Guess an archive type (tar, zip, or rar) by its file extension

def guess_archive_type(name):
    '''
    Guess an archive type (tar, zip, or rar) by its file extension
    '''
    name = name.lower()
    for ending in ('tar', 'tar.gz', 'tgz',
                   'tar.bz2', 'tbz2', 'tbz',
                   'tar.xz', 'txz',
                   'tar.lzma', 'tlz'):
        if name.endswith('.' + ending):
            return 'tar'
    for ending in ('zip', 'rar'):
        if name.endswith('.' + ending):
            return ending
    return None