Force python class to accept only certain attributes

We can force Python classes to accept only certain attributes. We can achieve this using the slots special attribute

class Dog():
    __slots__ = ["name", "age"]
    def __init__(self, name, age):
        self.name = name
        self.age = age

Here, setting __slots__ as ["name", "age"] means that our Dog object can only have these 2 attributes.

dog = Dog("rocky", 5)    # ok
dog.name = "fifi"        # ok
dog.age = 6              # ok
dog.breed = "mongrel"    # error

Here, we get an error when we try to set the breed attribute of the Dog object, as only name and age are allowed based on __slots__. This error won’t happen if we didn’t specifically define the __slots__ attribute.

Via python.plainenglish.io.