Use os.listdir(), listing files in current directory:

import os
arr = os.listdir()
print(arr)

Use glob, listing by regular expression:

import glob

listFiles = []
for file in glob.glob("*.txt"):
    listFiles.append(file)

Source has an excellent answer to this question, further usage can be found in the source.

Source:
https://stackoverflow.com/questions/3207219/how-do-i-list-all-files-of-a-directory