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

David Beazley beazley@cs.uchicago.edu
Thu, 8 Aug 2002 08:46:47 -0500 (CDT)

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
>>> 1.0*f
>>> f*1
>>> 1*f

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?