Skip to content

prefect.server.utilities.schemas

Utilities for creating and working with Prefect REST API schemas.

SubclassMethodMixin

Source code in /home/runner/work/docs/docs/prefect_source/src/prefect/server/utilities/schemas.py 
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
class SubclassMethodMixin:
    @classmethod
    def subclass(
        cls: Type[B],
        name: str = None,
        include_fields: List[str] = None,
        exclude_fields: List[str] = None,
    ) -> Type[B]:
        """Creates a subclass of this model containing only the specified fields.

        See `pydantic_subclass()`.

        Args:
            name (str, optional): a name for the subclass
            include_fields (List[str], optional): fields to include
            exclude_fields (List[str], optional): fields to exclude

        Returns:
            BaseModel: a subclass of this class
        """
        return pydantic_subclass(
            base=cls,
            name=name,
            include_fields=include_fields,
            exclude_fields=exclude_fields,
        )

subclass classmethod

Creates a subclass of this model containing only the specified fields.

See pydantic_subclass().

Parameters:

Name Type Description Default
name str

a name for the subclass

 None
include_fields List[str]

fields to include

 None
exclude_fields List[str]

fields to exclude

 None

Returns:

Name Type Description
BaseModel Type[B]

a subclass of this class
Source code in /home/runner/work/docs/docs/prefect_source/src/prefect/server/utilities/schemas.py 
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
@classmethod
def subclass(
    cls: Type[B],
    name: str = None,
    include_fields: List[str] = None,
    exclude_fields: List[str] = None,
) -> Type[B]:
    """Creates a subclass of this model containing only the specified fields.

    See `pydantic_subclass()`.

    Args:
        name (str, optional): a name for the subclass
        include_fields (List[str], optional): fields to include
        exclude_fields (List[str], optional): fields to exclude

    Returns:
        BaseModel: a subclass of this class
    """
    return pydantic_subclass(
        base=cls,
        name=name,
        include_fields=include_fields,
        exclude_fields=exclude_fields,
    )

pydantic_subclass

Creates a subclass of a Pydantic model that excludes certain fields. Pydantic models use the fields attribute of their parent class to determine inherited fields, so to create a subclass without fields, we temporarily remove those fields from the parent fields and use create_model to dynamically generate a new subclass.

Parameters:

Name Type Description Default
base BaseModel

a Pydantic BaseModel

 required
name str

a name for the subclass. If not provided it will have the same name as the base class.

 None
include_fields List[str]

a set of field names to include. If None, all fields are included.

 None
exclude_fields List[str]

a list of field names to exclude. If None, no fields are excluded.

 None

Returns:

Type Description
Type[B]

pydantic.BaseModel: a new model subclass that contains only the specified fields.
Example

To subclass a model with a subset of fields: 

class Parent(pydantic.BaseModel):
    x: int = 1
    y: int = 2

Child = pydantic_subclass(Parent, 'Child', exclude_fields=['y'])
assert hasattr(Child(), 'x')
assert not hasattr(Child(), 'y')

To subclass a model with a subset of fields but include a new field: 

class Child(pydantic_subclass(Parent, exclude_fields=['y'])):
    z: int = 3

assert hasattr(Child(), 'x')
assert not hasattr(Child(), 'y')
assert hasattr(Child(), 'z')

Source code in /home/runner/work/docs/docs/prefect_source/src/prefect/server/utilities/schemas.py 
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
def pydantic_subclass(
    base: Type[B],
    name: str = None,
    include_fields: List[str] = None,
    exclude_fields: List[str] = None,
) -> Type[B]:
    """Creates a subclass of a Pydantic model that excludes certain fields.
    Pydantic models use the __fields__ attribute of their parent class to
    determine inherited fields, so to create a subclass without fields, we
    temporarily remove those fields from the parent __fields__ and use
    `create_model` to dynamically generate a new subclass.

    Args:
        base (pydantic.BaseModel): a Pydantic BaseModel
        name (str): a name for the subclass. If not provided
            it will have the same name as the base class.
        include_fields (List[str]): a set of field names to include.
            If `None`, all fields are included.
        exclude_fields (List[str]): a list of field names to exclude.
            If `None`, no fields are excluded.

    Returns:
        pydantic.BaseModel: a new model subclass that contains only the specified fields.

    Example:
        To subclass a model with a subset of fields:
        ```python
        class Parent(pydantic.BaseModel):
            x: int = 1
            y: int = 2

        Child = pydantic_subclass(Parent, 'Child', exclude_fields=['y'])
        assert hasattr(Child(), 'x')
        assert not hasattr(Child(), 'y')
        ```

        To subclass a model with a subset of fields but include a new field:
        ```python
        class Child(pydantic_subclass(Parent, exclude_fields=['y'])):
            z: int = 3

        assert hasattr(Child(), 'x')
        assert not hasattr(Child(), 'y')
        assert hasattr(Child(), 'z')
        ```
    """

    # collect field names
    field_names = set(include_fields or base.__fields__)
    excluded_fields = set(exclude_fields or [])
    if field_names.difference(base.__fields__):
        raise ValueError(
            "Included fields not found on base class: "
            f"{field_names.difference(base.__fields__)}"
        )
    elif excluded_fields.difference(base.__fields__):
        raise ValueError(
            "Excluded fields not found on base class: "
            f"{excluded_fields.difference(base.__fields__)}"
        )
    field_names.difference_update(excluded_fields)

    # create a new class that inherits from `base` but only contains the specified
    # pydantic __fields__
    new_cls = type(
        name or base.__name__,
        (base,),
        {
            "__fields__": {
                k: copy.copy(v) for k, v in base.__fields__.items() if k in field_names
            }
        },
    )

    return new_cls