From: "Nathan Clegg" <nathan@geerbox.com>
"Oren" == Oren Tirosh <oren-py-d@hishome.net> writes:
Oren> I would like to be able to declare that I need an object Oren> with a specific interface even if the object was written Oren> long before and I don't want to modify an existing library Oren> just to make it conform to my interface names.
class InterfaceWrapper(ExistingClass, AbstractInterfaceClass): pass
I'm not saying this is a good idea :), but I believe this problem is already solvable in the current language. The wrapper class should pass the test of isinstance for the interface class, but the existing class as the first parent should implement all of the calls.
Note that most other languages that actually support proper interfaces (i.e. Java) would have similar trouble adding an interface to a prior existing class without modifying its definition. Python actually provides a much simpler solution than others might, it seems to me.
The problem is that we want to use ExistingClass *objects* where AbstractInterfaceClass is required. If someone else has written a module containing: def some_fantastic_function(AbstractInterfaceClass: x) ... And I have written a function: def my_func(generator) for x in generator: some_fantastic_function(x) If there's a generator lying about which produces ExistingClass, I ought to be able to pass it to my_func. ----------------------------------------------------------- David Abrahams * Boost Consulting dave@boost-consulting.com * http://www.boost-consulting.com