zope.interface安装包下载地址：https://pypi.python.org/pypi/zope.interface#downloads
使用zope.interface的实例：
#coding=utf8
from zope.interface import Interface, implements
class addClass:
def add(self,a,b):
"""comments"""
class overAdd():
implements(addClass)
def add(self,a,b):
print a+b或者
#coding=utf8
from zope.interface import Interface, implements
class addClass:
def add(self,a,b):
"""comments"""
@implementer(addClass):
class overAdd():
def add(self,a,b):
print a+b