You need to write a script that involves finding files, like a file renaming script or a log

archiver utility, but you’d rather not have to call shell utilities from within your Python

script, or you want to provide specialized behavior not easily available by “shelling out.”

To search for files, use the os.walk() function, supplying it with the top-level directory.

Here is an example of a function that finds a specific filename and prints out the full

path of all matches:

#!/usr/bin/env python3.3

import os

def findfile(start, name):

for relpath, dirs, files in os.walk(start):

if name in files:

full_path = os.path.join(start, relpath, name)

print(os.path.normpath(os.path.abspath(full_path)))

if __name__ == '__main__':

findfile(sys.argv[1], sys.argv[2])

bash % ./findfile.py . myfile.txt

The os.walk() method traverses the directory hierarchy for us, and for each directory

it enters, it returns a 3-tuple, containing the relative path to the directory it’s inspecting,

a list containing all of the directory names in that directory, and a list of filenames in

that directory.

For each tuple, you simply check if the target filename is in the files list. If it is,

os.path.join() is used to put together a path. To avoid the possibility of weird looking

paths like ././foo//bar, two additional functions are used to fix the result. The first is

os.path.abspath(), which takes a path that might be relative and forms the absolute

path, and the second is os.path.normpath(), which will normalize the path, thereby

resolving issues with double slashes, multiple references to the current directory, and

so on.

Although this script is pretty simple compared to the features of the find utility found

on UNIX platforms, it has the benefit of being cross-platform. Furthermore, a lot of

additional functionality can be added in a portable manner without much more work.

To illustrate, here is a function that prints out all of the files that have a recent modifi‐

cation time:

#!/usr/bin/env python3.3

import os

import time

def modified_within(top, seconds):

now = time.time()

for path, dirs, files in os.walk(top):

for name in files:

fullpath = os.path.join(path, name)

if os.path.exists(fullpath):

mtime = os.path.getmtime(fullpath)

if mtime > (now - seconds):

print(fullpath)

if __name__ == '__main__':

import sys

if len(sys.argv) != 3:

print('Usage: {} dir seconds'.format(sys.argv[0]))

raise SystemExit(1)

modified_within(sys.argv[1], float(sys.argv[2]))

It wouldn’t take long for you to build far more complex operations on top of this little

function using various features of the os, os.path, glob, and similar modules. See Rec‐

ipes 5.11 and 5.13 for related recipes.