[Python-Dev] Classes and Metaclasses in Smalltalk (original) (raw)

Tim Peters tim.one@home.com
Thu, 3 May 2001 01:49:04 -0400

[MAL, on basemethods]

... In other words: you let Python continue the search for the method as if it hadn't found the occurrance calling the bsaemethod() API. Hmm, still not clear enough... better let Tim jump in here (we've had a discussion about basemethod() some months or years ago). Tim ?

Sorry, I'm not sure what either of you is talking about. In

class A(B, C): def foo(self): super.foo()

Guido said that super would start searching at B, but I don't know what your "continue the search for the method as if it hadn't found the occurrance calling the bsaemethod() API" means: defining what a thing does in terms of an unspecified API it doesn't use is a pretty sure recipe for compounded confusion .

Given that we're using Python's search rules, the ambiguous point remaining is whether:

super.f()

textually contained in a method of class K begins searching with:

1) K.__bases__

or with:

2) self.__class__.__bases__

Java uses #1, and Guido's "the search starts with B" implies that he would too. But it's unclear whether he meant that. Given also

class D(A): def foo(self): super.foo()

D().foo()

both views agree that D.foo() is invoked first, and that D.foo() invokes A.foo() next. But under #1 A.foo() invokes C.foo() or D.foo() next, while under #2 A.foo() invokes A.foo() again. Multiple inheritance is a red herring here -- take C out of A's bases, and the same ambiguity needs to be resolved.