What does other mean in this code??

Question

class Vector2D:
def __init__(self, x, y):
self.x = x
self.y = y
def __add__(self, other):
return Vector2D(self.x + other.x, self.y + other.y)

first = Vector2D(5, 7)
second = Vector2D(3, 9)
result = first + second
print(result.x)
print(result.y)

Im totally confused. Does "other" mean all other classes?

Answer 1

other means other object of class Vector2D
you can't use + between classes
result = first + second
correct using is:
result = first.__add__(second)
in this case in function __add__ other.x means second.x

Answer 2

nope, other is object of any class. see this example http://code.sololearn.com/cdThe2gTZ3WT . note that the code would break if you called a + 3 . since 3 is int which does not have val attribute.

Answer 3

oh, so you mean when there are more classes like vector 3D which has three objects, "other" will be any other objects including all three objects of Vector3D, right?

Answer 4

so other means all other objects of Vector2D??

Answer 5

yes, other is an instance of any other class or built in type, so if that class does not have x and y attributes, you will get exception. you can implement your __add__ method for only specific classes by checking class of other with isinstance. more about it here http://jcalderone.livejournal.com/32837.html

Answer 6

hey but it worked same when i used "+" instead of __add__
is there any problem when using "+" instead of __add__?

Answer 7

>>>so other means all other objects of Vector2D??
yes.

Answer 8

Hi Jason,
You are right. It's very interesting - Python can search for built-in function using function name.
I learned it just now.
http://www.python-course.eu/python3_magic_methods.php

Answer 9

so if you know that first + second means first.__add__(second)
You can understand very easy that in __add__(self, other) other it's your second class

Answer 10

Thank you guys ;)