CODEWITHSUNDEEP
pythonpydantic
Himal Acharya
Himal Acharya

Reputation: 1006

Create pydantic model for Optional field with alias

Pydantic model for compulsory field with alias is created as follows

class MedicalFolderUpdate(RWModel):
    id : str = Field(alias='_id')
    university : Optional[str]

How to add optional field university's alias name 'school' as like of id?

Upvotes: 6

Views: 7919

Answers (3)

lcarvajal
lcarvajal

Reputation: 585

It is not documented on the Pydantic website how to use the typing Optional with the Fields Default besides their allowed types in which they include the mentioned Optional:

Optional[x] is simply shorthand for Union[x, None]; see Unions below for more detail on parsing and validation and Required Fields for details about required fields that can receive None as a value.

for that, you would have to use their field customizations as in the example:

class Figure(BaseModel):
    name: str = Field(alias='Name')
    edges: str = Field(default=None, alias='Edges')

without the default value, it breaks because the optional does not override that the field is required and needs a default value. Which is the solution I used to overcome this problem while using Pydantic with fast API to manage mongo resources

Upvotes: 13

Vasili Kulakou
Vasili Kulakou

Reputation: 11

Try the following:

class MedicalFolderUpdate(RWModel):
    id : str = Field(alias='_id')
    university : Optional[str] = Field(alias='school')

Upvotes: 1

Yaakov Bressler
Yaakov Bressler

Reputation: 12008

In your case, you will want to use Pydantic's Field function to specify the info for your optional field. Also, must enable population fields by alias by setting allow_population_by_field_name in the model Config:

from typing import Optional


class MedicalFolderUpdate(BaseModel):
    id: str = Field(alias='_id')
    university: Optional[str] = Field(alias="school")

    class Config:
        allow_population_by_field_name = True

By default, value for university will be None. If you want to exclude unset values, you can do so when serializing to json or dict like so:

raw_data = {"id": "abc"}
row = MedicalFolderUpdate.parse_obj(raw_data)

# default, university is None
print(row.dict())  # {'id': 'abc', 'university': None}

# exclude from serialization
print(row.dict(exclude_unset=True))  # {'id': 'abc'}

Upvotes: 0

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