Earlier quoted context omitted.
Looking at eliteraspberrie's example, not really. Python's __iadd__ and such are not able to reassign. There is no "inout" in Python. The assignment aspect of __iadd__ is done through self mutation (and an extra hard-coded assignment to support immutable variables).
The assignment aspect of __iadd__ is done like any other assignment in python. The one to one equivalent of eliteraspberrie's would be: class Vector2D: def __iadd__(self, other) return self + other No "self mutation" as you suggest. a += b is equivalent to a = a.__iadd__(b)
Your example would be the implementation for immutable Vector2Ds, and is implemented for you if you just wrote __add__. (I presume object.__iadd__ falls back to self.__add__.)
The only time you should actually override __iadd__ is for mutable objects, in which case it should look more like
class Vector2D:
def __iadd__(self, other)
for i, x in enumerate(other):
self[i] += x
return self
Well, strictly that's not OK either, since operators shouldn't be duck-typed. Instead you should do
class Vector2D:
def __iadd__(self, other)
if not isinstance(other, Vector2D):
return NotImplemented
for i, x in enumerate(other):
self[i] += x
return self