How to copy class objects?

[fredrik at pythonware.com]

matthias oberlaender wrote:
> Ok, here's a more detailed example. I want a stack containing
> only ints. Then  I want a stack containing only floats. Extending
> the pattern to other types  should be straightforward. Of course,
> neither should FloatStack be a base  class of IntStack, nor vice
> versa.

class Stack:
    def push(...):
        ...
    def pop(self):
        ...

class FloatStack(Stack):
    def push(...):
        assert isinstance(item, FloatType)
        Stack.push(...)

class IntStack(Stack):
    def push(...):
        assert isinstance(item, IntType)
        Stack.push(...)

or perhaps:

class Stack:
    type = None
    def push(...):
        assert isinstance(item, self.type)
    def pop(...):
        ...

class FloatStack(Stack):
    type = FloatType

class IntStack(Stack):
    type = IntType

the latter also allows you to configure instances on
the fly:

stack = Stack()
stack.type = TupleType

(as usual, Python works better if you use it to write
Python programs...)

Cheers /F


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