What is the purpose of Zope Interfaces

Question

I have recently started using Zope interfaces in my code and they are only documentation. I use them to specify what attributes the class should possess, explicitly implement them in the appropriate classes and explicitly check for them where I expect one. But What should I do if I would like them to do more such as verify that the class has implemented the interface, instead of just verifying that I have said that the class implements the interface. I have read the zope wiki a couple of times, but still cannot see much more use for interfaces than what I am currently doing.  What else can you use these interfaces for, and how do you use them for more?

Can anyone help me with this?

Answer 1

You can actually test if your object or class implements your interface. For that you can use verify module.

For example:

>>> from zope.interface import Interface, Attribute, implements
>>> class IFoo(Interface):
...     x = Attribute("The X attribute")
...     y = Attribute("The Y attribute")

>>> class Foo(object):
...     implements(IFoo)
...     x = 1
...     def __init__(self):
...         self.y = 2

>>> from zope.interface.verify import verifyObject
>>> verifyObject(IFoo, Foo())
True

>>> from zope.interface.verify import verifyClass
>>> verifyClass(IFoo, Foo)
True