how to dynamically instantiate an object inheriting from several classes?

Arnaud Delobelle arnodel at
Fri Nov 21 23:30:16 CET 2008

Joe Strout <joe at> writes:

> I have a function that takes a reference to a class, and then
> instantiates that class (and then does several other things with the
> new instance).  This is easy enough:
>    item = cls(self, **itemArgs)
> where "cls" is the class reference, and itemArgs is obviously a set of
> keyword arguments for its __init__ method.
> But now I want to generalize this to handle a set of mix-in classes.
> Normally you use mixins by creating a class that derives from two or
> more other classes, and then instantiate that custom class.  But in my
> situation, I don't know ahead of time which mixins might be used and
> in what combination.  So I'd like to take a list of class references,
> and instantiate an object that derives from all of them, dynamically.
> Is this possible?  If so, how?

Of course it's possible: use type(name, bases, dict).

>>> class A(object): pass
>>> class B(object): pass
>>> C = type('C', (A, B), {})
>>> issubclass(C, A)
>>> issubclass(C, B)

Call-by-object'ly yours


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