Python Cookbook

Walking Directory Trees

Credit: Robin Parmar, Alex Martelli

Problem

You need to examine a directory, or an entire directory tree rooted in a certain directory, and obtain a list of all the files (and optionally folders) that match a certain pattern.

Solution

os.path.walk is sufficient for this purpose, but we can pretty it up quite at bit:

import os.path, fnmatch

def listFiles(root, patterns='*', recurse=1, return_folders=0):

    # Expand patterns from semicolon-separated string to list
    pattern_list = patterns.split(';')
    # Collect input and output arguments into one bunch
    class Bunch:
        def _ _init_ _(self, **kwds): self._ _dict_ _.update(kwds)
    arg = Bunch(recurse=recurse, pattern_list=pattern_list,
        return_folders=return_folders, results=[])

    def visit(arg, dirname, files):
        # Append to arg.results all relevant files (and perhaps folders)
        for name in files:
            fullname = os.path.normpath(os.path.join(dirname, name))
            if arg.return_folders or os.path.isfile(fullname):
                for pattern in arg.pattern_list:
                    if fnmatch.fnmatch(name, pattern):
                        arg.results.append(fullname)
                        break
        # Block recursion if recursion was disallowed
        if not arg.recurse: files[:]=[]

    os.path.walk(root, visit, arg)

    return arg.results

Discussion

The standard directory-tree function os.path.walk is powerful and flexible, but it can be confusing to beginners. This recipe dresses it up in a listFiles function that lets you choose the root folder, whether to recurse down through subfolders, the file patterns to match, and whether to include ...