All notable changes to this project will be documented in this file. Versions follow Semantic Versioning (<major>.<minor>.<patch>). Backward incompatible (breaking) changes will only be introduced in major versions with advance notice in the Deprecated section of releases.

The semantic versioning only considers the public API as described in API Reference. Components not mentioned in API Reference or different import paths are considered internals and can change in minor and patch releases.

v4.16.0 (2022-10-28)


  • Type Any now parses and instantiates classes when given dict that follows subclass specification pytorch-lightning#15115.

  • Signature methods now accept skipping a number of positionals.

  • Callable type hint with return type a class can now be given a subclass which produces a callable that returns an instance of the class.

  • Support for Python 3.11.


  • Fail to import on Python 3.7 when typing_extensions not installed #178.

  • Crashing when using set typehint with specified dtype #183.


  • Using set_defaults on a config argument raises error and suggests to use default_config_files pytorch-lightning#15174.

  • Trying to add a second config argument to a single parser raises an exception #169.

v4.15.2 (2022-10-20)


  • Regression introduced in 6e7ae6d that produced cryptic error message when an invalid argument given #172.

  • default_env not forwarded to subcommand parsers, causing environment variable names to not be shown in subcommand help pytorch-lightning#12790.

  • Cannot override Callable init_args without passing the class_path #174.

  • Positional subclass type incorrectly adds subclass help as positional.

  • Order of types in Union not being considered.

  • str type fails to parse values of the form ^\w+: *.

  • parse_object does not consider given namespace for previous class_path values.

v4.15.1 (2022-10-07)


  • compute_fn of an argument link applied on parse not given subclass default init_args when loading from config.

  • Subclass --*.help option not available when type is a Union mixed with not subclass types.

  • Override of dict_kwargs items from command line not working.

  • Multiple subclass init_args given through command line not being considered pytorch-lightning#15007.

  • Union types required all subtypes to be supported when expected to be at least one subtype supported #168.

v4.15.0 (2022-09-27)


  • set_defaults now supports subclass by name and normalization of import path.


  • Loop variable capture bug pointed out by

  • Issue with discard init_args when class_path not a subclass.

  • No error shown when arguments given to class group that does not accept arguments #161.

  • Incorrect replacement of **kwargs when *args present in parameter resolver.

  • Override of class_path not discarding init_args when loading from config file.

  • Invalid values given to the compute_fn of a argument link applied on parse without showing an understandable error message.


  • Now UUID and timedelta types are registered on first use to avoid possibly unused imports.

  • json/yaml dump sort now defaults to false for all python implementations.

  • add_class_arguments will not add config load option if no added arguments.

v4.14.1 (2022-09-26)


  • Making import_docstring_parse a deprecated function only for pytorch-lightning backward compatibility.

v4.14.0 (2022-09-14)


  • Support for os.PathLike as typehint #159.

  • Also show known subclasses in help for Type[<type>].

  • Support for attribute docstrings #150.

  • Way to configure parsing docstrings with a single style.


  • Subclass nested argument incorrectly loaded as subclass config #159.

  • Append to list not working for default_config_files in subcommands #157.

v4.13.3 (2022-09-06)


  • Failure to parse when subcommand has no options #158.

  • Optional packages being imported even though not used.

  • Append to list not working for default_config_files #157.

v4.13.2 (2022-08-31)


  • Failure to print help when object used as type hint.

  • Failure to parse init args when type hint is union of str and class.

  • Handle change of non-existent file exception type in latest fsspec version.

v4.13.1 (2022-08-05)


  • Regression that caused parse to fail when providing init_args from command line and the subclass default set as a dict.

v4.13.0 (2022-08-03)


  • Support setting through command line individual dict items without replacing #133 comment.

  • Support super() with non-immediate method resolution order parameter #153.


  • Mypy fails to find jsonargparse type hints #151.

  • For multiple dict_kwargs command line arguments only the last one was kept.

  • Positional list with subtype causing crash #154.

v4.12.0 (2022-07-22)


  • Instantiation links now support multiple sources.

  • AST resolver now supports cls() class instantiation in classmethod #146.

  • AST resolver now supports pop and get from **kwargs.


  • file:/// scheme not working in windows #144.

  • Instantiation links with source an entire subclass incorrectly showed --*.help.

  • Ensure AST-based parameter resolver handles value-less type annotations without error #148.

  • Discarding init_args on class_path change not working for Union with mixed non-subclass types.

  • In some cases debug logs not shown even though JSONARGPARSE_DEBUG set.


  • Instantiation links with source an entire class no longer requires to have a compute function.

  • Instantiation links no longer restricted to first nesting level.

  • AST parameter resolver now only logs debug messages instead of failing #146.

  • Documented AST resolver support for **kwargs use in property.

v4.11.0 (2022-07-12)


  • env_prefix property now also accepts boolean. If set to False, no prefix is used for environment variable names #145.

  • link_arguments support target being an entire subclass object lightning#13539.


  • Method resolution order not working correctly in parameter resolvers #143.


  • env_prefix property will no longer accept None in v5.0.0.

v4.10.2 (2022-07-01)


  • AST resolver fails for self._kwargs assign when a type hint is added.

v4.10.1 (2022-06-29)


  • “Component not supported” crash instead of no parameters #141.

  • Default from default_config_files not shown in help when argument has no default.

  • Only init_args in later config overwrites instead of updates #142.

v4.10.0 (2022-06-21)


  • Signature parameters resolved by inspecting the source code with ASTs pytorch-lightning#11653.

  • Support init args for unresolved parameters in subclasses #114.

  • Allow providing a config with init_args but no class_path #113.


  • dump with skip_default=True not working for subclasses without init_args and when a default value requires serializing.

  • JSONARGPARSE_DEFAULT_ENV should have precedence over given value.

  • Giving an invalid class path and then init args would print a misleading error message about the init arg instead of the class.

  • In some cases print_config could output invalid values. Now a lenient check is done while dumping.

  • Resolved some issues related to the logger property and reconplogger.

  • Single dash '-' incorrectly parsed as [None].


  • dataclasses no longer an optional, now an install require on python 3.6.

  • Parameters of type POSITIONAL_OR_KEYWORD now considered KEYWORD #98.

  • Some refactoring mostly related but not limited to the new AST support.

  • JSONARGPARSE_DEBUG now also sets the reconplogger level to DEBUG.

  • Renamed the test files to follow the more standard test_*.py pattern.

  • Now bool(Namespace()) evaluates to False.

  • When a class_path is overridden, now only the config values that the new subclass doesn’t accept are discarded.


  • logger property will no longer accept None in v5.0.0.

v4.9.0 (2022-06-01)


  • ActionsContainer not calling LoggerProperty.__init__.

  • For type Union[type, List[type] when previous value is None then --arg+=elem should result in a list with single element.


  • Literal options now shown in metavar like choices #106.

  • tuple metavar now shown as [ITEM,...].

  • Required arguments with None default now shown without brackets in usage.

  • Improved description of --print_config in help.

v4.8.0 (2022-05-26)


  • Support append to lists both from command line and config file #85.

  • New register_unresolvable_import_paths function to allow getting the import paths of objects that don’t have a proper __module__ attribute pytorch-lightning#13092.

  • New unit test for merge of config file init_args when class_path does not change #89.


  • Replaced custom pre-commit script with a .pre-commit-config.yaml file.

  • All warnings are now caught in unit tests.

  • Moved return_parser tests to deprecated tests module.

v4.7.3 (2022-05-10)


  • sub_add_kwargs not propagated for parameters of final classes.

  • New union syntax not working #136.

v4.7.2 (2022-04-29)


  • Make import_docstring_parse backward compatible to support released versions of LightningCLI pytorch-lightning#12918.

v4.7.1 (2022-04-26)


v4.7.0 (2022-04-20)


  • Failing to parse strings that look like timestamps #135.

  • Correctly consider nested mapping type without args as supported.

  • New registered types incorrectly considered as class type.


  • Final classes now added as group of actions instead of one typehint action.

  • @final decorator now an import from typing_extensions if available.

  • Exporting ActionsContainer to show respective methods in documentation.

  • Raise ValueError when logger property given dict with unexpected key.

v4.6.0 (2022-04-11)


  • Dump option to exclude entries whose value is the same as the default #91.

  • Support specifying class_path only by name for known subclasses #84.

  • add_argument with subclass type now also adds --*.help option.

  • Support shorter subclass command line arguments by not requiring to have .init_args..

  • Support for Literal backport from typing_extensions on python 3.7.

  • Support nested subclass --*.help CLASS options.


  • class_path’s on parse are now normalized to shortest form.

v4.5.0 (2022-03-29)


  • capture_parser function to get the parser object from a cli function.

  • dump_header property to set header for yaml/jsonnet dumpers #79.

  • Callable type now supports callable classes #110.


  • Bug in check for class_path, init_args dicts.

  • Module mocks in


  • Moved argcomplete code from core to optionals module.

  • Callable no longer a simple registered type.

  • Import paths are now serialized as its shortest form.

  • Callable default now shown in help as full import path.

  • Moved typehint code from core to typehint module.

  • Ignore argument links when source/target subclass does not have parameter #129.

  • Swapped order of argument links in help to source --> target.


  • CLI’s return_parser parameter will be removed in v5.0.0.

v4.4.0 (2022-03-18)


  • Environment variables to enable features without code change:
    • JSONARGPARSE_DEFAULT_ENV to enable environment variable parsing.

    • JSONARGPARSE_DEBUG to print of stack trace on parse failure.



  • Use yaml.CSafeLoader for yaml loading if available.

v4.3.1 (2022-03-01)


  • Incorrect use of yaml_load with jsonnet parser mode #125.

  • Load of subconfigs not correctly changing working directory #125.

  • Regression introduced in commit 97e4567 fixed and updated unit test to prevent it #128.

  • --print_config fails for subcommands when default_env=True #126.

v4.3.0 (2022-02-22)


  • Subcommands now also consider parent parser’s default_config_files pytorch-lightning#11622.

  • Automatically added group config load options are now shown in the help #121.


  • Dumper for jsonnet should be json instead of yaml #123.

  • jsonnet import path not working correctly #122.


v4.2.0 (2022-02-09)


  • object_path_serializer and import_object support class methods #99.

  • parser_mode is now a property that when set, propagates to subparsers.

  • add_method_arguments also add parameters from same method of parent classes when *args or **kwargs present.


  • Optional Enum types incorrectly adding a --*.help argument.

  • Specific errors for invalid value for --*.help class_path.

v4.1.4 (2022-01-26)


  • Subcommand parsers not using the parent’s parser_mode.

  • Namespace __setitem__ failing when key corresponds to a nested dict.

v4.1.3 (2022-01-24)


  • String within curly braces parsed as dict due to yaml spec implicit values.

v4.1.2 (2022-01-20)


  • Namespace TypeError with non-str inputs #116.

  • print_config failing on subclass with required arguments #115.

v4.1.1 (2022-01-13)


v4.1.0 (2021-12-06)


  • set_loader function to allow replacing default yaml loader or adding a new parser mode.

  • set_dumper function to allow changing default dump formats or adding new named dump formats.

  • parser_mode='omegaconf' option to use OmegaConf as a loader, adding variable interpolation support.


  • class_from_function missing dereference of string return type #105.

v4.0.4 (2021-11-29)


  • Linking of attributes applied on instantiation ignoring compute_fn.

  • Show full class paths in --*.help description to avoid misinterpretation.

  • --*.help action failing when fail_untyped and/or skip is required. #101.

  • Raise exception if lazy_instance called with invalid lazy_kwargs.

  • Only add subclass defaults on defaults merging #103.

  • Strict type and required only on final config check #31.

  • instantiate_classes failing for type hints with nargs='+'.

  • Useful error message when init_args value invalid.

  • Specific error message when subclass dict has unexpected keys.

  • Removed unnecessary recursive calls causing slow parsing.

v4.0.3 (2021-11-23)


  • Command line parsing of init_args failing with subclasses without a default.

  • get_default failing when destination key does not exist in default config file.

  • Fixed issue with empty help string caused by a change in argparse python 3.9.

v4.0.2 (2021-11-22)


  • Specifying init_args from the command line resulting in empty namespace when no prior class_path given.

  • Fixed command line parsing of class_path and init_args options within subcommand.

  • lazy_instance of final class leading to incorrect default that includes class_path and init_args.

  • add_subclass_arguments not accepting a default keyword parameter.

  • Make it possible to disable deprecation warnings.

v4.0.0 (2021-11-16)


  • New Namespace class that natively supports nesting and avoids flat/dict conversions.

  • python 3.10 is now supported and included in circleci tests.

  • Readme changed to use doctest and tests are run in github workflow.

  • More type hints throughout the code base.

  • New unit tests to increase coverage.

  • Include dataclasses extras require for tox testing.

  • Automatic namespace to dict for link based on target or compute_fn type.


  • Fixed issues related to conflict namespace base.

  • Fixed the parsing of Dict[int, str] type #87.

  • Fixed inner relative config with for commented tests for parse_env and CLI.

  • init_args from default_config_files not discarded when class_path is overridden.

  • Problems with class instantiation for parameters of final classes.

  • dump/save not removing linked target keys.

  • lazy_instance not working with torch.nn.Module #96.


  • General refactoring and cleanup related to new Namespace class.

  • Parsed values from ActionJsonSchema/ActionJsonnet are now dict instead of Namespace.

  • Removed support for python 3.5 and related code cleanup.

  • contextvars package is now an install require for python 3.6.

  • Deprecations are now shown as JsonargparseDeprecationWarning.


  • ArgumentParser’s parse_as_dict option will be removed in v5.0.0.

  • ArgumentParser’s instantiate_subclasses method will be removed in v5.0.0.


  • python 3.5 is no longer supported.

v3.19.4 (2021-10-04)


  • self.logger undefined on SignatureArguments #92.

  • Fix linking for deep targets #75.

  • Fix import_object failing with “not enough values to unpack” #94.

  • Yaml representer error when dumping unregistered default path type.

v3.19.3 (2021-09-16)


  • add_subclass_arguments with required=False failing on instantiation #83.

v3.19.2 (2021-09-09)


  • add_subclass_arguments with required=False failing when not given #83.

v3.19.1 (2021-09-03)


v3.19.0 (2021-08-27)


  • save now supports saving to an fsspec path #86.


  • Multifile save not working correctly for subclasses #63.

  • link_arguments not working for subcommands #82.


  • Multiple subcommand settings without explicit subcommand is now a warning instead of exception.

v3.18.0 (2021-08-18)


  • Support for parsing Mapping and MutableMapping types.

  • Support for parsing frozenset, MutableSequence and MutableSet types.


  • Don’t discard init_args with non-changing --*.class_path argument.

  • Don’t ignore KeyError in call to instantiate_classes #81.

  • Optional subcommands fail with a KeyError #68.

  • Conflicting namespace for subclass key in subcommand.

  • instantiate_classes not working for subcommand keys #70.

  • Proper file not found message from _ActionConfigLoad #64.

  • parse_path not parsing inner config files.


  • Docstrings no longer supported for python 3.5.

  • Show warning when --*.class_path discards previous init_args.

  • Trigger error when parse_args called with non-string value.

  • ActionParser accepts both title and help, title having preference.

  • Multiple subcommand settings allowed if explicit subcommand given.

v3.17.0 (2021-07-19)


  • datetime.timedelta now supported as a type.

  • New function class_from_function to add signature of functions that return an instantiated class.


  • --*.init_args.* causing crash when overriding value from config file.

v3.16.1 (2021-07-13)


  • Signature functions not working for classes implemented with __new__.

  • instantiate_classes failing when keys not present in config object.

v3.16.0 (2021-07-05)


  • lazy_instance function for serializable class type defaults.

  • Support for parsing multiple matched default config files #58.


  • --*.class_path and --*.init_args.* arguments not being parsed.

  • --help broken when default_config_files fail to parse #60.

  • Pattern in default_config_files not using sort.

v3.15.0 (2021-06-22)


  • Decorator for final classes and an is_final_class function to test it.

  • Support for final classes as type hint.

  • add_subclass_arguments now supports multiple classes given as tuple.

  • add_subclass_arguments now supports the instantiate parameter.


  • Parsing of relative paths inside inner configs for type hint actions.

v3.14.0 (2021-06-08)


  • Method instantiate_classes that instantiates subclasses and class groups.

  • Support for link_arguments that are applied on instantiation.

  • Method add_subclass_arguments now supports skipping of arguments.

  • Added support for Type in type hints #59.


  • Custom string template to avoid problems with percent symbols in docstrings.

v3.13.1 (2021-06-03)


  • Type hint Any not correctly serializing Enum and registered type values.

v3.13.0 (2021-06-02)


  • Inner config file support for subclass type hints in signatures and CLI #57.

  • Forward fail_untyped setting to nested subclass type hints.


  • With fail_untyped=True use type from default value instead of Any.

  • Registered types and typing types incorrectly considered subclass types.


  • Better structure of type hint error messages to ease understanding.

v3.12.1 (2021-05-19)


  • --print_config can now be given before other arguments without value.

  • Fixed conversion of flat namespace to dict when there is a nested empty namespace.

  • Fixed issue with get_defaults with default config file and parse_as_dict=False.

  • Fixed bug in save which failed when there was an int key.


  • --print_config now only receives a value with = syntax.

  • add_{class,method,function,dataclass}_arguments now return a list of added arguments.

v3.12.0 (2021-05-13)


  • Path support for fsspec file systems using the ‘s’ mode flag.

  • set_config_read_mode function that can enable fsspec for config reading.

  • Option for print_config and dump with help as yaml comments.


  • print_config only added to parsers when ActionConfigFile is added.


  • set_url_support functionality now should be done with set_config_read_mode.

v3.11.2 (2021-05-03)


  • Link argument arrow <= can be confused as less or equal, changed to <--.

v3.11.1 (2021-04-30)


  • add_dataclass_arguments not making parameters without default as required #54.

  • Removed from signature add methods required option included by mistake.

v3.11.0 (2021-04-27)


  • CLI now has --config options at subcommand and subsubcommand levels.

  • CLI now adds subcommands with help string taken from docstrings.

  • print_config at subcommand level for global config with implicit subcommands.

  • New Path_drw predefined type.

  • Type hint arguments now support nargs='?'.

  • Signature methods can now skip arguments within init_args of subclasses.


  • Removed skip_check from ActionPathList which was never implemented.


  • ActionPath should no longer be used, instead paths are given as type.


  • Actions not being applied for subsubcommand values.

  • handle_subcommands not correctly inferring subsubcommand.

v3.10.1 (2021-04-24)


  • fail_untyped now adds untyped parameters as type Any and if no default then default set to None.


  • --*.help option being added for non-subclass types.

  • Iterable and Sequence types not working for python>=3.7 #53.

v3.10.0 (2021-04-19)


  • set_defaults method now works for arguments within subcommands.

  • CLI set_defaults option to allow overriding of defaults.

  • CLI return_parser option to ease inclusion in documentation.

  • save_path_content attribute to save paths content on config save.

  • New link_arguments method to derive an argument value from others.

  • print_config now includes subclass init_args if class_path given.

  • Subclass type hints now also have a --*.help option.


  • Signature parameters whose name starts with “_” are skipped.

  • The repr of Path now has the form Path_{mode}(.


  • CLI now does instantiate_subclasses before running.

v3.9.0 (2021-04-09)


  • New method add_dataclass_arguments.

  • Dataclasses are now supported as a type.

  • New predefined type Path_dc.

  • Experimental Callable type support.

  • Signature methods with nested key can be made required.

  • Support for Literal types.

  • New option in signatures methods to not fail for untyped required.


  • Generation of yaml now uses internally pyyaml’s safe_dump.

  • New cleaner implementation for type hints support.

  • Moved deprecated code to a module specific for this.

  • Path types repr now has format Path(rel[, cwd=dir]).

  • instantiate_subclasses now always returns a dict.


  • ActionEnum should no longer be used, instead enums are given as type.


  • Deserialization of types not being done for nested config files.

v3.8.1 (2021-03-22)


  • Help fails saying required args missing if default config file exists #48.

  • ActionYesNo arguments failing when parsing from environment variable #49.

v3.8.0 (2021-03-22)


  • Path class now supports home prefix ‘~’ #45.

  • yaml/json dump kwargs can now be changed via attributes dump_yaml_kwargs and dump_json_kwargs.


  • Now by default dump/save/print_config preserve the add arguments and argument groups order (only CPython>=3.6) #46.

  • ActionParser group title now defaults to None if not given #47.

  • Add argument with type Enum or type hint giving an action now raises error #45.

  • Parser help now also considers default_config_files and shows which config file was loaded #47.

  • get_default method now also considers default_config_files.

  • get_defaults now raises ParserError if default config file not valid.


  • default_config_files property not removing help group when setting None.

v3.7.0 (2021-03-17)


  • ActionParser now moves all actions to the parent parser.

  • The help of ActionParser arguments is now shown in the main help #41.


  • Use of required in ActionParser parsers not working #43.

  • Nested options with names including dashes not working #42.

  • DefaultHelpFormatter not properly using env_prefix to show var names.

v3.6.0 (2021-03-08)


  • Function to register additional types for use in parsers.

  • Type hint support for complex and UUID classes.


  • PositiveInt and NonNegativeInt now gives error instead of silently truncating when given float.

  • Types created with restricted_number_type and restricted_string_type now share a common TypeCore base class.


  • ActionOperators not give error if type already registered.

  • List[Tuple] types not working correctly.

  • Some nested dicts kept as Namespace by dump.

v3.5.1 (2021-02-26)


  • Parsing of relative paths in default_config_files not working.

  • Description of tuple type in the readme.

v3.5.0 (2021-02-12)


  • Tuples with ellipsis are now supported #40.


  • Using dict as type incorrectly considered as class requiring class_path.

  • Nested tuples were not working correctly #40.

v3.4.1 (2021-02-03)


  • CLI crashed for class method when zero args given after subcommand.

  • Options before subcommand provided in config file gave subcommand not given.

  • Arguments in groups without help not showing required, type and default.

  • Required arguments help incorrectly showed null default value.

  • Various improvements and fixes to the readme.

v3.4.0 (2021-02-01)


  • Save with multifile=True now creates original jsonnet file for ActionJsonnet.

  • default_config_files is now a property of parser objects.

  • Table in readme to ease understanding of extras requires for optional features #38.


  • Save with multifile=True uses file extension to choose json or yaml format.


  • Better exception message when using ActionJsonSchema and jsonschema not installed #38.

v3.3.2 (2021-01-22)


  • Changed actions so that keyword arguments are visible in API.

  • Fixed save method short description which was copy paste of dump.

  • Added missing docstring in instantiate_subclasses method.

  • Fixed crash when using --help and ActionConfigFile not given help string.

  • Standardized capitalization and punctuation of: help, config, version.

v3.3.1 (2021-01-08)


  • instantiate_subclasses work properly when init_args not present.

  • Addressed a couple of issues pointed out by sonarcloud.

v3.3.0 (2021-01-08)


  • New add_subclass_arguments method to add as type with a specific help option.

v3.2.1 (2020-12-30)


  • Automatic Optional for arguments with default None #30.

  • CLI now supports running methods from classes.

  • Signature arguments can now be loaded from independent config files #32.

  • add_argument now supports enable_path for type based on jsonschema.

  • print_config can now be given as value skip_null to exclude null entries.


  • Improved description of parser used as standalone and for ActionParser #34.

  • Removed __cwd__ and top level __path__ that were not needed.


  • ActionYesNo argument in help the type is now bool.

  • Correctly skip self in add_method_arguments for inherited methods.

  • Prevent failure of dump in cleanup_actions due to new _ActionConfigLoad.

  • Prevent failure in save_paths for dict with int keys.

  • Avoid duplicate config check failure message with subcommands.

v3.1.0 (2020-12-09)


  • Support for multiple levels of subcommands #29.

  • Default description of subcommands explaining use of --help.

v3.0.1 (2020-12-02)


  • add_class_arguments incorrectly added arguments from __call__ instead of __init__ for callable classes.

v3.0.0 (2020-12-01)


  • Functions to add arguments from classes, methods and functions.

  • CLI function that allows creating a line command line interface with a single line of code inspired by Fire.

  • Typing module that includes predefined types and type generator functions for paths and restricted numbers/strings.

  • Extended support to add_argument type to allow complex type hints.

  • Parsers now include --print_config option to dump defaults.

  • Support argcomplete for tab completion of arguments.


  • ArgumentParsers by default now use as error_handler the usage_and_exit_error_handler.

  • error_handler and formatter_class no longer accept as value a string.

  • Changed SimpleNamespace to Namespace to avoid unnecessary differences with argparse.


  • ActionOperators should no longer be used, the new alternative is restricted number types.


The change log was introduced in v3.0.0. For details of the changes for previous versions take a look at the git log. It more or less reads like a change log.