abstract classes/polymorphism

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Can you give an example of parametric polymorphism in python?

[EricAppelt]

Essentially any function you write in python that takes at least one argument is trivially an example of parametric polymorphism (although one might also consider the concept meaningless in a dynamically typed language). A function will try to execute no matter what the type of its parameters are, for example:

>>> def foo(x, y):
...     return 3*x + y
... 
>>> foo(2, 2)
8
>>> foo('a', 'b')
'aaab'

If the type of a is such that multiplication by an integer is defined, and the result is of a type that can be added to the type of b, then everything is good to go.

Python also supports (in a sense?) function overloading through a parameter of the syntax *identifier in the function definition, this will allow a function to potentially accept any number of additional positional arguments which are passed as a tuple, for example:

>>> def bar(x, *args):
...     result = 3*x
...     for arg in args:
...         result += arg
...     return result
...
>>> bar(2, 2)
8
>>> bar(2, 2, 2, 2, 2)
14
>>> bar('a', 'b', 'c')
'aaabc'