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.

Table Of Contents

1 Default Dataclass Methods

2 Customizing Dataclass Methods

3 One More Example

Default Dataclass Methods

The table below describes the default dataclass methods:

Method	Descript
__init__()	Initializes a new instance of the class.
__repr__()	Returns a string representation of the instance.
__eq__()	Compares two instances for equality.
__ne__()	Compares two instances for inequality.
__lt__()	Compares two instances to determine if one is less than the other.
__le__()	Compares two instances to determine if one is less than or equal to the other.
__gt__()	Compares two instances to determine if one is greater than the other.
__ge__()	Compares two instances to determine if one is greater than or equal to the other.

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: