Pydantic Validation

In a nutshell, Pydantic is dataclasses with runtime validation. It leverages type hints to understand how validation (and serialization) should be performed. It is mostly useful when dealing with external untrusted data, for example when defining an HTTP API.

It is generally not recommended to use Pydantic to define classes that are instantiated within the user code. By doing so, you will lose flexibility (e.g. can't use types not supported by Pydantic, harder to perform post init changes). It is usually better to use vanilla classes (or standard library dataclasses) in this case, as a static type checker will already catch type mismatches.

Basic usage

Here is a simple example of using a Pydantic model:

from datetime import date

from pydantic import BaseModel, Field