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waleed aljarman
1,657 PointsDo Magic Methods run according to order?
https://teamtreehouse.com/library/math
In defining the radd and iadd, he didn't use int(self), is it because it's already an int from before?
1 Answer
Josh Keenan
20,315 PointsNo, they are ran when called. So the __add__ is actually the same as my_object.add() they aren't ran when defined, just defined. With regards to __radd__, it is right side add.
length = Length(5, "m") + 5 # our imaginary class is Length, and taking that and adding 5 to it
length = 5 + Length (5, "m") . # now we try taking 5 and adding a length to it
The first line here works fine, because we are also going to assume we have defined our __add__ for the class. It knows it is just adding 5 to the class value.
The second line however tries to add our class Length to the integer 5, and the integer 5 is calling the int.__add__ method when it is adding the two, and it doesn't know how to handle adding our new class to an integer. This is where __radd__ comes in, it tries to do int.__add__ and if that doesn't work it tries to use Length.__radd__ which we will say looks like this:
def __radd__(self, other):
return Length.__add__(self,other)
Now the interpreter will run Length.__radd__ and add the two. Hope this makes sense and feel free to ask any questions