python遍历一个网段的ip地址

def ip2num(ip):#ip to int num
    lp = [int(x) for x in ip.split('.')]
    return lp[0] << 24 | lp[1] << 16 | lp[2] << 8 | lp[3]

def num2ip(num):# int num to ip
    ip = ['', '', '', '']
    ip[3] = (num & 0xff)
    ip[2] = (num & 0xff00) >> 8
    ip[1] = (num & 0xff0000) >> 16
    ip[0] = (num & 0xff000000) >> 24
    return '%s.%s.%s.%s' % (ip[0], ip[1], ip[2], ip[3])

def iprange(ip1,ip2):
    # print ip1,ip2
    # return ip1, ip2, 3
    num1 = ip2num(ip1)
    num2 = ip2num(ip2)

    tmp = num2 - num1
    if tmp < 0:
        return None
    else:
        return num1, num2, tmp

python的返回值特点简直是神的不行