Find a file in python

In Python 3.4 or newer you can use pathlib to do recursive globbing:

>>> import pathlib
>>> sorted(pathlib.Path('.').glob('**/*.py'))
[PosixPath('build/lib/pathlib.py'),
 PosixPath('docs/conf.py'),
 PosixPath('pathlib.py'),
 PosixPath('setup.py'),
 PosixPath('test_pathlib.py')]

Reference: https://docs.python.org/3/library/pathlib.html#pathlib.Path.glob

In Python 3.5 or newer you can also do recursive globbing like this:

>>> import glob
>>> glob.glob('**/*.txt', recursive=True)
['2.txt', 'sub/3.txt']

Reference: https://docs.python.org/3/library/glob.html#glob.glob

os.walk is the answer, this will find the first match:

import os

def find(name, path):
    for root, dirs, files in os.walk(path):
        if name in files:
            return os.path.join(root, name)

And this will find all matches:

def find_all(name, path):
    result = []
    for root, dirs, files in os.walk(path):
        if name in files:
            result.append(os.path.join(root, name))
    return result

And this will match a pattern:

import os, fnmatch
def find(pattern, path):
    result = []
    for root, dirs, files in os.walk(path):
        for name in files:
            if fnmatch.fnmatch(name, pattern):
                result.append(os.path.join(root, name))
    return result

find('*.txt', '/path/to/dir')

I used a version of os.walk and on a larger directory got times around 3.5 sec. I tried two random solutions with no great improvement, then just did:

paths = [line[2:] for line in subprocess.check_output("find . -iname '*.txt'", shell=True).splitlines()]

While it's POSIX-only, I got 0.25 sec.

From this, I believe it's entirely possible to optimise whole searching a lot in a platform-independent way, but this is where I stopped the research.