module importing and variable syntax

[Aahz Maruch]

In article <3AADF3DC.1030003 at dynworks.com>,
Jeff Davis  <jdavis at dynworks.com> wrote:
>
>Module importing doesn't take a string argument, but just a "bare word" 
>(in perl terms). This means I have to know the name of the file in 
>advance, and it needs to be in the right directory, or I need to use eval().
>
>What I am trying to do is have an arbitrary string with an arbitrary 
>type (type with respect to my program, not python) access the function 
>associated with the string in the module associated with the type.
>
>For example: someone writes an extension to my program creating a new 
>object of name "O". Then some other part of the program (i.e. another 
>extended module) tries to square an instance of that object, like:
>o = O()
>o.square()
>
>However, my program is completely unaware of either "O" or "square" 
>until someone writes the module(s) and registers them with the program 
>(not writing to the main program's source).

One of the most important Python rules is "explicit is better than
implicit".  So if a person wants to register a generic class with your
module, provide a function for them to do it!

module A:

    object = None
    def register(newClass):
        global object
        object = newClass


module B:

    import A
    class Foo:
        def square(self):
            pass
    A.register(Foo)


Module C:

    import A
    import B
    o = A.object()
    o.square()
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