prefect.utilities.pydantic
¶
PartialModel
¶
Bases: Generic[M]
A utility for creating a Pydantic model in several steps.
Fields may be set at initialization, via attribute assignment, or at finalization when the concrete model is returned.
Pydantic validation does not occur until finalization.
Each field can only be set once and a ValueError
will be raised on assignment if
a field already has a value.
Example
class MyModel(pydantic_v1.BaseModel): x: int y: str z: float
partial_model = PartialModel(MyModel, x=1) partial_model.y = "two" model = partial_model.finalize(z=3.0)
Source code in prefect/utilities/pydantic.py
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add_cloudpickle_reduction
¶
Adds a __reducer__
to the given class that ensures it is cloudpickle compatible.
Workaround for issues with cloudpickle when using cythonized pydantic which throws exceptions when attempting to pickle the class which has "compiled" validator methods dynamically attached to it.
We cannot define this utility in the model class itself because the class is the type that contains unserializable methods.
Any model using some features of Pydantic (e.g. Path
validation) with a Cython
compiled Pydantic installation may encounter pickling issues.
See related issue at https://github.com/cloudpipe/cloudpickle/issues/408
Source code in prefect/utilities/pydantic.py
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add_type_dispatch
¶
Extend a Pydantic model to add a 'type' field that is used as a discriminator field to dynamically determine the subtype that when deserializing models.
This allows automatic resolution to subtypes of the decorated model.
If a type field already exists, it should be a string literal field that has a constant value for each subclass. The default value of this field will be used as the dispatch key.
If a type field does not exist, one will be added. In this case, the value of the
field will be set to the value of the __dispatch_key__
. The base class should
define a __dispatch_key__
class method that is used to determine the unique key
for each subclass. Alternatively, each subclass can define the __dispatch_key__
as a string literal.
The base class must not define a 'type' field. If it is not desirable to add a field
to the model and the dispatch key can be tracked separately, the lower level
utilities in prefect.utilities.dispatch
should be used directly.
Source code in prefect/utilities/pydantic.py
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get_class_fields_only
¶
Gets all the field names defined on the model class but not any parent classes. Any fields that are on the parent but redefined on the subclass are included.
Source code in prefect/utilities/pydantic.py
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