Hi,
I've made a try of a function that check object/class members for duck typing.

For now I've basically called it isducktype(X, A)
it returns true if:
- X has all attributes of A
- X methods have same number of arguments than corresponding A methods

or if A.__ducktypecheck__(X) returns True

Behaviour looks like isinstance and issubclass (support tuples...).

To test it:
The patch with example is here:
https://gist.github.com/apieum/7751279


Any opinion about a feature like this ?