func += (inout left: Vector2D, right: Vector2D) {
left = left + right
}
http://stackoverflow.com/questions/1047021/overriding-in-pyt...
class Vector2D:
def __iadd__(self, other)
return self + other
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 selfWhat would the rationale be for such a rule?
the docs don't mention anything like that https://docs.python.org/2/library/operator.html and I've never heard it before. In Python, neither integers nor strings are mutable and both support the "x += y" syntax.
The __iadd__ method works the same for both mutable and immutable objects AFAIK
Because __iadd__ automatically delegates to __add__. For immutable objects that's the best you can do, so there's no reason to write both.