Python Polymorphism

[Fredrik Lundh]

Carlos Moreira wrote:

> Supose that I want to create two methos (inside a
> class) with exactly same name, but number of
> parameters different:

that's known as multimethods, or multiple dispatch.  it's a kind of
polymorphism; it's not the only way to do it, nor is it the only thing
that qualifies as polymorphism.

(in OO lingo, polymorphism usually means that a variable can hold
objects of different types/classes, and that the language can per-
form a given operation on an object without having to know in ad-
vance what type/class it belongs to).

Python only supports single-dispatch in itself, but you can use the
existing mechanisms to implement multimethods in different ways.
for some ways to do it, see:

    http://www.artima.com/weblogs/viewpost.jsp?thread=101605
    http://www-106.ibm.com/developerworks/library/l-pydisp.html

however, solving your problem is of course trivial; just change

> class myClass:
>      myAttribute = 0
>      def myMethod(self):
>           self.myAttribute += 1
>      def myMethod(self, myValue):
>           self.myAttribute += myValue

to

    class myClass:
        myAttribute = 0
        def myMethod(self, myValue=1):
            self.myAttribute += myValue

and you're done.

> I want to use the power of polymorphism to modelate
> the problem.

the problem you described can be trivially solved with a default
argument.  maybe you should come up with a more realistic pro-
blem?

</F>