Changelog

v1.4 (2020-01-24)🔗

  • Breaking Change: alias precedence logic changed so aliases on a field always take priority over an alias from alias_generator to avoid buggy/unexpected behaviour, see here for details, #1178 by @samuelcolvin
  • Add support for unicode and punycode in TLDs, #1182 by @jamescurtin
  • Fix cls argument in validators during assignment, #1172 by @samuelcolvin
  • completing Luhn algorithm for PaymentCardNumber, #1166 by @cuencandres
  • add support for generics that implement __get_validators__ like a custom data type, #1159 by @tiangolo
  • add support for infinite generators with Iterable, #1152 by @tiangolo
  • fix url_regex to accept schemas with +, - and . after the first character, #1142 by @samuelcolvin
  • move version_info() to version.py, suggest its use in issues, #1138 by @samuelcolvin
  • Improve pydantic import time by roughly 50% by deferring some module loading and regex compilation, #1127 by @samuelcolvin
  • Fix EmailStr and NameEmail to accept instances of themselves in cython, #1126 by @koxudaxi
  • Pass model class to the Config.schema_extra callable, #1125 by @therefromhere
  • Fix regex for username and password in URLs, #1115 by @samuelcolvin
  • Add support for nested generic models, #1104 by @dmontagu
  • add __all__ to __init__.py to prevent "implicit reexport" errors from mypy, #1072 by @samuelcolvin
  • Add support for using "dotenv" files with BaseSettings, #1011 by @acnebs

v1.3 (2019-12-21)🔗

  • Change schema and schema_model to handle dataclasses by using their __pydantic_model__ feature, #792 by @aviramha
  • Added option for root_validator to be skipped if values validation fails using keyword skip_on_failure=True, #1049 by @aviramha
  • Allow Config.schema_extra to be a callable so that the generated schema can be post-processed, #1054 by @selimb
  • Update mypy to version 0.750, #1057 by @dmontagu
  • Trick Cython into allowing str subclassing, #1061 by @skewty
  • Prevent type attributes being added to schema unless the attribute __schema_attributes__ is True, #1064 by @samuelcolvin
  • Change BaseModel.parse_file to use Config.json_loads, #1067 by @kierandarcy
  • Fix for optional Json fields, #1073 by @volker48
  • Change the default number of threads used when compiling with cython to one, allow override via the CYTHON_NTHREADS environment variable, #1074 by @samuelcolvin
  • Run FastAPI tests during Pydantic's CI tests, #1075 by @tiangolo
  • My mypy strictness constraints, and associated tweaks to type annotations, #1077 by @samuelcolvin
  • Add __eq__ to SecretStr and SecretBytes to allow "value equals", #1079 by @sbv-trueenergy
  • Fix schema generation for nested None case, #1088 by @lutostag
  • Consistent checks for sequence like objects, #1090 by @samuelcolvin
  • Fix Config inheritance on BaseSettings when used with env_prefix, #1091 by @samuelcolvin
  • Fix for __modify_schema__ when it conflicted with field_class_to_schema*, #1102 by @samuelcolvin
  • docs: Fix explanation of case sensitive environment variable names when populating BaseSettings subclass attributes, #1105 by @tribals
  • Rename django-rest-framework benchmark in documentation, #1119 by @frankie567

v1.2 (2019-11-28)🔗

  • Possible Breaking Change: Add support for required Optional with name: Optional[AnyType] = Field(...) and refactor ModelField creation to preserve required parameter value, #1031 by @tiangolo; see here for details
  • Add benchmarks for cattrs, #513 by @sebastianmika
  • Add exclude_none option to dict() and friends, #587 by @niknetniko
  • Add benchmarks for valideer, #670 by @gsakkis
  • Add parse_obj_as and parse_file_as functions for ad-hoc parsing of data into arbitrary pydantic-compatible types, #934 by @dmontagu
  • Add allow_reuse argument to validators, thus allowing validator reuse, #940 by @dmontagu
  • Add support for mapping types for custom root models, #958 by @dmontagu
  • Mypy plugin support for dataclasses, #966 by @koxudaxi
  • Add support for dataclasses default factory, #968 by @ahirner
  • Add a ByteSize type for converting byte string (1GB) to plain bytes, #977 by @dgasmith
  • Fix mypy complaint about @root_validator(pre=True), #984 by @samuelcolvin
  • Add manylinux binaries for python 3.8 to pypi, also support manylinux2010, #994 by @samuelcolvin
  • Adds ByteSize conversion to another unit, #995 by @dgasmith
  • Fix __str__ and __repr__ inheritance for models, #1022 by @samuelcolvin
  • add testimonials section to docs, #1025 by @sullivancolin
  • Add support for typing.Literal for Python 3.8, #1026 by @dmontagu

v1.1.1 (2019-11-20)🔗

  • Fix bug where use of complex fields on sub-models could cause fields to be incorrectly configured, #1015 by @samuelcolvin

v1.1 (2019-11-07)🔗

  • Add a mypy plugin for type checking BaseModel.__init__ and more, #722 by @dmontagu
  • Change return type typehint for GenericModel.__class_getitem__ to prevent PyCharm warnings, #936 by @dmontagu
  • Fix usage of Any to allow None, also support TypeVar thus allowing use of un-parameterised collection types e.g. Dict and List, #962 by @samuelcolvin
  • Set FieldInfo on subfields to fix schema generation for complex nested types, #965 by @samuelcolvin

v1.0 (2019-10-23)🔗

  • Breaking Change: deprecate the Model.fields property, use Model.__fields__ instead, #883 by @samuelcolvin
  • Breaking Change: Change the precedence of aliases so child model aliases override parent aliases, including using alias_generator, #904 by @samuelcolvin
  • Breaking change: Rename skip_defaults to exclude_unset, and add ability to exclude actual defaults, #915 by @dmontagu
  • Add **kwargs to pydantic.main.ModelMetaclass.__new__ so __init_subclass__ can take custom parameters on extended BaseModel classes, #867 by @retnikt
  • Fix field of a type that has a default value, #880 by @koxudaxi
  • Use FutureWarning instead of DeprecationWarning when alias instead of env is used for settings models, #881 by @samuelcolvin
  • Fix issue with BaseSettings inheritance and alias getting set to None, #882 by @samuelcolvin
  • Modify __repr__ and __str__ methods to be consistent across all public classes, add __pretty__ to support python-devtools, #884 by @samuelcolvin
  • deprecation warning for case_insensitive on BaseSettings config, #885 by @samuelcolvin
  • For BaseSettings merge environment variables and in-code values recursively, as long as they create a valid object when merged together, to allow splitting init arguments, #888 by @idmitrievsky
  • change secret types example, #890 by @ashears
  • Change the signature of Model.construct() to be more user-friendly, document construct() usage, #898 by @samuelcolvin
  • Add example for the construct() method, #907 by @ashears
  • Improve use of Field constraints on complex types, raise an error if constraints are not enforceable, also support tuples with an ellipsis Tuple[X, ...], Sequence and FrozenSet in schema, #909 by @samuelcolvin
  • update docs for bool missing valid value, #911 by @trim21
  • Better str/repr logic for ModelField, #912 by @samuelcolvin
  • Fix ConstrainedList, update schema generation to reflect min_items and max_items Field() arguments, #917 by @samuelcolvin
  • Allow abstracts sets (eg. dict keys) in the include and exclude arguments of dict(), #921 by @samuelcolvin
  • Fix JSON serialization errors on ValidationError.json() by using pydantic_encoder, #922 by @samuelcolvin
  • Clarify usage of remove_untouched, improve error message for types with no validators, #926 by @retnikt

v1.0b2 (2019-10-07)🔗

  • Mark StrictBool typecheck as bool to allow for default values without mypy errors, #690 by @dmontagu
  • Transfer the documentation build from sphinx to mkdocs, re-write much of the documentation, #856 by @samuelcolvin
  • Add support for custom naming schemes for GenericModel subclasses, #859 by @dmontagu
  • Add if TYPE_CHECKING: to the excluded lines for test coverage, #874 by @dmontagu
  • Rename allow_population_by_alias to allow_population_by_field_name, remove unnecessary warning about it, #875 by @samuelcolvin

v1.0b1 (2019-10-01)🔗

  • Breaking Change: rename Schema to Field, make it a function to placate mypy, #577 by @samuelcolvin
  • Breaking Change: modify parsing behavior for bool, #617 by @dmontagu
  • Breaking Change: get_validators is no longer recognised, use __get_validators__. Config.ignore_extra and Config.allow_extra are no longer recognised, use Config.extra, #720 by @samuelcolvin
  • Breaking Change: modify default config settings for BaseSettings; case_insensitive renamed to case_sensitive, default changed to case_sensitive = False, env_prefix default changed to '' - e.g. no prefix, #721 by @dmontagu
  • Breaking change: Implement root_validator and rename root errors from __obj__ to __root__, #729 by @samuelcolvin
  • Breaking Change: alter the behaviour of dict(model) so that sub-models are nolonger converted to dictionaries, #733 by @samuelcolvin
  • Breaking change: Added initvars support to post_init_post_parse, #748 by @Raphael-C-Almeida
  • Breaking Change: Make BaseModel.json() only serialize the __root__ key for models with custom root, #752 by @dmontagu
  • Breaking Change: complete rewrite of URL parsing logic, #755 by @samuelcolvin
  • Breaking Change: preserve superclass annotations for field-determination when not provided in subclass, #757 by @dmontagu
  • Breaking Change: BaseSettings now uses the special env settings to define which environment variables to read, not aliases, #847 by @samuelcolvin
  • add support for assert statements inside validators, #653 by @abdusco
  • Update documentation to specify the use of pydantic.dataclasses.dataclass and subclassing pydantic.BaseModel, #710 by @maddosaurus
  • Allow custom JSON decoding and encoding via json_loads and json_dumps Config properties, #714 by @samuelcolvin
  • make all annotated fields occur in the order declared, #715 by @dmontagu
  • use pytest to test mypy integration, #735 by @dmontagu
  • add __repr__ method to ErrorWrapper, #738 by @samuelcolvin
  • Added support for FrozenSet members in dataclasses, and a better error when attempting to use types from the typing module that are not supported by Pydantic, #745 by @djpetti
  • add documentation for Pycharm Plugin, #750 by @koxudaxi
  • fix broken examples in the docs, #753 by @dmontagu
  • moving typing related objects into pydantic.typing, #761 by @samuelcolvin
  • Minor performance improvements to ErrorWrapper, ValidationError and datetime parsing, #763 by @samuelcolvin
  • Improvements to datetime/date/time/timedelta types: more descriptive errors, change errors to value_error not type_error, support bytes, #766 by @samuelcolvin
  • fix error messages for Literal types with multiple allowed values, #770 by @dmontagu
  • Improved auto-generated title field in JSON schema by converting underscore to space, #772 by @skewty
  • support mypy --no-implicit-reexport for dataclasses, also respect --no-implicit-reexport in pydantic itself, #783 by @samuelcolvin
  • add the PaymentCardNumber type, #790 by @matin
  • Fix const validations for lists, #794 by @hmvp
  • Set additionalProperties to false in schema for models with extra fields disallowed, #796 by @Code0x58
  • EmailStr validation method now returns local part case-sensitive per RFC 5321, #798 by @henriklindgren
  • Added ability to validate strictness to ConstrainedFloat, ConstrainedInt and ConstrainedStr and added StrictFloat and StrictInt classes, #799 by @DerRidda
  • Improve handling of None and Optional, replace whole with each_item (inverse meaning, default False) on validators, #803 by @samuelcolvin
  • add support for Type[T] type hints, #807 by @timonbimon
  • Performance improvements from removing change_exceptions, change how pydantic error are constructed, #819 by @samuelcolvin
  • Fix the error message arising when a BaseModel-type model field causes a ValidationError during parsing, #820 by @dmontagu
  • allow getter_dict on Config, modify GetterDict to be more like a Mapping object and thus easier to work with, #821 by @samuelcolvin
  • Only check TypeVar param on base GenericModel class, #842 by @zpencerq
  • rename Model._schema_cache -> Model.__schema_cache__, Model._json_encoder -> Model.__json_encoder__, Model._custom_root_type -> Model.__custom_root_type__, #851 by @samuelcolvin

v0.32.2 (2019-08-17)🔗

  • fix __post_init__ usage with dataclass inheritance, fix #739 by @samuelcolvin
  • fix required fields validation on GenericModels classes, #742 by @amitbl
  • fix defining custom Schema on GenericModel fields, #754 by @amitbl

v0.32.1 (2019-08-08)🔗

v0.32 (2019-08-06)🔗

  • add model name to ValidationError error message, #676 by @dmontagu
  • breaking change: remove __getattr__ and rename __values__ to __dict__ on BaseModel, deprecation warning on use __values__ attr, attributes access speed increased up to 14 times, #712 by @MrMrRobat
  • support ForwardRef (without self-referencing annotations) in Python 3.6, #706 by @koxudaxi
  • implement schema_extra in Config sub-class, #663 by @tiangolo

v0.31.1 (2019-07-31)🔗

  • fix json generation for EnumError, #697 by @dmontagu
  • update numerous dependencies

v0.31 (2019-07-24)🔗

v0.30.1 (2019-07-15)🔗

  • fix so nested classes which inherit and change __init__ are correctly processed while still allowing self as a parameter, #644 by @lnaden and @dgasmith

v0.30 (2019-07-07)🔗

v0.29 (2019-06-19)🔗

  • support dataclasses.InitVar, #592 by @pfrederiks
  • Updated documentation to elucidate the usage of Union when defining multiple types under an attribute's annotation and showcase how the type-order can affect marshalling of provided values, #594 by @somada141
  • add conlist type, #583 by @hmvp
  • add support for generics, #595 by @dmontagu

v0.28 (2019-06-06)🔗

v0.27 (2019-05-30)🔗

  • breaking change _pydantic_post_init to execute dataclass' original __post_init__ before validation, #560 by @HeavenVolkoff
  • fix handling of generic types without specified parameters, #550 by @dmontagu
  • breaking change (maybe): this is the first release compiled with cython, see the docs and please submit an issue if you run into problems

v0.27.0a1 (2019-05-26)🔗

  • fix JSON Schema for list, tuple, and set, #540 by @tiangolo
  • compiling with cython, manylinux binaries, some other performance improvements, #548 by @samuelcolvin

v0.26 (2019-05-22)🔗

  • fix to schema generation for IPvAnyAddress, IPvAnyInterface, IPvAnyNetwork #498 by @pilosus
  • fix variable length tuples support, #495 by @pilosus
  • fix return type hint for create_model, #526 by @dmontagu
  • Breaking Change: fix .dict(skip_keys=True) skipping values set via alias (this involves changing validate_model() to always returns Tuple[Dict[str, Any], Set[str], Optional[ValidationError]]), #517 by @sommd
  • fix to schema generation for IPv4Address, IPv6Address, IPv4Interface, IPv6Interface, IPv4Network, IPv6Network #532 by @euri10
  • add Color type, #504 by @pilosus and @samuelcolvin

v0.25 (2019-05-05)🔗

v0.24 (2019-04-23)🔗

v0.23 (2019-04-04)🔗

v0.22 (2019-03-29)🔗

v0.21.0 (2019-03-15)🔗

v0.20.1 (2019-02-26)🔗

v0.20.0 (2019-02-18)🔗

  • fix tests for python 3.8, #396 by @samuelcolvin
  • Adds fields to the dir method for autocompletion in interactive sessions, #398 by @dgasmith
  • support ForwardRef (and therefore from __future__ import annotations) with dataclasses, #397 by @samuelcolvin

v0.20.0a1 (2019-02-13)🔗

  • breaking change (maybe): more sophisticated argument parsing for validators, any subset of values, config and field is now permitted, eg. (cls, value, field), however the variadic key word argument ("**kwargs") must be called kwargs, #388 by @samuelcolvin
  • breaking change: Adds skip_defaults argument to BaseModel.dict() to allow skipping of fields that were not explicitly set, signature of Model.construct() changed, #389 by @dgasmith
  • add py.typed marker file for PEP-561 support, #391 by @je-l
  • Fix extra behaviour for multiple inheritance/mix-ins, #394 by @YaraslauZhylko

v0.19.0 (2019-02-04)🔗

  • Support Callable type hint, fix #279 by @proofit404
  • Fix schema for fields with validator decorator, fix #375 by @tiangolo
  • Add multiple_of constraint to ConstrainedDecimal, ConstrainedFloat, ConstrainedInt and their related types condecimal, confloat, and conint #371, thanks @StephenBrown2
  • Deprecated ignore_extra and allow_extra Config fields in favor of extra, #352 by @liiight
  • Add type annotations to all functions, test fully with mypy, #373 by @samuelcolvin
  • fix for 'missing' error with validate_all or validate_always, #381 by @samuelcolvin
  • Change the second/millisecond watershed for date/datetime parsing to 2e10, #385 by @samuelcolvin

v0.18.2 (2019-01-22)🔗

v0.18.1 (2019-01-17)🔗

  • add ConstrainedBytes and conbytes types, #315 @Gr1N
  • adding MANIFEST.in to include license in package .tar.gz, #358 by @samuelcolvin

v0.18.0 (2019-01-13)🔗

  • breaking change: don't call validators on keys of dictionaries, #254 by @samuelcolvin
  • Fix validators with always=True when the default is None or the type is optional, also prevent whole validators being called for sub-fields, fix #132 by @samuelcolvin
  • improve documentation for settings priority and allow it to be easily changed, #343 by @samuelcolvin
  • fix ignore_extra=False and allow_population_by_alias=True, fix #257 by @samuelcolvin
  • breaking change: Set BaseConfig attributes min_anystr_length and max_anystr_length to None by default, fix #349 in #350 by @tiangolo
  • add support for postponed annotations, #348 by @samuelcolvin

v0.17.0 (2018-12-27)🔗

  • fix schema for timedelta as number, #325 by @tiangolo
  • prevent validators being called repeatedly after inheritance, #327 by @samuelcolvin
  • prevent duplicate validator check in ipython, fix #312 by @samuelcolvin
  • add "Using Pydantic" section to docs, #323 by @tiangolo & #326 by @samuelcolvin
  • fix schema generation for fields annotated as : dict, : list, : tuple and : set, #330 & #335 by @nkonin
  • add support for constrained strings as dict keys in schema, #332 by @tiangolo
  • support for passing Config class in dataclasses decorator, #276 by @jarekkar (breaking change: this supersedes the validate_assignment argument with config)
  • support for nested dataclasses, #334 by @samuelcolvin
  • better errors when getting an ImportError with PyObject, #309 by @samuelcolvin
  • rename get_validators to __get_validators__, deprecation warning on use of old name, #338 by @samuelcolvin
  • support ClassVar by excluding such attributes from fields, #184 by @samuelcolvin

v0.16.1 (2018-12-10)🔗

  • fix create_model to correctly use the passed __config__, #320 by @hugoduncan

v0.16.0 (2018-12-03)🔗

  • breaking change: refactor schema generation to be compatible with JSON Schema and OpenAPI specs, #308 by @tiangolo
  • add schema to schema module to generate top-level schemas from base models, #308 by @tiangolo
  • add additional fields to Schema class to declare validation for str and numeric values, #311 by @tiangolo
  • rename _schema to schema on fields, #318 by @samuelcolvin
  • add case_insensitive option to BaseSettings Config, #277 by @jasonkuhrt

v0.15.0 (2018-11-18)🔗

v0.14.0 (2018-10-02)🔗

v0.13.1 (2018-09-21)🔗

  • fix issue where int_validator doesn't cast a bool to an int #264 by @nphyatt
  • add deep copy support for BaseModel.copy() #249, @gangefors

v0.13.0 (2018-08-25)🔗

  • raise an exception if a field's name shadows an existing BaseModel attribute #242
  • add UrlStr and urlstr types #236
  • timedelta json encoding ISO8601 and total seconds, custom json encoders #247, by @cfkanesan and @samuelcolvin
  • allow timedelta objects as values for properties of type timedelta (matches datetime etc. behavior) #247

v0.12.1 (2018-07-31)🔗

  • fix schema generation for fields defined using typing.Any #237

v0.12.0 (2018-07-31)🔗

  • add by_alias argument in .dict() and .json() model methods #205
  • add Json type support #214
  • support tuples #227
  • major improvements and changes to schema #213

v0.11.2 (2018-07-05)🔗

  • add NewType support #115
  • fix list, set & tuple validation #225
  • separate out validate_model method, allow errors to be returned along with valid values #221

v0.11.1 (2018-07-02)🔗

v0.11.0 (2018-06-28)🔗

  • make list, tuple and set types stricter #86
  • breaking change: remove msgpack parsing #201
  • add FilePath and DirectoryPath types #10
  • model schema generation #190
  • JSON serialisation of models and schemas #133

v0.10.0 (2018-06-11)🔗

  • add Config.allow_population_by_alias #160, thanks @bendemaree
  • breaking change: new errors format #179, thanks @Gr1N
  • breaking change: removed Config.min_number_size and Config.max_number_size #183, thanks @Gr1N
  • breaking change: correct behaviour of lt and gt arguments to conint etc. #188 for the old behaviour use le and ge #194, thanks @jaheba
  • added error context and ability to redefine error message templates using Config.error_msg_templates #183, thanks @Gr1N
  • fix typo in validator exception #150
  • copy defaults to model values, so different models don't share objects #154

v0.9.1 (2018-05-10)🔗

  • allow custom get_field_config on config classes #159
  • add UUID1, UUID3, UUID4 and UUID5 types #167, thanks @Gr1N
  • modify some inconsistent docstrings and annotations #173, thanks @YannLuo
  • fix type annotations for exotic types #171, thanks @Gr1N
  • re-use type validators in exotic types #171
  • scheduled monthly requirements updates #168
  • add Decimal, ConstrainedDecimal and condecimal types #170, thanks @Gr1N

v0.9.0 (2018-04-28)🔗

  • tweak email-validator import error message #145
  • fix parse error of parse_date() and parse_datetime() when input is 0 #144, thanks @YannLuo
  • add Config.anystr_strip_whitespace and strip_whitespace kwarg to constr, by default values is False #163, thanks @Gr1N
  • add ConstrainedFloat, confloat, PositiveFloat and NegativeFloat types #166, thanks @Gr1N

v0.8.0 (2018-03-25)🔗

  • fix type annotation for inherit_config #139
  • breaking change: check for invalid field names in validators #140
  • validate attributes of parent models #141
  • breaking change: email validation now uses email-validator #142

v0.7.1 (2018-02-07)🔗

  • fix bug with create_model modifying the base class

v0.7.0 (2018-02-06)🔗

  • added compatibility with abstract base classes (ABCs) #123
  • add create_model method #113 #125
  • breaking change: rename .config to .__config__ on a model
  • breaking change: remove deprecated .values() on a model, use .dict() instead
  • remove use of OrderedDict and use simple dict #126
  • add Config.use_enum_values #127
  • add wildcard validators of the form @validate('*') #128

v0.6.4 (2018-02-01)🔗

  • allow python date and times objects #122

v0.6.3 (2017-11-26)🔗

  • fix direct install without README.rst present

v0.6.2 (2017-11-13)🔗

  • errors for invalid validator use
  • safer check for complex models in Settings

v0.6.1 (2017-11-08)🔗

  • prevent duplicate validators, #101
  • add always kwarg to validators, #102

v0.6.0 (2017-11-07)🔗

  • assignment validation #94, thanks petroswork!
  • JSON in environment variables for complex types, #96
  • add validator decorators for complex validation, #97
  • depreciate values(...) and replace with .dict(...), #99

v0.5.0 (2017-10-23)🔗

  • add UUID validation #89
  • remove index and track from error object (json) if they're null #90
  • improve the error text when a list is provided rather than a dict #90
  • add benchmarks table to docs #91

v0.4.0 (2017-07-08)🔗

  • show length in string validation error
  • fix aliases in config during inheritance #55
  • simplify error display
  • use unicode ellipsis in truncate
  • add parse_obj, parse_raw and parse_file helper functions #58
  • switch annotation only fields to come first in fields list not last

v0.3.0 (2017-06-21)🔗

  • immutable models via config.allow_mutation = False, associated cleanup and performance improvement #44
  • immutable helper methods construct() and copy() #53
  • allow pickling of models #53
  • setattr is removed as __setattr__ is now intelligent #44
  • raise_exception removed, Models now always raise exceptions #44
  • instance method validators removed
  • django-restful-framework benchmarks added #47
  • fix inheritance bug #49
  • make str type stricter so list, dict etc are not coerced to strings. #52
  • add StrictStr which only always strings as input #52

v0.2.1 (2017-06-07)🔗

  • pypi and travis together messed up the deploy of v0.2 this should fix it

v0.2.0 (2017-06-07)🔗

  • breaking change: values() on a model is now a method not a property, takes include and exclude arguments
  • allow annotation only fields to support mypy
  • add pretty to_string(pretty=True) method for models

v0.1.0 (2017-06-03)🔗

  • add docs
  • add history