Got it: #!/usr/bin/env python from PIL import Image import glob, os, re
size = 128, 128 def thumbnailer(dir, filenameRx): for picture in [ p for p in os.listdir(dir) if os.path.isfile(os.path.join( dir,p)) and filenameRx.match(p) ]: file, ext = os.path.splitext(picture) im = Image.open (picture) im.thumbnail(size, Image.ANTIALIAS) im.save(file + ".thumbnail" + ext) jpg = re.compile(".*\.(jpg|jpeg)", re.IGNORECASE) thumbnailer(".", jpg) The answer was sitting in front of my eyes. What is your code doing? It looks like: for $foo in [current working directory] if $foo is a file and foo's name matches the regex -- http://mail.python.org/mailman/listinfo/python-list