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Python Object-Oriented Python Advanced Objects Math

Thomas Bynum
Thomas Bynum
4,616 Points

What is the point of a magic method?

I feel dense watching these videos, but what is the point of a magic method? I thought python knew how to add and subtract and convert to integers without me telling it how to do that. What is __add__ doing differently than a + b?

1 Answer

Chris Freeman
MOD
Chris Freeman
Treehouse Moderator 67,636 Points

Good question! All of the built-in types have magic methods like __add__, __radd__, and __iadd__ predefined so it appears that things like a+b just work. The types int, str, float, etc. all have these magic methods.

When creating user-defined classes, how to “add” two instances of a class is at best unknown. By defining the requisite magic methods, the new class can take advantage of the + operator to do interesting things.

Post back if you need more help. Good luck!!!

Thomas Bynum
Thomas Bynum
4,616 Points

Thank you! So if you wanted to for some reason make + take the input and make it all capital letters and reverse it, you could? This is just giving us control over what the "normal" functions do?

Thanks for all your great feedback by the way. I've used your answers to so many questions to make sense of all this stuff.

Chris Freeman
Chris Freeman
Treehouse Moderator 67,636 Points

Correct! The operator + and * call the methods __add__ and __mul__, respectively.

To be really crazy, you could create a new class that inherited from int then override __add__ and __mul__ with each other’s definition so that + multiplied and * added! 😜

Happy to help!