Pydantic

Why Pydantic exists as a boundary-parsing layer rather than a general validation library, how pydantic-core's compiled schemas make that parsing fast, and why model_dump, model_dump_json, and model_json_schema answer three different questions - the mental model behind every other page in this section.

Models, fields, and automatic validation.

Constrained types, defaults, and aliases.

Field/model validators and computed fields.

`model_dump`, JSON schema, and custom serializers.

`pydantic-settings` for env/config.

Choosing a modeling tool.

Validate at the boundary, trust inside.