[Python-Dev] Operator overloading inconsistency (bug or feature?)

[Guido van Rossum]

> Suppose that a new-style class wants to overload "*" and it
> defines two methods like this:
> 
> class Foo(object):
>     def __mul__(self,other):
>         print "__mul__"
>     def __rmul__(self,other):
>         print "__rmul__"
> 
> Python-2.2.1, if you try this, you get the following behavior:
>  
> >>> f = Foo()
> >>> f*1.0
> __mul__
> >>> 1.0*f
> __rmul__
> >>> f*1
> __mul__
> >>> 1*f
> __mul__
> 
> So here is the question: Why does the last statement in this example
> not invoke __rmul__?  In other words, why do "1.0*f" and "1*f" produce 
> different behavior.  Is this intentional?  Is this documented someplace?
> Is there a workaround?  Or are we just missing something obvious?

Aargh.  I *think* this may have to do with the hacks for sequence
repetition.  But I'm not sure.  A debug session tracing carefully
through the code is in order.

--Guido van Rossum (home page: http://www.python.org/~guido/)