Get a filtered list of files in a directory

Question

I am trying to get a list of files in a directory using Python, but I do not want a list of ALL the files.

What I essentially want is the ability to do something like the following but using Python and not executing ls.

ls 145592*.jpg

If there is no built-in method for this, I am currently thinking of writing a for loop to iterate through the results of an os.listdir() and to append all the matching files to a new list.

However, there are a lot of files in that directory and therefore I am hoping there is a more efficient method (or a built-in method).

Solution 1

import glob

jpgFilenamesList = glob.glob('145592*.jpg')

See glob in python documenttion

Solution 2

glob.glob() is definitely the way to do it (as per Ignacio). However, if you do need more complicated matching, you can do it with a list comprehension and re.match(), something like so:

files = [f for f in os.listdir('.') if re.match(r'[0-9]+.*\.jpg', f)]

More flexible, but as you note, less efficient.

Solution 3

Keep it simple:

import os
relevant_path = "[path to folder]"
included_extensions = ['jpg','jpeg', 'bmp', 'png', 'gif']
file_names = [fn for fn in os.listdir(relevant_path)
              if any(fn.endswith(ext) for ext in included_extensions)]

I prefer this form of list comprehensions because it reads well in English.

I read the fourth line as: For each fn in os.listdir for my path, give me only the ones that match any one of my included extensions.

It may be hard for novice python programmers to really get used to using list comprehensions for filtering, and it can have some memory overhead for very large data sets, but for listing a directory and other simple string filtering tasks, list comprehensions lead to more clean documentable code.

The only thing about this design is that it doesn't protect you against making the mistake of passing a string instead of a list. For example if you accidentally convert a string to a list and end up checking against all the characters of a string, you could end up getting a slew of false positives.

But it's better to have a problem that's easy to fix than a solution that's hard to understand.

Solution 4

Another option:

>>> import os, fnmatch
>>> fnmatch.filter(os.listdir('.'), '*.py')
['manage.py']

https://docs.python.org/3/library/fnmatch.html

Solution 5

Filter with glob module:

Import glob

import glob

Wild Cards:

files=glob.glob("data/*")
print(files)

Out:

['data/ks_10000_0', 'data/ks_1000_0', 'data/ks_100_0', 'data/ks_100_1',
'data/ks_100_2', 'data/ks_106_0', 'data/ks_19_0', 'data/ks_200_0', 'data/ks_200_1', 
'data/ks_300_0', 'data/ks_30_0', 'data/ks_400_0', 'data/ks_40_0', 'data/ks_45_0', 
'data/ks_4_0', 'data/ks_500_0', 'data/ks_50_0', 'data/ks_50_1', 'data/ks_60_0', 
'data/ks_82_0', 'data/ks_lecture_dp_1', 'data/ks_lecture_dp_2']

Fiter extension .txt:

files = glob.glob("/home/ach/*/*.txt")

A single character

glob.glob("/home/ach/file?.txt")

Number Ranges

glob.glob("/home/ach/*[0-9]*")

Alphabet Ranges

glob.glob("/home/ach/[a-c]*")

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