What are the advanced features of dataclasses in Python?

What are the advanced features of dataclasses in Python?

Dataclasses in Python offer several advanced features like default values, factory functions, and immutability. Would you like to know more about any specific feature?

Can you explain how to use default values in dataclasses?

Sure! You can set default values for fields in a dataclass by assigning them directly in the class definition. For example:

from dataclasses import dataclass

@dataclass
class Person:
    name: str
    age: int = 30  # Default value for age

This way, if you create a Person without specifying an age, it will default to 30.

What about using factory functions for default values?

Great question! You can use field(default_factory=...) to set a default value using a factory function. For instance:

from dataclasses import dataclass, field

@dataclass
class Item:
    name: str
    tags: list = field(default_factory=list)  # Default to an empty list

This ensures that each instance of Item gets its own list.

Are there any features for making dataclasses immutable?

Yes! You can make a dataclass immutable by setting frozen=True in the decorator. This prevents any modification of the instance after it's created. Here's an example:

from dataclasses import dataclass

@dataclass(frozen=True)
class Point:
    x: int
    y: int

Now, trying to change Point.x will raise a FrozenInstanceError.