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.)

Ignacio Vazquez-Abrams · Accepted Answer · 2014-07-03 23:32:40Z

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 3, 2014 at 23:32

Ignacio Vazquez-Abrams

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5 Comments

tox123 Over a year ago

thank you, is their a way to do this for and or or or not?

Ignacio Vazquez-Abrams Over a year ago

stackoverflow.com/questions/471546/…

tox123 Over a year ago

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?

Ignacio Vazquez-Abrams Over a year ago

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.

tox123 Over a year ago

oh! I didn't know lists were predefined in C!

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