How to parse and read "_id" field from and to a pydantic model?

Question

I am trying to parse MongoDB data to a pydantic schema but fail to read its _id field which seem to just disappear from the schema.
The issue is definitely related to the underscore in front of the object attribute. I can't change _id field name since that would imply not parsing the field at all.
Please find below the code I use (using int instead of ObjectId for the sake of simplification)

from pydantic import BaseModel

class User_1(BaseModel):
    _id: int

data_1 = {"_id": 1}

parsed_1 = User_1(**data_1)
print(parsed_1.schema())

class User_2(BaseModel):
    id: int

data_2 = {"id": 1}

parsed_2 = User_2(**data_2)
print(parsed_2.schema())

User_1 is parsed successfully since its _id field is required but can't be read afterwards. User_2 works in the above example by fails if attached to Mongo which doesn't provide any id field but _id.

Output of the code above reads as follows:

User_1  {'title': 'User_1', 'type': 'object', 'properties': {}}
User_2  {'title': 'User_2', 'type': 'object', 'properties': {'id': {'title': 'Id', 'type': 'integer'}}, 'required': ['id']}

Answer 1

you need to use an alias for that field name

from pydantic import BaseModel, Field

class User_1(BaseModel):
    id: int = Field(..., alias='_id')

See the docs here.