How to support comparison `<` and `>` operators for a Python class?

Question

I have this code:

class Point:
    def __init__(self, x, y, z):
        self.x = x
        self.y = y
        self.z = z
    
    def __add__(self, other):
        return Point((self.x ** 2) + (other.x ** 2), (self.y ** 2) + (other.y ** 2), (self.z ** 2) + (other.z ** 2))

    def __str__(self):
        return f'x: {self.x}, y: {self.y}, z: {self.z}'

pt1 = Point(3, 4, -5)
pt2 = Point(-4, 1, 3)

pt3 = pt1 + pt2

print(pt1 == pt2)

Now I want to change == in the last line to > or <, but this error was raised:

TypeError: '>' not supported between instances of 'Point' and 'Point'

score 2 · Answer 1 · edited May 08 '22 at 08:34

These are the so-called "rich comparison" methods.

object.__lt__(self, other)
object.__le__(self, other)
object.__eq__(self, other)
object.__ne__(self, other)
object.__gt__(self, other)
object.__ge__(self, other)

The correspondence between operator symbols and method names is as follows:

x<y calls x.__lt__(y)
x<=y calls x.__le__(y)
x==y calls x.__eq__(y)
x!=y calls x.__ne__(y)
x>y calls x.__gt__(y)
x>=y calls x.__ge__(y).

Reference

docs.python/datamodel

How to support comparison `<` and `>` operators for a Python class?

1 Answers1

Reference