Python [pydantic] - Date validation

Question

i'd like to valid a json input for dates as pydantic class, next, to simply inject the file to Mongo.

Simple class with date type

class CustomerBase(BaseModel):
    birthdate: date = None

Using motor for working with Mongo

Db configuration:

from motor.motor_asyncio import AsyncIOMotorClient

DB = DB_CLIENT[CONF.get("databases", dict())["mongo"]["NAME"]]

8/03/2021 - Update:

I did the following debug test, first print the class to see how it saved and next try to inject it to Mongo.

so for input:

{ "birthdate": "2021-03-05"}

Routing:

@customers_router.post("/", response_model=dict)
async def add_customer(customer: CustomerBase):
    print(customer.dict())

>> {'birthdate': datetime.date(2021, 3, 5)}

    await DB.customer.insert_one(customer.dict())
    return {"test":1}

>> 
 File "./customers/routes.py", line 74, in add_customer
    await DB.customer.insert_one(customer.dict())
  File "/usr/local/lib/python3.8/concurrent/futures/thread.py", line 57, in run
    result = self.fn(*self.args, **self.kwargs)
  File "/usr/local/lib/python3.8/site-packages/pymongo/collection.py", line 698, in insert_one
    self._insert(document,
  File "/usr/local/lib/python3.8/site-packages/pymongo/collection.py", line 613, in _insert
    return self._insert_one(
  File "/usr/local/lib/python3.8/site-packages/pymongo/collection.py", line 602, in _insert_one
    self.__database.client._retryable_write(
  File "/usr/local/lib/python3.8/site-packages/pymongo/mongo_client.py", line 1498, in _retryable_write
    return self._retry_with_session(retryable, func, s, None)
  File "/usr/local/lib/python3.8/site-packages/pymongo/mongo_client.py", line 1384, in _retry_with_session
    return self._retry_internal(retryable, func, session, bulk)
  File "/usr/local/lib/python3.8/site-packages/pymongo/mongo_client.py", line 1416, in _retry_internal
    return func(session, sock_info, retryable)
  File "/usr/local/lib/python3.8/site-packages/pymongo/collection.py", line 590, in _insert_command
    result = sock_info.command(
  File "/usr/local/lib/python3.8/site-packages/pymongo/pool.py", line 699, in command
    self._raise_connection_failure(error)
  File "/usr/local/lib/python3.8/site-packages/pymongo/pool.py", line 683, in command
    return command(self, dbname, spec, slave_ok,
  File "/usr/local/lib/python3.8/site-packages/pymongo/network.py", line 120, in command
    request_id, msg, size, max_doc_size = message._op_msg(
  File "/usr/local/lib/python3.8/site-packages/pymongo/message.py", line 714, in _op_msg
    return _op_msg_uncompressed(
bson.errors.InvalidDocument: cannot encode object: datetime.date(2021, 3, 5), of type: <class 'datetime.date'>

Issues: 1.The date in class saved as birthday: datetime.date(2021, 3, 5) is that expected? 2.Surely the problem coming from: ''' DB.customer.insert_one(customer.dict()) ''' it does work when i change the date type to str in Class

Update 09/03/2022:

following Tom's suggestion: the decorator and parse_birthday function added. Now i able to document to Mongo but not able to read it.

class CustomerBase(BaseModel):
    birthdate: datetime.date

    @validator("birthdate", pre=True)
    def parse_birthdate(cls, value):
        return datetime.datetime.strptime(
            value,
            "%d/%m/%Y"
        ).date()

    def dict(self, *args, **kwargs) -> 'DictStrAny':
        for_mongo = kwargs.pop('for_mongo', False)
        d = super().dict(*args, **kwargs)
        if for_mongo:
            for k, v in d.items():
                if isinstance(v, datetime.date):
                    d[k] = datetime.datetime(
                        year=v.year,
                        month=v.month,
                        day=v.day,
                    )
        return d

class CustomerOnDB(CustomerBase):
    id_: str

assign data (working): input: {"birthdate": "01/11/1978"}

@customers_router.post("/", response_model=dict )
async def add_customer(customer: CustomerBase):

    customer_op = await DB.customer.insert_one(customer.dict(for_mongo=True))
    if customer_op.inserted_id:
        #customer_op.inserted_id -> is the str _id
        await _get_customer_or_404(customer_op.inserted_id)
        return { "id_": str(customer_op.inserted_id) }

When trying to read:

def validate_object_id(id_: str):
    try:
        _id = ObjectId(id_)
    except Exception:
        raise HTTPException(status_code=400)
    return _id


@customers_router.get(
    "/{id_}",
    response_model=CustomerOnDB
)
async def get_customer_by_id(id_: ObjectId = Depends(validate_object_id)):
    customer = await DB.customer.find_one({"_id": id_})
    if customer:
        customer["id_"] = str(customer["_id"])
        return customer
    else:
        raise HTTPException(status_code=404, detail="Customer not found")

Getting:

  File "/usr/local/lib/python3.8/site-packages/fastapi/routing.py", line 126, in serialize_response
    raise ValidationError(errors, field.type_)
pydantic.error_wrappers.ValidationError: 1 validation error for CustomerOnDB
response -> 0 -> birthdate
  strptime() argument 1 must be str, not datetime.datetime (type=type_error)

Answer 1

I'm not sure what your question is as your CustomerBase works fine with

{ "birthdate": "2021-03-05"} this input.

If you want to parse %d/%m/%Y date, parse it using validator and pre parameter.

class CustomerBase(BaseModel):
    birthdate: date

    @validator("birthdate", pre=True)
    def parse_birthdate(cls, value):
        return datetime.datetime.strptime(
            value,
            "%d/%m/%Y"
        ).date()

EDIT: You added a comment mentioning something else that doesn't work as you expect. AFAIK mongo doesn't accept datetime.date . Just change it to datetime.datetime when dumping to dict or change type to datetime .

example

import datetime

from pydantic.main import BaseModel


class CustomerBase(BaseModel):
    birthdate: datetime.date

    def dict(self, *args, **kwargs) -> 'DictStrAny':
        d = super().dict(*args, **kwargs)
        for k, v in d.items():
            if isinstance(v, datetime.date):
                d[k] = datetime.datetime(
                    year=v.year,
                    month=v.month,
                    day=v.day,
                )
        return d

If you need both functionalities

import datetime

from pydantic import validator
from pydantic.main import BaseModel


class CustomerBase(BaseModel):
    birthdate: datetime.date

    @validator("birthdate", pre=True)
    def parse_birthdate(cls, value):
        return datetime.datetime.strptime(
            value,
            "%d/%m/%Y"
        ).date()

    def dict(self, *args, **kwargs) -> 'DictStrAny':
        for_mongo = kwargs.pop('for_mongo', False)
        d = super().dict(*args, **kwargs)
        if for_mongo:
            for k, v in d.items():
                if isinstance(v, datetime.date):
                    d[k] = datetime.datetime(
                        year=v.year,
                        month=v.month,
                        day=v.day,
                    )
        return d


>>> c = CustomerBase(**{"birthdate": "03/05/2021"})
>>> c.dict()
>>> {'birthdate': datetime.date(2021, 5, 3)}
>>> c.dict(for_mongo=True)
>>> {'birthdate': datetime.datetime(2021, 5, 3, 0, 0)}