Interfaces

Adds interfaces to Python. Loosely based on either Java interfaces, or Haskell typeclasses. This provides some informal assurances to client code that your class or objects behave in a certain fashion.

To create an interface, subclass Interface, and add fill out the __name__ and __interface__ fields. Also, adding comments is very necessary, as the details of the interface are left unspecified.

• __name__ is a pretty name for your interface
• __interface__ is a list of attributes that implementors are required to support.

importinterfacesclassStrable(Interface):
'''Anything that can be converted to a (pretty) string. To implement, define a function __str__ like so: def __str__(self): return "Pretty description of " + self.name '''__name__='Strable'__interface__= [ '__str__', # obj.__str__(self) returns a pretty string
]

Then, to declare that a class is Strable, we use the @implements decorator:

@implements(Strable)classMyClass:
def__init__(self, name="Fred"):
self.name=namedef__str__(self):
return"A "+self.name

Of course, the raison d'etre of interfaces is so that you can test for them:

ifimplements(myobj, Strable):
print"Foo with your "+str(myobj)