operator overload python custom class

Question

say I want to overload an operator (lets say + for now) for some class I've created,

class A (object):
    #code here

and then:

a = A()
b = A()

what would I do to define:

c = a + b

or something along those lines? (note: this question is purely theoretical I will likely use this at some time, just not currently (unless its really easy and I really need a use for it))

(p.s. if it is possible to do this for other things such as and, or, not, str, e.t.c.)

score 4 · Accepted Answer · answered Jul 03 '14 at 23:32

4

Since A is the first operand of the binary operator, you should define A.__add__(). If A was the second operand and there was no way to change the class of the first operand, you would have to define A.__radd__().

Full reference for magic methods

answered Jul 03 '14 at 23:32

Ignacio Vazquez-Abrams

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thank you, is their a way to do this for `and` or `or` or `not`? – tox123 Jul 04 '14 at 01:44
http://stackoverflow.com/questions/471546/any-way-to-override-the-and-operator-in-python – Ignacio Vazquez-Abrams Jul 04 '14 at 01:46
lets say I would like to `def __pow__(self, y)` outside of a class. Better yet redefine it for say the list type. How would I do that? is it even possible? – tox123 Jul 05 '14 at 01:53
1

Defining methods outside a class and monkeypatching them after is possible. Doing it with a magic method is questionable. But monkeypatching a type defined in C is impossible. – Ignacio Vazquez-Abrams Jul 05 '14 at 01:55
oh! I didn't know lists were predefined in C! – tox123 Jul 05 '14 at 02:01

operator overload python custom class

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