Python CIDR地址块算法

#!/usr/bin/env python# -*- encoding: utf-8 -*-   def stringxor(str1, str2):    orxstr = ""    for i in range(0, len(str1)):        rst = int(str1[i]) & int(str2[i])        orxstr = orxstr + str(rst)    return orxstr  def bin2dec(string_num):    return str(int(string_num, 2))  def getip(ip, type):    result = ''    for i in range(4):        item = bin2dec(ip[0:8])        if i == 3:            if type == 0:                item = str(int(item) + 1)            else:                item = str(int(item) - 1)        result = result + item + '.'        ip = ip[8:]    return result.strip('.') def CIDR(input):    try:        ip = input.split('/')[0]        pos = int(input.split('/')[1])        ipstr = ''        for i in ip.split('.'):            ipstr = ipstr + bin(int(i)).replace('0b', '').zfill(8)        pstr = '1' * pos + '0' * (32 - pos)        res = stringxor(ipstr, pstr)        _ip = getip(res, 0), getip(res[0:pos] + '1' * (32 - pos), 1)        return _ip[0] + "-" + _ip[1]    except:        return input  def get_ip_list(ip):    ip_list_tmp = []    iptonum = lambda x: sum([256 ** j * int(i) for j, i in enumerate(x.split('.')[::-1])])    numtoip = lambda x: '.'.join([str(x / (256 ** i) % 256) for i in range(3, -1, -1)])    if '-' in ip:        ip_range = ip.split('-')        ip_start = long(iptonum(ip_range[0]))        ip_end = long(iptonum(ip_range[1]))        ip_count = ip_end - ip_start        if ip_count >= 0 and ip_count <= 655360:            for ip_num in range(ip_start, ip_end + 1):                ip_list_tmp.append(numtoip(ip_num))        else:            print 'IP format error'    else:        ip_split = ip.split('.')        net = len(ip_split)        if net == 2:            for b in range(1, 255):                for c in range(1, 255):                    ip = "%s.%s.%d.%d" % (ip_split[0], ip_split[1], b, c)                    ip_list_tmp.append(ip)        elif net == 3:            for c in range(1, 255):                ip = "%s.%s.%s.%d" % (ip_split[0], ip_split[1], ip_split[2], c)                ip_list_tmp.append(ip)        elif net == 4:            ip_list_tmp.append(ip)        else:            print "IP format error"    return ip_list_tmp ip = "255.168.2.1/21"print get_ip_list(CIDR(ip))