[Tutor] overloading binary operator for mixed types: a no-no?

[Alex Hunsley]

I'm writing a Vector class (think Vector as in the mathematical vector)...
A critical snippet is as follows:

class Vector(lister.Lister):
    def __init__(self, *elems):
        # ensure that we create a list, not a tuple
        self.elems = list(elems)

    def __add__(self, other):
        return map(lambda x,y: x + y , self.elems, other.elems)

    def __mult__(self, other):
        return map(lambda x,y: x * y , self.elems, [other])


The overloading of + (add) works fine:

  >>> a=Vector(1,2,3)
  >>> a+a
  [2, 4, 6]

But of course, I have problems with mult. When using vectors, it would 
seem to make sense to overload the * (multiply) operator to mean 
multiply a vector by a scalar as this would be the common usage in 
maths/physics. (I've made a seperate method call dotProduct for dot 
products for sake of clarity.)

Anyway, my multiply doesn't work of course:

  >>> a=Vector(1,2,3)
  >>> a * 2
  Traceback (most recent call last):
    File "<interactive input>", line 1, in ?
  TypeError: unsupported operand type(s) for *: 'instance' and 'int'

... presumably because overloading binary operators like * requires that 
both operands be instances of the class in question!
My question is: is there any way to overload * for my Vector class so 
that notation like (a * 2) would work, and call __mult__ or similar? Or 
should I just bite the bullet and write a normal method called 
'multiply'? ('scale' would be better actually.)

thanks
alex