cattr package

Subpackages

Submodules

cattr.converters module

class cattr.converters.BaseConverter(dict_factory=<class 'dict'>, unstruct_strat=UnstructureStrategy.AS_DICT, prefer_attrib_converters=False, detailed_validation=True)[source]

Bases: object

Converts between structured and unstructured data.

Parameters
Return type

None

copy(dict_factory=None, unstruct_strat=None, prefer_attrib_converters=None, detailed_validation=None)[source]
Parameters

  • dict_factory (Optional[Callable[[], Any]]) –

  • unstruct_strat (Optional[cattrs.converters.UnstructureStrategy]) –

  • prefer_attrib_converters (Optional[bool]) –

  • detailed_validation (Optional[bool]) –

Return type

cattrs.converters.BaseConverter

detailed_validation
register_structure_hook(cl, func)[source]

Register a primitive-to-class converter function for a type.

The converter function should take two arguments:

  • a Python object to be converted,

  • the type to convert to

and return the instance of the class. The type may seem redundant, but is sometimes needed (for example, when dealing with generic classes).

Parameters

  • cl (Any) –

  • func (Callable[[Any, Type[cattrs.converters.T]], cattrs.converters.T]) –

Return type

None

register_structure_hook_factory(predicate, factory)[source]

Register a hook factory for a given predicate.

A predicate is a function that, given a type, returns whether the factory can produce a hook for that type.

A factory is a callable that, given a type, produces a structuring hook for that type. This structuring hook will be cached.

Parameters

  • predicate (Callable[[Any], bool]) –

  • factory (Callable[[Any], Callable[[Any, Any], Any]]) –

Return type

None

register_structure_hook_func(check_func, func)[source]

Register a class-to-primitive converter function for a class, using a function to check if it’s a match.

Parameters

  • check_func (Callable[[Type[cattrs.converters.T]], bool]) –

  • func (Callable[[Any, Type[cattrs.converters.T]], cattrs.converters.T]) –

Return type

None

register_unstructure_hook(cls, func)[source]

Register a class-to-primitive converter function for a class.

The converter function should take an instance of the class and return its Python equivalent.

Parameters

  • cls (Any) –

  • func (Callable[[Any], Any]) –

Return type

None

register_unstructure_hook_factory(predicate, factory)[source]

Register a hook factory for a given predicate.

A predicate is a function that, given a type, returns whether the factory can produce a hook for that type.

A factory is a callable that, given a type, produces an unstructuring hook for that type. This unstructuring hook will be cached.

Parameters

  • predicate (Callable[[Any], bool]) –

  • factory (Callable[[Any], Callable[[Any], Any]]) –

Return type

None

register_unstructure_hook_func(check_func, func)[source]

Register a class-to-primitive converter function for a class, using a function to check if it’s a match.

Parameters

  • check_func (Callable[[Any], bool]) –

  • func (Callable[[Any], Any]) –

Return type

None

structure(obj, cl)[source]

Convert unstructured Python data structures to structured data.

Parameters

  • obj (Any) –

  • cl (Type[cattrs.converters.T]) –

Return type

cattrs.converters.T

structure_attrs_fromdict(obj, cl)[source]

Instantiate an attrs class from a mapping (dict).

Parameters

  • obj (collections.abc.Mapping[str, Any]) –

  • cl (Type[cattrs.converters.T]) –

Return type

cattrs.converters.T

structure_attrs_fromtuple(obj, cl)[source]

Load an attrs class from a sequence (tuple).

Parameters

  • obj (Tuple[Any, ...]) –

  • cl (Type[cattrs.converters.T]) –

Return type

cattrs.converters.T

property unstruct_strat: cattrs.converters.UnstructureStrategy

The default way of unstructuring attrs classes.

unstructure(obj, unstructure_as=None)[source]
Parameters

  • obj (Any) –

  • unstructure_as (Optional[Any]) –

Return type

Any

unstructure_attrs_asdict(obj)[source]

Our version of attrs.asdict, so we can call back to us.

Parameters

obj (Any) –

Return type

Dict[str, Any]

unstructure_attrs_astuple(obj)[source]

Our version of attrs.astuple, so we can call back to us.

Parameters

obj (Any) –

Return type

Tuple[Any, …]

class cattr.converters.Converter(dict_factory=<class 'dict'>, unstruct_strat=UnstructureStrategy.AS_DICT, omit_if_default=False, forbid_extra_keys=False, type_overrides={}, unstruct_collection_overrides={}, prefer_attrib_converters=False, detailed_validation=True)[source]

Bases: cattrs.converters.BaseConverter

A converter which generates specialized un/structuring functions.

Parameters

  • dict_factory (Callable[[], Any]) –

  • unstruct_strat (cattrs.converters.UnstructureStrategy) –

  • omit_if_default (bool) –

  • forbid_extra_keys (bool) –

  • type_overrides (collections.abc.Mapping[Type, cattrs.gen.AttributeOverride]) –

  • unstruct_collection_overrides (collections.abc.Mapping[Type, Callable]) –

  • prefer_attrib_converters (bool) –

  • detailed_validation (bool) –

copy(dict_factory=None, unstruct_strat=None, omit_if_default=None, forbid_extra_keys=None, type_overrides=None, unstruct_collection_overrides=None, prefer_attrib_converters=None, detailed_validation=None)[source]
Parameters

  • dict_factory (Optional[Callable[[], Any]]) –

  • unstruct_strat (Optional[cattrs.converters.UnstructureStrategy]) –

  • omit_if_default (Optional[bool]) –

  • forbid_extra_keys (Optional[bool]) –

  • type_overrides (Optional[collections.abc.Mapping[Type, cattrs.gen.AttributeOverride]]) –

  • unstruct_collection_overrides (Optional[collections.abc.Mapping[Type, Callable]]) –

  • prefer_attrib_converters (Optional[bool]) –

  • detailed_validation (Optional[bool]) –

Return type

cattrs.converters.Converter

forbid_extra_keys
gen_structure_annotated(type)[source]
gen_structure_attrs_fromdict(cl)[source]
Parameters

cl (Type[cattrs.converters.T]) –

Return type

Callable[[collections.abc.Mapping[str, Any], Any], cattrs.converters.T]

gen_structure_counter(cl)[source]
Parameters

cl (Any) –

Return type

Callable[[Mapping[Any, Any], Any], cattrs.converters.T]

gen_structure_mapping(cl)[source]
Parameters

cl (Any) –

Return type

Callable[[Mapping[Any, Any], Any], cattrs.converters.T]

gen_unstructure_annotated(type)[source]
gen_unstructure_attrs_fromdict(cl)[source]
Parameters

cl (Type[cattrs.converters.T]) –

Return type

Callable[[cattrs.converters.T], Dict[str, Any]]

gen_unstructure_hetero_tuple(cl, unstructure_to=None)[source]
Parameters

  • cl (Any) –

  • unstructure_to (Optional[Any]) –

Return type

Callable[[Tuple[Any, …]], Any]

gen_unstructure_iterable(cl, unstructure_to=None)[source]
Parameters

  • cl (Any) –

  • unstructure_to (Optional[Any]) –

Return type

Callable[[Iterable[Any]], Any]

gen_unstructure_mapping(cl, unstructure_to=None, key_handler=None)[source]
Parameters

  • cl (Any) –

  • unstructure_to (Optional[Any]) –

  • key_handler (Optional[Callable[[Any, Optional[Any]], Any]]) –

Return type

Callable[[Mapping[Any, Any]], Any]

get_structure_newtype(type)[source]
Parameters

type (Type[cattrs.converters.T]) –

Return type

Callable[[Any, Any], cattrs.converters.T]

omit_if_default
type_overrides
cattr.converters.GenConverter

alias of cattrs.converters.Converter

class cattr.converters.UnstructureStrategy(value)[source]

Bases: enum.Enum

attrs classes unstructuring strategies.

AS_DICT = 'asdict'
AS_TUPLE = 'astuple'

cattr.disambiguators module

cattr.disambiguators.create_uniq_field_dis_func(*classes)[source]

Given attr classes, generate a disambiguation function.

The function is based on unique fields.

Parameters

classes (Type[Any]) –

Return type

Callable[[Mapping[Any, Any]], Optional[Type[Any]]]

cattr.dispatch module

class cattr.dispatch.FunctionDispatch(handler_pairs=NOTHING)[source]

Bases: object

FunctionDispatch is similar to functools.singledispatch, but instead dispatches based on functions that take the type of the first argument in the method, and return True or False.

objects that help determine dispatch should be instantiated objects.

Parameters

handler_pairs (list) –

Return type

None

copy_to(other, skip=0)[source]
Parameters
dispatch(typ)[source]

returns the appropriate handler, for the object passed.

get_num_fns()[source]
Return type

int

register(can_handle, func, is_generator=False)[source]
Parameters

can_handle (Callable[[Any], bool]) –

class cattr.dispatch.MultiStrategyDispatch(fallback_func)[source]

Bases: object

MultiStrategyDispatch uses a combination of exact-match dispatch, singledispatch, and FunctionDispatch.

clear_cache()[source]

Clear all caches.

clear_direct()[source]

Clear the direct dispatch.

copy_to(other, skip=0)[source]
Parameters
dispatch
get_num_fns()[source]
Return type

int

register_cls_list(cls_and_handler, direct=False)[source]

Register a class to direct or singledispatch.

Parameters

direct (bool) –

Return type

None

register_func_list(pred_and_handler)[source]

Register a predicate function to determine if the handle should be used for the type.

Parameters

pred_and_handler (List[Union[Tuple[Callable[[Any], bool], Any], Tuple[Callable[[Any], bool], Any, bool]]]) –

cattr.errors module

exception cattr.errors.BaseValidationError(message, excs, cl)[source]

Bases: exceptiongroup.ExceptionGroup

Parameters

cl (Type) –

cl: Type
derive(excs)[source]
exception cattr.errors.ClassValidationError(message, excs, cl)[source]

Bases: cattrs.errors.BaseValidationError

Raised when validating a class if any attributes are invalid.

Parameters

cl (Type) –

exception cattr.errors.ForbiddenExtraKeysError(message, cl, extra_fields)[source]

Bases: Exception

Raised when forbid_extra_keys is activated and such extra keys are detected during structuring.

The attribute extra_fields is a sequence of those extra keys, which were the cause of this error, and cl is the class which was structured with those extra keys.

Parameters

  • message (Optional[str]) –

  • cl (Type) –

  • extra_fields (Set[str]) –

Return type

None

exception cattr.errors.IterableValidationError(message, excs, cl)[source]

Bases: cattrs.errors.BaseValidationError

Raised when structuring an iterable.

Parameters

cl (Type) –

exception cattr.errors.StructureHandlerNotFoundError(message, type_)[source]

Bases: Exception

Error raised when structuring cannot find a handler for converting inputs into type_.

Parameters

  • message (str) –

  • type_ (Type) –

Return type

None

cattr.gen module

class cattr.gen.AttributeOverride(omit_if_default=None, rename=None, omit=False)[source]

Bases: object

Parameters

  • omit_if_default (Optional[bool]) –

  • rename (Optional[str]) –

  • omit (bool) –

Return type

None

omit: bool
omit_if_default: Optional[bool]
rename: Optional[str]
cattr.gen.make_dict_structure_fn(cl, converter, _cattrs_forbid_extra_keys=False, _cattrs_use_linecache=True, _cattrs_prefer_attrib_converters=False, _cattrs_detailed_validation=True, **kwargs)[source]

Generate a specialized dict structuring function for an attrs class.

Parameters

  • cl (Type[cattrs.gen.T]) –

  • converter (BaseConverter) –

  • _cattrs_forbid_extra_keys (bool) –

  • _cattrs_use_linecache (bool) –

  • _cattrs_prefer_attrib_converters (bool) –

  • _cattrs_detailed_validation (bool) –

  • kwargs (cattrs.gen.AttributeOverride) –

Return type

Callable[[Mapping[str, Any], Any], cattrs.gen.T]

cattr.gen.make_dict_unstructure_fn(cl, converter, _cattrs_omit_if_default=False, _cattrs_use_linecache=True, **kwargs)[source]

Generate a specialized dict unstructuring function for an attrs class or a dataclass.

Parameters
Return type

Callable[[cattrs.gen.T], Dict[str, Any]]

cattr.gen.make_hetero_tuple_unstructure_fn(cl, converter, unstructure_to=None)[source]

Generate a specialized unstructure function for a heterogenous tuple.

Parameters

  • cl (Any) –

  • converter (BaseConverter) –

  • unstructure_to (Any) –

Return type

Callable[[Tuple[Any, …]], Any]

cattr.gen.make_iterable_unstructure_fn(cl, converter, unstructure_to=None)[source]

Generate a specialized unstructure function for an iterable.

Parameters

  • cl (Any) –

  • converter (BaseConverter) –

  • unstructure_to (Any) –

Return type

Callable[[Iterable[Any]], Any]

cattr.gen.make_mapping_structure_fn(cl, converter, structure_to=<class 'dict'>, key_type=NOTHING, val_type=NOTHING, detailed_validation=True)[source]

Generate a specialized unstructure function for a mapping.

Parameters

  • cl (Type[cattrs.gen.T]) –

  • converter (BaseConverter) –

  • structure_to (Type) –

  • detailed_validation (bool) –

Return type

Callable[[Mapping[Any, Any], Any], cattrs.gen.T]

cattr.gen.make_mapping_unstructure_fn(cl, converter, unstructure_to=None, key_handler=None)[source]

Generate a specialized unstructure function for a mapping.

Parameters

  • cl (Any) –

  • converter (BaseConverter) –

  • unstructure_to (Any) –

  • key_handler (Optional[Callable[[Any, Optional[Any]], Any]]) –

Return type

Callable[[Mapping[Any, Any]], Any]

cattr.gen.override(omit_if_default=None, rename=None, omit=False)[source]
Parameters

  • omit_if_default (Optional[bool]) –

  • rename (Optional[str]) –

  • omit (bool) –

Module contents

class cattr.BaseConverter(dict_factory=<class 'dict'>, unstruct_strat=UnstructureStrategy.AS_DICT, prefer_attrib_converters=False, detailed_validation=True)[source]

Bases: object

Converts between structured and unstructured data.

Parameters
Return type

None

copy(dict_factory=None, unstruct_strat=None, prefer_attrib_converters=None, detailed_validation=None)[source]
Parameters

  • dict_factory (Optional[Callable[[], Any]]) –

  • unstruct_strat (Optional[cattrs.converters.UnstructureStrategy]) –

  • prefer_attrib_converters (Optional[bool]) –

  • detailed_validation (Optional[bool]) –

Return type

cattrs.converters.BaseConverter

detailed_validation
register_structure_hook(cl, func)[source]

Register a primitive-to-class converter function for a type.

The converter function should take two arguments:

  • a Python object to be converted,

  • the type to convert to

and return the instance of the class. The type may seem redundant, but is sometimes needed (for example, when dealing with generic classes).

Parameters

  • cl (Any) –

  • func (Callable[[Any, Type[cattrs.converters.T]], cattrs.converters.T]) –

Return type

None

register_structure_hook_factory(predicate, factory)[source]

Register a hook factory for a given predicate.

A predicate is a function that, given a type, returns whether the factory can produce a hook for that type.

A factory is a callable that, given a type, produces a structuring hook for that type. This structuring hook will be cached.

Parameters

  • predicate (Callable[[Any], bool]) –

  • factory (Callable[[Any], Callable[[Any, Any], Any]]) –

Return type

None

register_structure_hook_func(check_func, func)[source]

Register a class-to-primitive converter function for a class, using a function to check if it’s a match.

Parameters

  • check_func (Callable[[Type[cattrs.converters.T]], bool]) –

  • func (Callable[[Any, Type[cattrs.converters.T]], cattrs.converters.T]) –

Return type

None

register_unstructure_hook(cls, func)[source]

Register a class-to-primitive converter function for a class.

The converter function should take an instance of the class and return its Python equivalent.

Parameters

  • cls (Any) –

  • func (Callable[[Any], Any]) –

Return type

None

register_unstructure_hook_factory(predicate, factory)[source]

Register a hook factory for a given predicate.

A predicate is a function that, given a type, returns whether the factory can produce a hook for that type.

A factory is a callable that, given a type, produces an unstructuring hook for that type. This unstructuring hook will be cached.

Parameters

  • predicate (Callable[[Any], bool]) –

  • factory (Callable[[Any], Callable[[Any], Any]]) –

Return type

None

register_unstructure_hook_func(check_func, func)[source]

Register a class-to-primitive converter function for a class, using a function to check if it’s a match.

Parameters

  • check_func (Callable[[Any], bool]) –

  • func (Callable[[Any], Any]) –

Return type

None

structure(obj, cl)[source]

Convert unstructured Python data structures to structured data.

Parameters

  • obj (Any) –

  • cl (Type[cattrs.converters.T]) –

Return type

cattrs.converters.T

structure_attrs_fromdict(obj, cl)[source]

Instantiate an attrs class from a mapping (dict).

Parameters

  • obj (collections.abc.Mapping[str, Any]) –

  • cl (Type[cattrs.converters.T]) –

Return type

cattrs.converters.T

structure_attrs_fromtuple(obj, cl)[source]

Load an attrs class from a sequence (tuple).

Parameters

  • obj (Tuple[Any, ...]) –

  • cl (Type[cattrs.converters.T]) –

Return type

cattrs.converters.T

property unstruct_strat: cattrs.converters.UnstructureStrategy

The default way of unstructuring attrs classes.

unstructure(obj, unstructure_as=None)[source]
Parameters

  • obj (Any) –

  • unstructure_as (Optional[Any]) –

Return type

Any

unstructure_attrs_asdict(obj)[source]

Our version of attrs.asdict, so we can call back to us.

Parameters

obj (Any) –

Return type

Dict[str, Any]

unstructure_attrs_astuple(obj)[source]

Our version of attrs.astuple, so we can call back to us.

Parameters

obj (Any) –

Return type

Tuple[Any, …]

class cattr.Converter(dict_factory=<class 'dict'>, unstruct_strat=UnstructureStrategy.AS_DICT, omit_if_default=False, forbid_extra_keys=False, type_overrides={}, unstruct_collection_overrides={}, prefer_attrib_converters=False, detailed_validation=True)[source]

Bases: cattrs.converters.BaseConverter

A converter which generates specialized un/structuring functions.

Parameters

  • dict_factory (Callable[[], Any]) –

  • unstruct_strat (cattrs.converters.UnstructureStrategy) –

  • omit_if_default (bool) –

  • forbid_extra_keys (bool) –

  • type_overrides (collections.abc.Mapping[Type, cattrs.gen.AttributeOverride]) –

  • unstruct_collection_overrides (collections.abc.Mapping[Type, Callable]) –

  • prefer_attrib_converters (bool) –

  • detailed_validation (bool) –

copy(dict_factory=None, unstruct_strat=None, omit_if_default=None, forbid_extra_keys=None, type_overrides=None, unstruct_collection_overrides=None, prefer_attrib_converters=None, detailed_validation=None)[source]
Parameters

  • dict_factory (Optional[Callable[[], Any]]) –

  • unstruct_strat (Optional[cattrs.converters.UnstructureStrategy]) –

  • omit_if_default (Optional[bool]) –

  • forbid_extra_keys (Optional[bool]) –

  • type_overrides (Optional[collections.abc.Mapping[Type, cattrs.gen.AttributeOverride]]) –

  • unstruct_collection_overrides (Optional[collections.abc.Mapping[Type, Callable]]) –

  • prefer_attrib_converters (Optional[bool]) –

  • detailed_validation (Optional[bool]) –

Return type

cattrs.converters.Converter

forbid_extra_keys
gen_structure_annotated(type)[source]
gen_structure_attrs_fromdict(cl)[source]
Parameters

cl (Type[cattrs.converters.T]) –

Return type

Callable[[collections.abc.Mapping[str, Any], Any], cattrs.converters.T]

gen_structure_counter(cl)[source]
Parameters

cl (Any) –

Return type

Callable[[Mapping[Any, Any], Any], cattrs.converters.T]

gen_structure_mapping(cl)[source]
Parameters

cl (Any) –

Return type

Callable[[Mapping[Any, Any], Any], cattrs.converters.T]

gen_unstructure_annotated(type)[source]
gen_unstructure_attrs_fromdict(cl)[source]
Parameters

cl (Type[cattrs.converters.T]) –

Return type

Callable[[cattrs.converters.T], Dict[str, Any]]

gen_unstructure_hetero_tuple(cl, unstructure_to=None)[source]
Parameters

  • cl (Any) –

  • unstructure_to (Optional[Any]) –

Return type

Callable[[Tuple[Any, …]], Any]

gen_unstructure_iterable(cl, unstructure_to=None)[source]
Parameters

  • cl (Any) –

  • unstructure_to (Optional[Any]) –

Return type

Callable[[Iterable[Any]], Any]

gen_unstructure_mapping(cl, unstructure_to=None, key_handler=None)[source]
Parameters

  • cl (Any) –

  • unstructure_to (Optional[Any]) –

  • key_handler (Optional[Callable[[Any, Optional[Any]], Any]]) –

Return type

Callable[[Mapping[Any, Any]], Any]

get_structure_newtype(type)[source]
Parameters

type (Type[cattrs.converters.T]) –

Return type

Callable[[Any, Any], cattrs.converters.T]

omit_if_default
type_overrides
cattr.GenConverter

alias of cattrs.converters.Converter

class cattr.UnstructureStrategy(value)[source]

Bases: enum.Enum

attrs classes unstructuring strategies.

AS_DICT = 'asdict'
AS_TUPLE = 'astuple'
cattr.override(omit_if_default=None, rename=None, omit=False)[source]
Parameters

  • omit_if_default (Optional[bool]) –

  • rename (Optional[str]) –

  • omit (bool) –

cattr.structure(obj, cl)

Convert unstructured Python data structures to structured data.

Parameters

  • obj (Any) –

  • cl (Type[cattrs.converters.T]) –

Return type

cattrs.converters.T

cattr.structure_attrs_fromdict(obj, cl)

Instantiate an attrs class from a mapping (dict).

Parameters

  • obj (collections.abc.Mapping[str, Any]) –

  • cl (Type[cattrs.converters.T]) –

Return type

cattrs.converters.T

cattr.structure_attrs_fromtuple(obj, cl)

Load an attrs class from a sequence (tuple).

Parameters

  • obj (Tuple[Any, ...]) –

  • cl (Type[cattrs.converters.T]) –

Return type

cattrs.converters.T

cattr.unstructure(obj, unstructure_as=None)
Parameters

  • obj (Any) –

  • unstructure_as (Optional[Any]) –

Return type

Any