single_level=False, yield_folders=False):
 3    patterns = patterns.split(';')
 4    for path, dirs, files in os.walk(root):
 5        if yield_folders:
 6            files.extend(dirs)
 7        files.sort()
 8        for name in files:
 9            for pattern in patterns:
                if fnmatch.fnmatch(name, pattern):
                    yield os.path.join(path, name)
                    break
        if single_level:
            break

 

Usage

for s in all_files('C:\\Download', '*.flv;*.mp4'):
    print s

Output: C:\Download\27257633.flv
             C:\Download\27294059.flv
             C:\Download\cd1.mp4