class factory example needed (long)

[Gary Ruben]

I have a class factory problem. You could say that my main problem is
that I don't understand class factories.
My specific problem:
I have a class with several methods I've defined.
To this class I want to add a number of other class methods where the
method names are taken from a list.
For each list member, I want to build a method having the list member
name so that I can override another method of the same name for objects
which are instances of this class. Finally, I want my class factory
which creates the method to call the overridden method.

I'm sure my description is confusing, so I'll try to illustrate it.


import Numeric
# The Numeric module contains a whole lot of methods which operate on
certain number types

class foo:
""" this is a number type class
"""
     def __init__(self, value):
         self.value = float(value)
     def __str__(self):
         .
         . other methods here
         .

     import string
     ufuncs = string.split("""
         sqrt arccos arccosh arcsin arcsinh arctan arctanh cos cosh tan tanh
         log10 sin sinh sqrt absolute fabs floor ceil fmod exp log conjugate
         """)    # these are the methods from Numeric that I want to
override/wrap for my number type

     for u in ufuncs:
         I need something here which builds methods called sqrt(),
arccos(), etc.

     An illustrative example of the class methods I want to build with
some sort of class factory is
     def sqrt(self):
         val = Numeric.sqrt(self.value)
         return foo(Numeric.sqrt(self.value) + 42)

     def arccos(self):
         val = Numeric.arccos(self.value)
         return foo(Numeric.arccos(self.value) + 42)


if __name__ == "__main__":
     a = 9
     b = foo(7)
     print Numeric.sqrt(a)
     print Numeric.sqrt(b)


This would print
3
7

Note that the methods I want to create under program control are all
identical in form. In this example they all call the wrapped method with
an argument 42 greater than the value of the number.
Does anyone have an example where they've done something similar or
could help me out with an example?
thanks in anticipation,
Gary