Their are many methods to do it:
os.walk
>>> import os
>>> path = '/user/Bluetooth/cramp/charm'
>>> text_files = [f for f in os.listdir(filedestination) if f.endswith('.txt')]
>>> text_files
['qwe-cn.txt', 'zxc-jp.txt', 'qwe-kr.txt', 'qwe-tw.txt', ... 'mac-10.txt']
Or
Glob
>>> import glob
>>> glob.glob('./*.txt')
['./Maths.txt', './physics.txt', './chem.txt', './bio.txt']
Or fnmatch.filter()
import fnmatch, os
print fnmatch.filter(os.listdir("/qwe"), "*.tx?") #
