What is the difference between pydantic v1 and v2 output model?

Summary

datamodel-code-generator supports Pydantic v1 and v2 as output model type.

Pydantic v2 is a major release with many breaking changes. See the migration guide for more information: https://docs.pydantic.dev/2.0/migration/

What's changes in v2 output?

__root__ field (a.k.a Custom Root Types)

__root__ field (a.k.a Custom Root Types) is removed in pydantic v2. The model is changed to RootModel

pydantic.Field

https://docs.pydantic.dev/2.0/migration/#changes-to-pydanticfield

• const -> removed
• min_items (use min_length instead)
• max_items (use max_length instead)
• unique_items -> removed and the list type will be replaced by typing.Set. this feature is discussed in https://github.com/pydantic/pydantic-core/issues/296
• allow_mutation (use frozen instead)
• regex (use pattern instead)

Model Config

• pydantic.Config -> pydantic.ConfigDict
• allow_mutation —> frozen (inverse value for getting same behavior).
• allow_population_by_field_name → populate_by_name