Raymond writes:
If only in the C API, I would like to see just such a universalmethod alternative to classmethod. That would allow different behaviors to be assigned depending on how the method is called.
And that's exactly why I would be wary of it. One of the GREAT SIMPLICITIES of Python is that all calls are "the same". Calling a function works a particular way. Calling a callable object does the same, although the arguments are passed to __call__. Calling a classmethod does the same thing. Calling a bound method does the same thing except that the first argument is curried. Here in the Python community, we think it is a good thing that one must explicitly name "self" as an argument to methods, and that any function CAN be made a method of objects. Now you're proposing a special situation, where what appears to be a single attribute of a class object is actually TWO functions... two functions that have the same name but subtly different behavior. Right now, I presume that if I have: a = A() # a is an instance of A x = a.aMethod('abc') # this is line 1 y = A.aMethod(a, 'abc') # this is line 2 that line 1 and line 2 do the same thing. This is a direct consequence of the fact that methods in Python are just functions with an instance as the first argument. But your "universalmethod" would break this. It might be worth breaking it, if the result is some *very* readable code in a whole variety of situations. And it's certainly okay for Guido to manually create a class which behaves this way via black magic (and for most users, descriptor tricks are black magic). But to make it a regular and supported idiom, I'd want to see much better evidence that it's worthwhile, because there's an important principle at risk here, and I wouldn't want to trade away the ability to explain "methods" in two sentences: A 'method' is just a function whose first argument is 'self'. The method is an atribute of the class object, and when it is called using "a.method(args)", the instance 'a' is passed as 'self'. for a cute way of making double use of a few factory functions. -- Michael Chermside