246 – Custom hashable objects

An object can be made hashable if you implement the dunder method __hash__. When you do, a common way to implement __hash__ is by building a tuple with the object’s attributes and then hashing that:

class Person:
    def __init__(self, name, age):
        self.name = name
        self.age = age

    def __hash__(self):
        return hash( (self.name, self.age) )
        
    def __eq__(self):
        ...

Whenever you implement __hash__, make sure to implement __eq__ as well, otherwise you’ll get inconsistent behaviour.