How to Use Dataclass Methods in Python

The dataclasses module in Python provides a convenient way to define classes with a minimal amount of boilerplate. By adding the @dataclass decorator to a class, Python generates several default methods automatically. In this practical article, we will have a deep dive into these auto-generated methods and learn how to customize them by specifying custom implementations.

Default Dataclass Methods

The table below describes the default dataclass methods:

Customizing Dataclass Methods

Dataclasses also provide the ability to customize these default methods by specifying custom implementations. To do so, you can define a method with the same name as the default method in your class. For example, to customize (override) the __repr__() method, you could define a method like this:

from dataclasses import dataclass

@dataclass
class MyClass:
    x: int
    y: int

    def __repr__(self):
        return f'Hello there, MyClass(x={self.x}, y={self.y})'

my_class = MyClass(1, 2)
print(my_class)

Output:

Hello there, MyClass(x=1, y=2)

This custom implementation of __repr__() returns a greeting and a string representation of the instance that includes the values of its x and y attributes.

One More Example

This example defines a class named User with a custom equality comparison (override the __eq__() method):

from dataclasses import dataclass

@dataclass
class User:
    name: str
    age: int

    # Compare two users by their age only
    def __eq__(self, other):
        if isinstance(other, User):
            return self.age == other.age
        return False

u1 = User("John", 20)
u2 = User("Jane", 20)
u3 = User("Jack", 30)

print(u1 == u2) 
print(u1 == u3)

Output:

True
False

That’s it. Happy coding!