Python 练习3 定义类，类方法，实例方法

设计一个IP类：
设计1 要求：初始化时给定ip地址并判断ip地址的合法性
            类方法：判断ip地址合法性
            实例方法：将ip地址转化为10进制的表示形式及16进制的表示形式
   例如：192.168.168.8 十进制形式为3232278536，十六进制形式为c0a8a808
设计2 要求：扩展要求1中ip类，使其实例化时增加子网掩码定义，并在初始化是判断子网掩码的合法性
            实例方法：获取ip所属子网的网络号，广播地址，及子网内ip个数
设计1解析：
"""Ip address analyzer
Method:
dispIp: Display ip address.
intIp: Get integer of ip address.
hexIp: Get hex of ip address"""
from string import Template

class IpAddress(object):

'Ip address analyzer'

def __init__(self,ip):
'Initialize ip address and netmask'
assert IpAddress.isIp(ip),\
"ip is invalid"
self.ipAddr = ip

def isIp(cls,x):
'Determine if the ip address is valid'
aList = x.split(".")
if len(aList) != 4:
return False
else:
nList=[i for i in aList if (i.isdigit() and 0 <= int(i) <= 255)]
if len(nList) != 4: return False
else: return True
isIp=classmethod(isIp)

def __bin(self,x):
'Convert the decimal into binary,and return 8-bit binary. '
x = int(x)
if x == 0:
return '00000000'
else:
re = ''
while x > 0:
mod = x%2
x = x/2
re = str(mod) + re
differ = 8 - len(re)
re = ''.join(['0' for i in range(differ)]) + re
return re

def dispIp(self):
'Display ip address'
template = Template('IP: ${ipAddr}')
print template.substitute(ipAddr=self.ipAddr)

def intIp(self):
'Return integer of the ip address'
aList = self.ipAddr.split(".")
str2 = ''.join(self.__bin(i) for i in aList)
return str(int(str2, 2))

def hexIp(self):
'Return hex of the ip address'
aList = self.ipAddr.split(".")
retu