Fields
Defining fields on models.
Field ¶
Field(
default=PydanticUndefined,
*,
default_factory=_Unset,
alias=_Unset,
alias_priority=_Unset,
validation_alias=_Unset,
serialization_alias=_Unset,
title=_Unset,
description=_Unset,
examples=_Unset,
exclude=_Unset,
include=_Unset,
discriminator=_Unset,
json_schema_extra=_Unset,
frozen=_Unset,
validate_default=_Unset,
repr=_Unset,
init_var=_Unset,
kw_only=_Unset,
pattern=_Unset,
strict=_Unset,
gt=_Unset,
ge=_Unset,
lt=_Unset,
le=_Unset,
multiple_of=_Unset,
allow_inf_nan=_Unset,
max_digits=_Unset,
decimal_places=_Unset,
min_length=_Unset,
max_length=_Unset,
**extra
)
Usage Documentation
Create a field for objects that can be configured.
Used to provide extra information about a field, either for the model schema or complex validation. Some arguments
apply only to number fields (int
, float
, Decimal
) and some apply only to str
.
Parameters:
Name | Type | Description | Default |
---|---|---|---|
default |
Any
|
Default value if the field is not set. |
PydanticUndefined
|
default_factory |
typing.Callable[[], Any] | None
|
A callable to generate the default value, such as :func: |
_Unset
|
alias |
str | None
|
An alternative name for the attribute. |
_Unset
|
alias_priority |
int | None
|
Priority of the alias. This affects whether an alias generator is used. |
_Unset
|
validation_alias |
str | AliasPath | AliasChoices | None
|
'Whitelist' validation step. The field will be the single one allowed by the alias or set of aliases defined. |
_Unset
|
serialization_alias |
str | None
|
'Blacklist' validation step. The vanilla field will be the single one of the alias' or set of aliases' fields and all the other fields will be ignored at serialization time. |
_Unset
|
title |
str | None
|
Human-readable title. |
_Unset
|
description |
str | None
|
Human-readable description. |
_Unset
|
examples |
list[Any] | None
|
Example values for this field. |
_Unset
|
exclude |
bool | None
|
Whether to exclude the field from the model schema. |
_Unset
|
include |
bool | None
|
Whether to include the field in the model schema. |
_Unset
|
discriminator |
str | None
|
Field name for discriminating the type in a tagged union. |
_Unset
|
json_schema_extra |
dict[str, Any] | typing.Callable[[dict[str, Any]], None] | None
|
Any additional JSON schema data for the schema property. |
_Unset
|
frozen |
bool | None
|
Whether the field is frozen. |
_Unset
|
validate_default |
bool | None
|
Run validation that isn't only checking existence of defaults. |
_Unset
|
repr |
bool
|
A boolean indicating whether to include the field in the |
_Unset
|
init_var |
bool | None
|
Whether the field should be included in the constructor of the dataclass. |
_Unset
|
kw_only |
bool | None
|
Whether the field should be a keyword-only argument in the constructor of the dataclass. |
_Unset
|
strict |
bool | None
|
If |
_Unset
|
gt |
float | None
|
Greater than. If set, value must be greater than this. Only applicable to numbers. |
_Unset
|
ge |
float | None
|
Greater than or equal. If set, value must be greater than or equal to this. Only applicable to numbers. |
_Unset
|
lt |
float | None
|
Less than. If set, value must be less than this. Only applicable to numbers. |
_Unset
|
le |
float | None
|
Less than or equal. If set, value must be less than or equal to this. Only applicable to numbers. |
_Unset
|
multiple_of |
float | None
|
Value must be a multiple of this. Only applicable to numbers. |
_Unset
|
min_length |
int | None
|
Minimum length for strings. |
_Unset
|
max_length |
int | None
|
Maximum length for strings. |
_Unset
|
pattern |
str | None
|
Pattern for strings. |
_Unset
|
allow_inf_nan |
bool | None
|
Allow |
_Unset
|
max_digits |
int | None
|
Maximum number of allow digits for strings. |
_Unset
|
decimal_places |
int | None
|
Maximum number of decimal places allowed for numbers. |
_Unset
|
extra |
Unpack[_EmptyKwargs]
|
Include extra fields used by the JSON schema. Warning The |
{}
|
Returns:
Type | Description |
---|---|
Any
|
A new |
Source code in pydantic/fields.py
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|
FieldInfo ¶
FieldInfo(**kwargs)
Bases: _repr.Representation
This class holds information about a field.
FieldInfo
is used for any field definition regardless of whether the Field()
function is explicitly used.
Warning
You generally shouldn't be creating FieldInfo
directly, you'll only need to use it when accessing
BaseModel
.model_fields
internals.
Attributes:
Name | Type | Description |
---|---|---|
annotation |
type[Any] | None
|
The type annotation of the field. |
default |
Any
|
The default value of the field. |
default_factory |
typing.Callable[[], Any] | None
|
The factory function used to construct the default for the field. |
alias |
str | None
|
The alias name of the field. |
alias_priority |
int | None
|
The priority of the field's alias. |
validation_alias |
str | AliasPath | AliasChoices | None
|
The validation alias name of the field. |
serialization_alias |
str | None
|
The serialization alias name of the field. |
title |
str | None
|
The title of the field. |
description |
str | None
|
The description of the field. |
examples |
list[Any] | None
|
List of examples of the field. |
exclude |
bool | None
|
Whether to exclude the field from the model schema. |
include |
bool | None
|
Whether to include the field in the model schema. |
discriminator |
str | None
|
Field name for discriminating the type in a tagged union. |
json_schema_extra |
dict[str, Any] | typing.Callable[[dict[str, Any]], None] | None
|
Dictionary of extra JSON schema properties. |
frozen |
bool | None
|
Whether the field is frozen. |
validate_default |
bool | None
|
Whether to validate the default value of the field. |
repr |
bool
|
Whether to include the field in representation of the model. |
init_var |
bool | None
|
Whether the field should be included in the constructor of the dataclass. |
kw_only |
bool | None
|
Whether the field should be a keyword-only argument in the constructor of the dataclass. |
metadata |
list[Any]
|
List of metadata constraints. |
See the signature of pydantic.fields.Field
for more details about the expected arguments.
Source code in pydantic/fields.py
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|
from_field
classmethod
¶
from_field(default=PydanticUndefined, **kwargs)
Create a new FieldInfo
object with the Field
function.
Parameters:
Name | Type | Description | Default |
---|---|---|---|
default |
Any
|
The default value for the field. Defaults to Undefined. |
PydanticUndefined
|
**kwargs |
Unpack[_FromFieldInfoInputs]
|
Additional arguments dictionary. |
{}
|
Raises:
Type | Description |
---|---|
TypeError
|
If 'annotation' is passed as a keyword argument. |
Returns:
Type | Description |
---|---|
typing_extensions.Self
|
A new FieldInfo object with the given parameters. |
Example
This is how you can create a field with default value like this:
import pydantic
class MyModel(pydantic.BaseModel):
foo: int = pydantic.Field(4)
Source code in pydantic/fields.py
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|
from_annotation
classmethod
¶
from_annotation(annotation)
Creates a FieldInfo
instance from a bare annotation.
Parameters:
Name | Type | Description | Default |
---|---|---|---|
annotation |
type[Any]
|
An annotation object. |
required |
Returns:
Type | Description |
---|---|
typing_extensions.Self
|
An instance of the field metadata. |
Example
This is how you can create a field from a bare annotation like this:
import pydantic
class MyModel(pydantic.BaseModel):
foo: int # <-- like this
We also account for the case where the annotation can be an instance of Annotated
and where
one of the (not first) arguments in Annotated
are an instance of FieldInfo
, e.g.:
import annotated_types
from typing_extensions import Annotated
import pydantic
class MyModel(pydantic.BaseModel):
foo: Annotated[int, annotated_types.Gt(42)]
bar: Annotated[int, pydantic.Field(gt=42)]
Source code in pydantic/fields.py
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|
from_annotated_attribute
classmethod
¶
from_annotated_attribute(annotation, default)
Create FieldInfo
from an annotation with a default value.
Parameters:
Name | Type | Description | Default |
---|---|---|---|
annotation |
type[Any]
|
The type annotation of the field. |
required |
default |
Any
|
The default value of the field. |
required |
Returns:
Type | Description |
---|---|
typing_extensions.Self
|
A field object with the passed values. |
Example
import annotated_types
from typing_extensions import Annotated
import pydantic
class MyModel(pydantic.BaseModel):
foo: int = 4 # <-- like this
bar: Annotated[int, annotated_types.Gt(4)] = 4 # <-- or this
spam: Annotated[int, pydantic.Field(gt=4)] = 4 # <-- or this
Source code in pydantic/fields.py
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|
merge_field_infos
staticmethod
¶
merge_field_infos(*field_infos, **overrides)
Merge FieldInfo
instances keeping only explicitly set attributes.
Later FieldInfo
instances override earlier ones.
Returns:
Name | Type | Description |
---|---|---|
FieldInfo |
FieldInfo
|
A merged FieldInfo instance. |
Source code in pydantic/fields.py
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|
get_default ¶
get_default(*, call_default_factory=False)
Get the default value.
We expose an option for whether to call the default_factory (if present), as calling it may
result in side effects that we want to avoid. However, there are times when it really should
be called (namely, when instantiating a model via model_construct
).
Parameters:
Name | Type | Description | Default |
---|---|---|---|
call_default_factory |
bool
|
Whether to call the default_factory or not. Defaults to |
False
|
Returns:
Type | Description |
---|---|
Any
|
The default value, calling the default factory if requested or |
Source code in pydantic/fields.py
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|
is_required ¶
is_required()
Check if the argument is required.
Returns:
Type | Description |
---|---|
bool
|
|
Source code in pydantic/fields.py
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|
rebuild_annotation ¶
rebuild_annotation()
Rebuilds the original annotation for use in function signatures.
If metadata is present, it adds it to the original annotation using an
AnnotatedAlias
. Otherwise, it returns the original annotation as is.
Returns:
Type | Description |
---|---|
Any
|
The rebuilt annotation. |
Source code in pydantic/fields.py
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|
apply_typevars_map ¶
apply_typevars_map(typevars_map, types_namespace)
Apply a typevars_map
to the annotation.
This method is used when analyzing parametrized generic types to replace typevars with their concrete types.
This method applies the typevars_map
to the annotation in place.
Parameters:
Name | Type | Description | Default |
---|---|---|---|
typevars_map |
dict[Any, Any] | None
|
A dictionary mapping type variables to their concrete types. |
required |
types_namespace |
dict | None
|
A dictionary containing related types to the annotated type. |
required |
See Also
pydantic._internal._generics.replace_types is used for replacing the typevars with their concrete types.
Source code in pydantic/fields.py
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|
AliasChoices
dataclass
¶
AliasChoices(first_choice, *choices)
Usage Documentation
A data class used by validation_alias
as a convenience to create aliases.
Attributes:
Name | Type | Description |
---|---|---|
choices |
list[str | AliasPath]
|
A list containing a string or |
Source code in pydantic/fields.py
606 607 |
|
convert_to_aliases ¶
convert_to_aliases()
Converts arguments to a list of lists containing string or integer aliases.
Returns:
Type | Description |
---|---|
list[list[str | int]]
|
The list of aliases. |
Source code in pydantic/fields.py
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|
AliasPath
dataclass
¶
AliasPath(first_arg, *args)
Usage Documentation
A data class used by validation_alias
as a convenience to create aliases.
Attributes:
Name | Type | Description |
---|---|---|
path |
list[int | str]
|
A list of string or integer aliases. |
Source code in pydantic/fields.py
582 583 |
|
convert_to_aliases ¶
convert_to_aliases()
Converts arguments to a list of string or integer aliases.
Returns:
Type | Description |
---|---|
list[str | int]
|
The list of aliases. |
Source code in pydantic/fields.py
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|
PrivateAttr ¶
PrivateAttr(
default=PydanticUndefined, *, default_factory=None
)
Indicates that attribute is only used internally and never mixed with regular fields.
Private attributes are not checked by Pydantic, so it's up to you to maintain their accuracy.
Private attributes are stored in __private_attributes__
on the model.
Parameters:
Name | Type | Description | Default |
---|---|---|---|
default |
Any
|
The attribute's default value. Defaults to Undefined. |
PydanticUndefined
|
default_factory |
typing.Callable[[], Any] | None
|
Callable that will be
called when a default value is needed for this attribute.
If both |
None
|
Returns:
Type | Description |
---|---|
Any
|
An instance of |
Raises:
Type | Description |
---|---|
ValueError
|
If both |
Source code in pydantic/fields.py
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|
ModelPrivateAttr ¶
ModelPrivateAttr(
default=PydanticUndefined, *, default_factory=None
)
Bases: _repr.Representation
A descriptor for private attributes in class models.
Attributes:
Name | Type | Description |
---|---|---|
default |
The default value of the attribute if not provided. |
|
default_factory |
A callable function that generates the default value of the attribute if not provided. |
Source code in pydantic/fields.py
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|
get_default ¶
get_default()
Retrieve the default value of the object.
If self.default_factory
is None
, the method will return a deep copy of the self.default
object.
If self.default_factory
is not None
, it will call self.default_factory
and return the value returned.
Returns:
Type | Description |
---|---|
Any
|
The default value of the object. |
Source code in pydantic/fields.py
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|
computed_field ¶
computed_field(
__f=None,
*,
alias=None,
alias_priority=None,
title=None,
description=None,
repr=True,
return_type=PydanticUndefined
)
Usage Documentation
Decorator to include property
and cached_property
when serializing models.
If applied to functions not yet decorated with @property
or @cached_property
, the function is
automatically wrapped with property
.
Parameters:
Name | Type | Description | Default |
---|---|---|---|
__f |
PropertyT | None
|
the function to wrap. |
None
|
alias |
str | None
|
alias to use when serializing this computed field, only used when |
None
|
alias_priority |
int | None
|
priority of the alias. This affects whether an alias generator is used |
None
|
title |
str | None
|
Title to used when including this computed field in JSON Schema, currently unused waiting for #4697 |
None
|
description |
str | None
|
Description to used when including this computed field in JSON Schema, defaults to the functions docstring, currently unused waiting for #4697 |
None
|
repr |
bool
|
whether to include this computed field in model repr |
True
|
return_type |
Any
|
optional return for serialization logic to expect when serializing to JSON, if included
this must be correct, otherwise a |
PydanticUndefined
|
Returns:
Type | Description |
---|---|
PropertyT | typing.Callable[[PropertyT], PropertyT]
|
A proxy wrapper for the property. |
Source code in pydantic/fields.py
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|
ComputedFieldInfo
dataclass
¶
A container for data from @computed_field
so that we can access it while building the pydantic-core schema.
Attributes:
Name | Type | Description |
---|---|---|
decorator_repr |
str
|
A class variable representing the decorator string, '@computed_field'. |
wrapped_property |
property
|
The wrapped computed field property. |
return_type |
Any
|
The type of the computed field property's return value. |
alias |
str | None
|
The alias of the property to be used during encoding and decoding. |
alias_priority |
int | None
|
priority of the alias. This affects whether an alias generator is used |
title |
str | None
|
Title of the computed field as in OpenAPI document, should be a short summary. |
description |
str | None
|
Description of the computed field as in OpenAPI document. |
repr |
bool
|
A boolean indicating whether or not to include the field in the repr output. |