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How can initialization arguments be validated in a Pythonic manner using Python dataclass?

asked 2021-04-28 11:00:00 +0000

lalupa gravatar image

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answered 2021-09-02 15:00:00 +0000

plato gravatar image

Initialization arguments can be validated using Python dataclass by defining a method called __post_init__ in the dataclass. This method is called after the instance has been initialized with the given arguments and can be used to validate those arguments.

Here's an example:

from dataclasses import dataclass

class Person:
    name: str
    age: int

    def __post_init__(self):
        if self.age < 0:
            raise ValueError("Age cannot be negative.")

In this example, we define a Person dataclass with two attributes, name and age. We define a __post_init__ method that checks if the age is negative and raises a ValueError if it is.

Now, when we initialize a Person object, the __post_init__ method will be called automatically, and the argument validation will be performed.

p = Person("Alice", 25)  # This works fine
p = Person("John", -10)  # This raises ValueError: Age cannot be negative.

By using __post_init__, we can keep the validation logic inside the dataclass, making our code more organized and Pythonic.

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Asked: 2021-04-28 11:00:00 +0000

Seen: 11 times

Last updated: Sep 02 '21