def natural_sort(list, key=lambda s:s):
    def get_alphanum_key_func(key):
        convert = lambda text: int(text) if text.isdigit() else text
        return lambda s: [convert(c) for c in re.split('([0-9]+)', key(s))]
    sort_key = get_alphanum_key_func(key)
    list.sort(key=sort_key)