In an earlier post, OS.walk in Python, I described how to use os.walk and showed some examples on how to use it in scripts.
In this article, I will show how to use the os.walk() module function to walk a directory tree, and the fnmatch module for matching file names.
What is OS.walk?
It generates 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).
dirpath # is a string, the path to the directory.
dirnames # is a list of the names of the subdirectories in dirpath (excluding ‘.’ and ‘..’).
filenames # is a list of the names of the non-directory files in dirpath.
Note that the names in the lists contain no path components.
To get a full path (which begins with top) to a file or directory in dirpath, do os.path.join(dirpath, name). For more information, please see the Python Docs.
What is Fnmatch
The fnmatch module compares file names against glob-style patterns such as used by Unix shells.
These are not the same as the more sophisticated regular expression rules. It’s purely a string matching operation.
If you find it more convenient to use a different pattern style, for example regular expressions, then simply use regex operations to match your filenames. http://www.doughellmann.com/PyMOTW/fnmatch/
What does it do?
The fnmatch module is used for the wild-card pattern matching.
fnmatch() compares a single file name against a pattern and returns a boolean indicating whether or not they match. The comparison is case-sensitive when the operating system uses a case-sensitive file system.
To test a sequence of filenames, you can use filter(). It returns a list of the names that match the pattern argument.
Find all mp3 files
This script will search for *.mp3 files from the rootPath (“/”)
import fnmatch import os rootPath = '/' pattern = '*.mp3' for root, dirs, files in os.walk(rootPath): for filename in fnmatch.filter(files, pattern): print( os.path.join(root, filename))
Search computer for specific files
This script uses ‘os.walk’ and ‘fnmatch’ with filters to search the hard-drive for all image files
import fnmatch import os images = ['*.jpg', '*.jpeg', '*.png', '*.tif', '*.tiff'] matches =  for root, dirnames, filenames in os.walk("C:\"): for extensions in images: for filename in fnmatch.filter(filenames, extensions): matches.append(os.path.join(root, filename))
There are many other (and faster) ways to do this, but now you understand the basics of it.
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