gistfile1.py

def custom_cmp(item1, item2):
    """ Helper function to use as 'cmp' parameter when sorting the list of
        .png pages in the unzipped pages images list.
    """
    n1 = item1.split('.')[0][4:]
    n2 = item2.split('.')[0][4:]
    return int(n1) - int(n2)