[Python-Dev] Multiple inheritance (original) (raw)

Guido van Rossum guido@digicool.com
Thu, 03 May 2001 14:50:30 -0400

Pardon if this is brief and suggestive only, I am on deadlines.

No problem. We appreciate it!

Super is a mistaken concept in multiple inheritance languages. Fortunately, Python is not brain-damaged. Its multiple inheritance model can be fixed easily to be fully capable.

Here is a suggestive example of implementing the Eiffel model (the only one that is theoretically sound) using "pretend" Python syntax (keyword conservationists might like "import" where I have "rename"):

1. The simple case, X inherits from Y and in defining foo and bar needs to use Y's version: class X (Y rename foo as sfoo, bar as sbar ): def foo (self): self.sfoo() myfoostuff

Nice! This is similar to Jeremy's favorite way of spelling "super":

class X(Y): Yfoo = Y.foo def foo(self): self.Yfoo() myfoostuff

Suppose D inherits from B and C, which both inherit from A. A has a method a1 that is redefined in B but not in C. D wishes to use both A's version as inherited via C and B's version.

class D (B rename a1 as ba1, C rename a1 as ca1): can now use self.ca1, self.a1 Renaming is also useful where you inherit from a utility class and the lingo is different in the class where you want to use it. E.g. class Window (Tree rename children as subWindows) Reference: Meyer, B. "Object-Oriented Software Construction", 2nd Edition.

Yes.

--Guido van Rossum (home page: http://www.python.org/~guido/)