TypeAdapter
Bases: Generic[T]
Usage Documentation
Type adapters provide a flexible way to perform validation and serialization based on a Python type.
A TypeAdapter
instance exposes some of the functionality from BaseModel
instance methods
for types that do not have such methods (such as dataclasses, primitive types, and more).
Note: TypeAdapter
instances are not types, and cannot be used as type annotations for fields.
Attributes:
Name | Type | Description |
---|---|---|
core_schema |
CoreSchema
|
The core schema for the type. |
validator |
SchemaValidator
|
The schema validator for the type. |
serializer |
SchemaSerializer
|
The schema serializer for the type. |
Namespace management nuances and implementation details
Here, we collect some notes on namespace management, and subtle differences from BaseModel
:
BaseModel
uses its own __module__
to find out where it was defined
and then looks for symbols to resolve forward references in those globals.
On the other hand, TypeAdapter
can be initialized with arbitrary objects,
which may not be types and thus do not have a __module__
available.
So instead we look at the globals in our parent stack frame.
It is expected that the ns_resolver
passed to this function will have the correct
namespace for the type we're adapting. See TypeAdapter.__init__
and TypeAdapter.rebuild
for various ways to construct this namespace.
This works for the case where this function is called in a module that has the target of forward references in its scope, but does not always work for more complex cases.
For example, take the following:
a.py
from typing import Dict, List
IntList = List[int]
OuterDict = Dict[str, 'IntList']
b.py
from a import OuterDict
from pydantic import TypeAdapter
IntList = int # replaces the symbol the forward reference is looking for
v = TypeAdapter(OuterDict)
v({'x': 1}) # should fail but doesn't
If OuterDict
were a BaseModel
, this would work because it would resolve
the forward reference within the a.py
namespace.
But TypeAdapter(OuterDict)
can't determine what module OuterDict
came from.
In other words, the assumption that all forward references exist in the
module we are being called from is not technically always true.
Although most of the time it is and it works fine for recursive models and such,
BaseModel
's behavior isn't perfect either and can break in similar ways,
so there is no right or wrong between the two.
But at the very least this behavior is subtly different from BaseModel
's.
Parameters:
Name | Type | Description | Default |
---|---|---|---|
type |
Any
|
The type associated with the |
required |
config |
ConfigDict | None
|
Configuration for the |
None
|
_parent_depth |
int
|
Depth at which to search the for the parent namespace used for schema building.
We also use this as a reference level to find the global namespace (_parent_depth - 1).
Defaults to 2 because we expect to reference the frame that called the |
2
|
module |
str | None
|
The module that passes to plugin if provided. |
None
|
Note
You cannot use the config
argument when instantiating a TypeAdapter
if the type you're using has its own
config that cannot be overridden (ex: BaseModel
, TypedDict
, and dataclass
). A
type-adapter-config-unused
error will be raised in this case.
Note
The _parent_depth
argument is named with an underscore to suggest its private nature and discourage use.
It may be deprecated in a minor version, so we only recommend using it if you're
comfortable with potential change in behavior / support.
Compatibility with mypy
Depending on the type used, mypy
might raise an error when instantiating a TypeAdapter
. As a workaround, you can explicitly
annotate your variable:
from typing import Union
from pydantic import TypeAdapter
ta: TypeAdapter[Union[str, int]] = TypeAdapter(Union[str, int]) # type: ignore[arg-type]
Returns:
Type | Description |
---|---|
None
|
A type adapter configured for the specified |
Source code in pydantic/type_adapter.py
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|
rebuild ¶
rebuild(
*,
force: bool = False,
raise_errors: bool = True,
_parent_namespace_depth: int = 2,
_types_namespace: MappingNamespace | None = None
) -> bool | None
Try to rebuild the pydantic-core schema for the adapter's type.
This may be necessary when one of the annotations is a ForwardRef which could not be resolved during the initial attempt to build the schema, and automatic rebuilding fails.
Parameters:
Name | Type | Description | Default |
---|---|---|---|
force |
bool
|
Whether to force the rebuilding of the type adapter's schema, defaults to |
False
|
raise_errors |
bool
|
Whether to raise errors, defaults to |
True
|
_parent_namespace_depth |
int
|
The depth level of the parent namespace, defaults to 2. |
2
|
_types_namespace |
MappingNamespace | None
|
The types namespace, defaults to |
None
|
Returns:
Type | Description |
---|---|
bool | None
|
Returns |
bool | None
|
If rebuilding was required, returns |
Source code in pydantic/type_adapter.py
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validate_python ¶
validate_python(
object: Any,
/,
*,
strict: bool | None = None,
from_attributes: bool | None = None,
context: dict[str, Any] | None = None,
experimental_allow_partial: (
bool | Literal["off", "on", "trailing-strings"]
) = False,
) -> T
Validate a Python object against the model.
Parameters:
Name | Type | Description | Default |
---|---|---|---|
object |
Any
|
The Python object to validate against the model. |
required |
strict |
bool | None
|
Whether to strictly check types. |
None
|
from_attributes |
bool | None
|
Whether to extract data from object attributes. |
None
|
context |
dict[str, Any] | None
|
Additional context to pass to the validator. |
None
|
experimental_allow_partial |
bool | Literal['off', 'on', 'trailing-strings']
|
Experimental whether to enable partial validation, e.g. to process streams. * False / 'off': Default behavior, no partial validation. * True / 'on': Enable partial validation. * 'trailing-strings': Enable partial validation and allow trailing strings in the input. |
False
|
Note
When using TypeAdapter
with a Pydantic dataclass
, the use of the from_attributes
argument is not supported.
Returns:
Type | Description |
---|---|
T
|
The validated object. |
Source code in pydantic/type_adapter.py
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|
validate_json ¶
validate_json(
data: str | bytes | bytearray,
/,
*,
strict: bool | None = None,
context: dict[str, Any] | None = None,
experimental_allow_partial: (
bool | Literal["off", "on", "trailing-strings"]
) = False,
) -> T
Usage Documentation
Validate a JSON string or bytes against the model.
Parameters:
Name | Type | Description | Default |
---|---|---|---|
data |
str | bytes | bytearray
|
The JSON data to validate against the model. |
required |
strict |
bool | None
|
Whether to strictly check types. |
None
|
context |
dict[str, Any] | None
|
Additional context to use during validation. |
None
|
experimental_allow_partial |
bool | Literal['off', 'on', 'trailing-strings']
|
Experimental whether to enable partial validation, e.g. to process streams. * False / 'off': Default behavior, no partial validation. * True / 'on': Enable partial validation. * 'trailing-strings': Enable partial validation and allow trailing strings in the input. |
False
|
Returns:
Type | Description |
---|---|
T
|
The validated object. |
Source code in pydantic/type_adapter.py
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|
validate_strings ¶
validate_strings(
obj: Any,
/,
*,
strict: bool | None = None,
context: dict[str, Any] | None = None,
experimental_allow_partial: (
bool | Literal["off", "on", "trailing-strings"]
) = False,
) -> T
Validate object contains string data against the model.
Parameters:
Name | Type | Description | Default |
---|---|---|---|
obj |
Any
|
The object contains string data to validate. |
required |
strict |
bool | None
|
Whether to strictly check types. |
None
|
context |
dict[str, Any] | None
|
Additional context to use during validation. |
None
|
experimental_allow_partial |
bool | Literal['off', 'on', 'trailing-strings']
|
Experimental whether to enable partial validation, e.g. to process streams. * False / 'off': Default behavior, no partial validation. * True / 'on': Enable partial validation. * 'trailing-strings': Enable partial validation and allow trailing strings in the input. |
False
|
Returns:
Type | Description |
---|---|
T
|
The validated object. |
Source code in pydantic/type_adapter.py
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get_default_value ¶
get_default_value(
*,
strict: bool | None = None,
context: dict[str, Any] | None = None
) -> Some[T] | None
Get the default value for the wrapped type.
Parameters:
Name | Type | Description | Default |
---|---|---|---|
strict |
bool | None
|
Whether to strictly check types. |
None
|
context |
dict[str, Any] | None
|
Additional context to pass to the validator. |
None
|
Returns:
Type | Description |
---|---|
Some[T] | None
|
The default value wrapped in a |
Source code in pydantic/type_adapter.py
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|
dump_python ¶
dump_python(
instance: T,
/,
*,
mode: Literal["json", "python"] = "python",
include: IncEx | None = None,
exclude: IncEx | None = None,
by_alias: bool = False,
exclude_unset: bool = False,
exclude_defaults: bool = False,
exclude_none: bool = False,
round_trip: bool = False,
warnings: (
bool | Literal["none", "warn", "error"]
) = True,
serialize_as_any: bool = False,
context: dict[str, Any] | None = None,
) -> Any
Dump an instance of the adapted type to a Python object.
Parameters:
Name | Type | Description | Default |
---|---|---|---|
instance |
T
|
The Python object to serialize. |
required |
mode |
Literal['json', 'python']
|
The output format. |
'python'
|
include |
IncEx | None
|
Fields to include in the output. |
None
|
exclude |
IncEx | None
|
Fields to exclude from the output. |
None
|
by_alias |
bool
|
Whether to use alias names for field names. |
False
|
exclude_unset |
bool
|
Whether to exclude unset fields. |
False
|
exclude_defaults |
bool
|
Whether to exclude fields with default values. |
False
|
exclude_none |
bool
|
Whether to exclude fields with None values. |
False
|
round_trip |
bool
|
Whether to output the serialized data in a way that is compatible with deserialization. |
False
|
warnings |
bool | Literal['none', 'warn', 'error']
|
How to handle serialization errors. False/"none" ignores them, True/"warn" logs errors,
"error" raises a |
True
|
serialize_as_any |
bool
|
Whether to serialize fields with duck-typing serialization behavior. |
False
|
context |
dict[str, Any] | None
|
Additional context to pass to the serializer. |
None
|
Returns:
Type | Description |
---|---|
Any
|
The serialized object. |
Source code in pydantic/type_adapter.py
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dump_json ¶
dump_json(
instance: T,
/,
*,
indent: int | None = None,
include: IncEx | None = None,
exclude: IncEx | None = None,
by_alias: bool = False,
exclude_unset: bool = False,
exclude_defaults: bool = False,
exclude_none: bool = False,
round_trip: bool = False,
warnings: (
bool | Literal["none", "warn", "error"]
) = True,
serialize_as_any: bool = False,
context: dict[str, Any] | None = None,
) -> bytes
Usage Documentation
Serialize an instance of the adapted type to JSON.
Parameters:
Name | Type | Description | Default |
---|---|---|---|
instance |
T
|
The instance to be serialized. |
required |
indent |
int | None
|
Number of spaces for JSON indentation. |
None
|
include |
IncEx | None
|
Fields to include. |
None
|
exclude |
IncEx | None
|
Fields to exclude. |
None
|
by_alias |
bool
|
Whether to use alias names for field names. |
False
|
exclude_unset |
bool
|
Whether to exclude unset fields. |
False
|
exclude_defaults |
bool
|
Whether to exclude fields with default values. |
False
|
exclude_none |
bool
|
Whether to exclude fields with a value of |
False
|
round_trip |
bool
|
Whether to serialize and deserialize the instance to ensure round-tripping. |
False
|
warnings |
bool | Literal['none', 'warn', 'error']
|
How to handle serialization errors. False/"none" ignores them, True/"warn" logs errors,
"error" raises a |
True
|
serialize_as_any |
bool
|
Whether to serialize fields with duck-typing serialization behavior. |
False
|
context |
dict[str, Any] | None
|
Additional context to pass to the serializer. |
None
|
Returns:
Type | Description |
---|---|
bytes
|
The JSON representation of the given instance as bytes. |
Source code in pydantic/type_adapter.py
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json_schema ¶
json_schema(
*,
by_alias: bool = True,
ref_template: str = DEFAULT_REF_TEMPLATE,
schema_generator: type[
GenerateJsonSchema
] = GenerateJsonSchema,
mode: JsonSchemaMode = "validation"
) -> dict[str, Any]
Generate a JSON schema for the adapted type.
Parameters:
Name | Type | Description | Default |
---|---|---|---|
by_alias |
bool
|
Whether to use alias names for field names. |
True
|
ref_template |
str
|
The format string used for generating $ref strings. |
DEFAULT_REF_TEMPLATE
|
schema_generator |
type[GenerateJsonSchema]
|
The generator class used for creating the schema. |
GenerateJsonSchema
|
mode |
JsonSchemaMode
|
The mode to use for schema generation. |
'validation'
|
Returns:
Type | Description |
---|---|
dict[str, Any]
|
The JSON schema for the model as a dictionary. |
Source code in pydantic/type_adapter.py
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|
json_schemas
staticmethod
¶
json_schemas(
inputs: Iterable[
tuple[
JsonSchemaKeyT, JsonSchemaMode, TypeAdapter[Any]
]
],
/,
*,
by_alias: bool = True,
title: str | None = None,
description: str | None = None,
ref_template: str = DEFAULT_REF_TEMPLATE,
schema_generator: type[
GenerateJsonSchema
] = GenerateJsonSchema,
) -> tuple[
dict[
tuple[JsonSchemaKeyT, JsonSchemaMode],
JsonSchemaValue,
],
JsonSchemaValue,
]
Generate a JSON schema including definitions from multiple type adapters.
Parameters:
Name | Type | Description | Default |
---|---|---|---|
inputs |
Iterable[tuple[JsonSchemaKeyT, JsonSchemaMode, TypeAdapter[Any]]]
|
Inputs to schema generation. The first two items will form the keys of the (first) output mapping; the type adapters will provide the core schemas that get converted into definitions in the output JSON schema. |
required |
by_alias |
bool
|
Whether to use alias names. |
True
|
title |
str | None
|
The title for the schema. |
None
|
description |
str | None
|
The description for the schema. |
None
|
ref_template |
str
|
The format string used for generating $ref strings. |
DEFAULT_REF_TEMPLATE
|
schema_generator |
type[GenerateJsonSchema]
|
The generator class used for creating the schema. |
GenerateJsonSchema
|
Returns:
Type | Description |
---|---|
tuple[dict[tuple[JsonSchemaKeyT, JsonSchemaMode], JsonSchemaValue], JsonSchemaValue]
|
A tuple where:
|
Source code in pydantic/type_adapter.py
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