Python: multiplication override

Question

So, I’ve got a custom class that has a __mul__ function which works with ints. However, in my program (in libraries), it’s getting called the other way around, i.e., 2 * x where x is of my class. Is there a way I can have it use my __mul__ function for this?

Asked By: Colin DeClue

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Source

Answer 1

Just add the following to the class definition and you should be good to go:

__rmul__ = __mul__

Answered By: Karl Knechtel

Answer 2

Implement __rmul__ as well.

class Foo(object):
    def __mul__(self, other):
        print '__mul__'
        return other
    def __rmul__(self, other):
        print '__rmul__'
        return other

x = Foo()
2 * x # __rmul__
x * 2 # __mul__

Answered By: Cat Plus Plus

Python: multiplication override

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