fastapi 0.100.0

on Python PyPI

✨ Support for Pydantic v2 ✨

Pydantic version 2 has the core re-written in Rust and includes a lot of improvements and features, for example:

• Improved correctness in corner cases.
• Safer types.
• Better performance and less energy consumption.
• Better extensibility.
• etc.

...all this while keeping the same Python API. In most of the cases, for simple models, you can simply upgrade the Pydantic version and get all the benefits. 🚀

In some cases, for pure data validation and processing, you can get performance improvements of 20x or more. This means 2,000% or more. 🤯

When you use FastAPI, there's a lot more going on, processing the request and response, handling dependencies, executing your own code, and particularly, waiting for the network. But you will probably still get some nice performance improvements just from the upgrade.

The focus of this release is compatibility with Pydantic v1 and v2, to make sure your current apps keep working. Later there will be more focus on refactors, correctness, code improvements, and then performance improvements. Some third-party early beta testers that ran benchmarks on the beta releases of FastAPI reported improvements of 2x - 3x. Which is not bad for just doing pip install --upgrade fastapi pydantic. This was not an official benchmark and I didn't check it myself, but it's a good sign.

Migration

Check out the Pydantic migration guide.

For the things that need changes in your Pydantic models, the Pydantic team built bump-pydantic.

A command line tool that will process your code and update most of the things automatically for you. Make sure you have your code in git first, and review each of the changes to make sure everything is correct before committing the changes.

Pydantic v1

This version of FastAPI still supports Pydantic v1. And although Pydantic v1 will be deprecated at some point, ti will still be supported for a while.

This means that you can install the new Pydantic v2, and if something fails, you can install Pydantic v1 while you fix any problems you might have, but having the latest FastAPI.

There are tests for both Pydantic v1 and v2, and test coverage is kept at 100%.

Changes

• There are new parameter fields supported by Pydantic Field() for:

  • Path()
  • Query()
  • Header()
  • Cookie()
  • Body()
  • Form()
  • File()

• The new parameter fields are:

  • default_factory
  • alias_priority
  • validation_alias
  • serialization_alias
  • discriminator
  • strict
  • multiple_of
  • allow_inf_nan
  • max_digits
  • decimal_places
  • json_schema_extra

...you can read about them in the Pydantic docs.

• The parameter regex has been deprecated and replaced by pattern.

  • You can read more about it in the docs for Query Parameters and String Validations: Add regular expressions.

• New Pydantic models use an improved and simplified attribute model_config that takes a simple dict instead of an internal class Config for their configuration.

  • You can read more about it in the docs for Declare Request Example Data.

• The attribute schema_extra for the internal class Config has been replaced by the key json_schema_extra in the new model_config dict.

  • You can read more about it in the docs for Declare Request Example Data.

• When you install "fastapi[all]" it now also includes:

  • pydantic-settings - for settings management.
  • pydantic-extra-types - for extra types to be used with Pydantic.

• Now Pydantic Settings is an additional optional package (included in "fastapi[all]"). To use settings you should now import from pydantic_settings import BaseSettings instead of importing from pydantic directly.

  • You can read more about it in the docs for Settings and Environment Variables.

• PR #9816 by @tiangolo, included all the work done (in multiple PRs) on the beta branch (main-pv2).