See Changelog.

Thank you to pydantic's sponsors: @timdrijvers, @BCarley, @chdsbd, @tiangolo, @matin, @linusg, @kevinalh, @jorgecarleitao, @koxudaxi, @primer-api for their kind support.

Highlights

• python 3.9 support, thanks @PrettyWood
• Private model attributes, thanks @MrMrRobat
• "secrets files" support in BaseSettings, thanks @mdgilene
• convert stdlib dataclasses to pydantic dataclasses and use stdlib dataclasses in models, thanks @PrettyWood

Changes

• Breaking Change: remove __field_defaults__, add default_factory support with BaseModel.construct. Use .get_default() method on fields in __fields__ attribute instead, #1732 by @PrettyWood
• Rearrange CI to run linting as a separate job, split install recipes for different tasks, #2020 by @samuelcolvin
• Allows subclasses of generic models to make some, or all, of the superclass's type parameters concrete, while also defining new type parameters in the subclass, #2005 by @choogeboom
• Call validator with the correct values parameter type in BaseModel.__setattr__, when validate_assignment = True in model config, #1999 by @me-ransh
• Force fields.Undefined to be a singleton object, fixing inherited generic model schemas, #1981 by @daviskirk
• Include tests in source distributions, #1976 by @sbraz
• Add ability to use min_length/max_length constraints with secret types, #1974 by @uriyyo
• Also check root_validators when validate_assignment is on, #1971 by @PrettyWood
• Fix const validators not running when custom validators are present, #1957 by @hmvp
• add deque to field types, #1935 by @wozniakty
• add basic support for python 3.9, #1832 by @PrettyWood
• Fix typo in the anchor of exporting_models.md#modelcopy and incorrect description, #1821 by @KimMachineGun
• Added ability for BaseSettings to read "secret files", #1820 by @mdgilene
• add parse_raw_as utility function, #1812 by @PrettyWood
• Support home directory relative paths for dotenv files (e.g. ~/.env), #1803 by @PrettyWood
• Clarify documentation for parse_file to show that the argument should be a file path not a file-like object, #1794 by @mdavis-xyz
• Fix false positive from mypy plugin when a class nested within a BaseModel is named Model, #1770 by @selimb
• add basic support of Pattern type in schema generation, #1767 by @PrettyWood
• Support custom title, description and default in schema of enums, #1748 by @PrettyWood
• Properly represent Literal Enums when use_enum_values is True, #1747 by @noelevans
• Allows timezone information to be added to strings to be formatted as time objects. Permitted formats are Z for UTC or an offset for absolute positive or negative time shifts. Or the timezone data can be omitted, #1744 by @noelevans
• Add stub __init__ with python 3.6 signature for ForwardRef, #1738 by @sirtelemak
• Fix behaviour with forward refs and optional fields in nested models, #1736 by @PrettyWood
• add Enum and IntEnum as valid types for fields, #1735 by @PrettyWood
• Change default value of __module__ argument of create_model from None to 'pydantic.main'. Set reference of created concrete model to it's module to allow pickling (not applied to models created in functions), #1686 by @MrMrRobat
• Add private attributes support, #1679 by @MrMrRobat
• add config to @validate_arguments, #1663 by @samuelcolvin
• Allow descendant Settings models to override env variable names for the fields defined in parent Settings models with env in their Config. Previously only env_prefix configuration option was applicable, #1561 by @ojomio
• Support ref_template when creating schema $refs, #1479 by @kilo59
• Add a __call__ stub to PyObject so that mypy will know that it is callable, #1352 by @brianmaissy
• pydantic.dataclasses.dataclass decorator now supports built-in dataclasses.dataclass. It is hence possible to convert an existing dataclass easily to add pydantic validation. Moreover nested dataclasses are also supported, #744 by @PrettyWood