实际上，由于python是动态语言，支持多继承，因此接口在语言层面，是没有的东东。
然后，在架构设计上，我们又需要这么一个东西，来规范开发人员的行为。
因此就有了zope.interface的诞生。
定义接口
继承 zope.interface.Interface即可，如下：
import zope.interface
class IFoo(zope.interface.Interface):
"""Foo blah blah"""
x = zope.interface.Attribute("""x blah blah""")
def bar(q, r=None):
"""bar blah blah"""
1. 接口不是类
>>> type(IFoo)
<class 'zope.interface.interface.InterfaceClass'>
>>> class A(object):
pass >>> type(A)
<type 'type'>
但能正常访问：__dict__ / __name__ / __module__ / __doc__ 等专有属性
2. 行为有点类似于字典
>>> list(IFoo)
['x', 'bar']
>>> IFoo.get('bar')
<zope.interface.interface.Method object at 0x0000000002B7B710>
>>> callable(IFoo.get('bar'))
True
3. 接口中的方法能自动获取签名
>>> IFoo['bar'].getSignatureString()
'(q, r=None)'
实现接口
在声明接口之前，有两个术语要说明下：
provide(提供接口)
对象实例(object)提供接口，接口详细描述/规范了对象的行为。
implement(实现)
类(可以抽象成工厂类)实现(implement)接口。
类一般不会提供(provide)接口。只有对象提供接口。【备注：此处属于术语概念，了解即可】
1. 实现接口：
a). 用类实现
>>> class Foo:
zope.interface.implements(IFoo)
有点诧异：没有报错！对象实例呢？
>>> f = Foo()
也没有报错！然后下面却报错了：
>>> IFoo['bar'](1) Traceback (most recent call last):
File "<pyshell#85>", line 1, in <module>
IFoo['bar'](1)
File "C:\Python27\lib\site-packages\zope\interface\interface.py", line 616, in __call__
raise BrokenImplementation(self.interface, self.__name__)
BrokenImplementation: An object has failed to implement interface <InterfaceClass __main__.IFoo> The bar attribute was not provided.
问题：该如何在子类的实例中使用接口里面定义的方法？
如何规范开发人员的行为？
答案是：通过测试来发现对象或者类是否实现了定义的接口。通过代码测试来做。通过测试控制开发，似乎有点马后炮。
主要使用 zope.interface.verify 里面的 verifyObject 和 verifyClass方法。可以参考这里。
>>> class IFoo(Interface):
x = Attribute("The X attribute")
def bar(q,r=None):
"""bar of interface""" >>> class Foo:
implements(IFoo) >>> from zope.interface.verify import verifyObject, verifyClass
>>> verifyObject(IFoo, Foo()) Traceback (most recent call last):
File "<pyshell#13>", line 1, in <module>
verifyObject(IFoo, Foo())
File "C:\Python27\lib\site-packages\zope\interface\verify.py", line 105, in verifyObject
return _verify(iface, candidate, tentative, vtype='o')
File "C:\Python27\lib\site-packages\zope\interface\verify.py", line 62, in _verify
raise BrokenImplementation(iface, name)
BrokenImplementation: An object has failed to implement interface <InterfaceClass __main__.IFoo> The x attribute was not provided. >>> verifyClass(IFoo, Foo) Traceback (most recent call last):
File "<pyshell#14>", line 1, in <module>
verifyClass(IFoo, Foo)
File "C:\Python27\lib\site-packages\zope\interface\verify.py", line 102, in verifyClass
return _verify(iface, candidate, tentative, vtype='c')
File "C:\Python27\lib\site-packages\zope\interface\verify.py", line 62, in _verify
raise BrokenImplementation(iface, name)
BrokenImplementation: An object has failed to implement interface <InterfaceClass __main__.IFoo> The bar attribute was not provided.
b) 用实例变量实现：
>>> b= Foo()
>>> b = zope.interface.implementer(IFoo)(b)
>>> list(zope.interface.providedBy(b))
[<InterfaceClass __main__.IFoo>]
在python 2.6后，可以直接用修饰符，上面代码的等同代码如下：
>>> from zope.interface import implementer
>>> @implementer(IFoo)
class Foo:
pass >>> list(zope.interface.implementedBy(Foo))
[<InterfaceClass __main__.IFoo>]
2. 查看类实现了哪些接口
>>> list(zope.interface.implementedBy(Foo))
[<InterfaceClass __main__.IFoo>]
测试某接口是否由某类实现：
>>> IFoo.implementedBy(Foo)
True
3. 查看对象实例实现了哪些接口
>>> list(zope.interface.providedBy(f))
[<InterfaceClass __main__.IFoo>]
测试某接口是否由某对象提供
>>> IFoo.providedBy(f)
True
接口的继承
与python的类继承相似。又有所不同，接口继承不是深度优先，如下：
>>> import zope.interface
>>> class IBase(zope.interface.Interface):
def foo():
"""base foo doc""" >>> class IBase1(IBase):
pass >>> class IBase2(IBase):
def foo():
"""base2 foo doc""" >>> class ISub(IBase1, IBase2):
pass >>> ISub['foo'].__doc__
'base2 foo doc'
类的继承：
>>> class Base:
def foo(self):
print "base" >>> class Base1(Base):
pass >>> class Base2(Base):
def foo(self):
print "base2" >>> class Sub(Base1,Base2):
pass >>> Sub().foo()
base