用python 将数字每三组分割

def cut_num(n, sep=‘,‘):
    # 第一个参数是要传递的数字,第二个是分隔符
    s = str(abs(n))[::-1]
    groups = []
    i = 0
    while i < len(s):
        groups.append(s[i:i + 3])
        i += 3
    retval = sep.join(groups)[::-1]
    if n < 0:
        return ‘-%s‘ % retval
    else:
        return retval