[QUESTION] Getting Validation Error on Response, using Alchemysql + FastAPI

Description

i’m getting a validation error on my API, not sure what’s wrong with it, i followed the example at SQL (Relational) Databases i think it’s a problem with the pydantic models, i’m still not sure if defining it correctly.

here’s the package version that i’m using

• fastapi 0.63.0
• pydantic 1.7.3
• SQLAlchemy 1.3.22

here’s the error Traceback

2021-01-12 20:38:26,463 INFO sqlalchemy.engine.base.Engine BEGIN (implicit)
2021-01-12 20:38:26,464 INFO sqlalchemy.engine.base.Engine SELECT device.id AS device_id, device.macaddress AS device_macaddress, device.name AS device_name
FROM device
2021-01-12 20:38:26,465 INFO sqlalchemy.engine.base.Engine ()
2021-01-12 20:38:26,478 INFO sqlalchemy.engine.base.Engine SELECT record.id AS record_id, record.timestamp AS record_timestamp, record.image AS record_image, record.reading AS record_reading, record.device_id AS record_device_id
FROM record
WHERE ? = record.device_id
2021-01-12 20:38:26,479 INFO sqlalchemy.engine.base.Engine (1,)
2021-01-12 20:38:26,481 INFO sqlalchemy.engine.base.Engine SELECT record.id AS record_id, record.timestamp AS record_timestamp, record.image AS record_image, record.reading AS record_reading, record.device_id AS record_device_id
FROM record
WHERE ? = record.device_id
2021-01-12 20:38:26,482 INFO sqlalchemy.engine.base.Engine (2,)
INFO:     127.0.0.1:64156 - "GET /devices/ HTTP/1.1" 500 Internal Server Error
2021-01-12 20:38:26,484 INFO sqlalchemy.engine.base.Engine ROLLBACK
ERROR:    Exception in ASGI application
Traceback (most recent call last):
  File "e:\repo\tubes iot\env\lib\site-packages\uvicorn\protocols\http\h11_impl.py", line 394, in run_asgi
    result = await app(self.scope, self.receive, self.send)
  File "e:\repo\tubes iot\env\lib\site-packages\uvicorn\middleware\proxy_headers.py", line 45, in __call__
    return await self.app(scope, receive, send)
  File "e:\repo\tubes iot\env\lib\site-packages\fastapi\applications.py", line 199, in __call__
    await super().__call__(scope, receive, send)
  File "e:\repo\tubes iot\env\lib\site-packages\starlette\applications.py", line 111, in __call__
    await self.middleware_stack(scope, receive, send)
  File "e:\repo\tubes iot\env\lib\site-packages\starlette\middleware\errors.py", line 181, in __call__
    raise exc from None
  File "e:\repo\tubes iot\env\lib\site-packages\starlette\middleware\errors.py", line 159, in __call__
    await self.app(scope, receive, _send)
  File "e:\repo\tubes iot\env\lib\site-packages\starlette\exceptions.py", line 82, in __call__
    raise exc from None
  File "e:\repo\tubes iot\env\lib\site-packages\starlette\exceptions.py", line 71, in __call__
    await self.app(scope, receive, sender)
  File "e:\repo\tubes iot\env\lib\site-packages\starlette\routing.py", line 566, in __call__
    await route.handle(scope, receive, send)
  File "e:\repo\tubes iot\env\lib\site-packages\starlette\routing.py", line 227, in handle
    await self.app(scope, receive, send)
  File "e:\repo\tubes iot\env\lib\site-packages\starlette\routing.py", line 41, in app
    response = await func(request)
  File "e:\repo\tubes iot\env\lib\site-packages\fastapi\routing.py", line 209, in app
    response_data = await serialize_response(
  File "e:\repo\tubes iot\env\lib\site-packages\fastapi\routing.py", line 126, in serialize_response
    raise ValidationError(errors, field.type_)
pydantic.error_wrappers.ValidationError: 4 validation errors for Device
response -> 0 -> maccaddress
  field required (type=value_error.missing)
response -> 0 -> records -> 0 -> reading
  none is not an allowed value (type=type_error.none.not_allowed)
response -> 0 -> records -> 1 -> reading
  none is not an allowed value (type=type_error.none.not_allowed)
response -> 1 -> maccaddress
  field required (type=value_error.missing)

schemas.py

from typing import List, Optional
from pydantic import BaseModel

import datetime
class Record(BaseModel):
    id : int
    timestamp : datetime.datetime
    image : Optional[str]
    device_id : int
    reading : int

    class Config :
        orm_mode= True

class Device(BaseModel):
    id : int
    maccaddress : str
    name : Optional[str] = None
    records : List[Record] =[]

    class Config : 
        orm_mode = True
class DeviceChange(Device):
    name : str

models.py

class Device(Base):
    __tablename__ = 'device'
    id = Column(Integer, primary_key=True)
    macaddress = Column(String, unique=True)
    name = Column(String)

    records = relationship("Record",back_populates='device')

class Record(Base):
    __tablename__ = 'record'
    id = Column(Integer, primary_key=True)
    timestamp = Column(DateTime(timezone=False),default=func.now())
    image = Column(String) 
    reading = Column(Integer)
    device_id = Column(Integer, ForeignKey('device.id'))
    
    device = relationship("Device",back_populates='records')

crud.py

from sqlalchemy.orm import Session
import models, schemas, datetime

def get_devices(db : Session) : 
    return db.query(models.Device).all()

def get_device(db : Session, dev_id : int) :
    return db.query(models.Device).filter(models.Device.id == dev_id).first()

def get_records(db : Session, date: datetime, dev_id : int) : 
    return db.query(models.Record).filter(
        (models.Record.timestamp.like('%'+date+'%')),
        (models.Record.device_id == dev_id)
    ).all()

def set_name(db : Session, name : str, dev_id : int):
    query = db.query(models.Device).filter(
        models.Device.id == dev_id
    ).first()
    query.name = name
    db.commit()
    return query

main.py

app = FastAPI()

# Dependency
def get_db():
    db = SessionLocal()
    try:
        yield db
    finally:
        db.close()
# Return all Devices
@app.get("/devices/", response_model=List[schemas.Device])
def read_devices(db : Session = Depends(get_db)):
    devices = crud.get_devices(db)
    return devices

# Return Device 
@app.get("/devices/{device_id}", response_model=schemas.Device)
def read_device(device_id : int,db : Session = Depends(get_db)):
    device = crud.get_device(db,device_id)
    return device

# Return device records list
@app.get("/devices/{device_id}/records/{date}", response_model=List[schemas.Record])
def read_records(date : datetime.datetime, device_id : int, db : Session = Depends(get_db)):
    records = crud.get_records(db,date,device_id)
    return records

# Return Device latest record
@app.get("/devices/{device_id}/records/latest", response_model=schemas.Record)
def read_latest(device_id : int, db : Session = Depends(get_db)):
    record = crud.get_latest(db,device_id)
    return record.reading

[GagahGK]

Update : i fixed the problem by changing the pydantic variable in Record Class to optional

class Record(BaseModel):
    id : int
    timestamp : datetime.datetime
    image : Optional[str]
    device_id : int
    reading : Optional[int]

    class Config :
        orm_mode= True

thanks everyone i’m really sorry for creating stupid issues like this

[tiangolo]

Thanks for the help here everyone! 👏 🙇

Thanks for reporting back and closing the issue 👍

Sorry for the long delay! 🙈 I wanted to personally address each issue/PR and they piled up through time, but now I’m checking each one in order.