Routes Manager for FastAPI

Standardize and handle exceptions in FastAPI more elegantly.

Installation

$ pip install fastapi-exceptionshandler

Example

from fastapi import FastAPI

from fastapi_exceptionshandler import APIExceptionMiddleware

app = FastAPI()

# Register the middleware
app.add_middleware(APIExceptionMiddleware, capture_unhandled=True)  # Capture all exceptions

# You can also capture Validation errors, that are not captured by default
from fastapi_exceptionshandler import APIExceptionHandler

from pydantic import ValidationError
app.add_exception_handler(ValidationError, APIExceptionHandler.unhandled)

from fastapi.exceptions import RequestValidationError
app.add_exception_handler(RequestValidationError, APIExceptionHandler.unhandled)

@app.get("/")
def read_root():
    return 1/0

Run it

$ uvicorn main:app --reload

Check it

Browse to http://127.0.0.1:8000 you should see this json:

{"errorCode": "InternalError", "message": "Internal Server Error"}

Creating custom exceptions

In order to create a custom exception you need to extend APIException and ErrorCodeBase classes.

Note: if you want to capture only APIException then don't send the capture_unhandled param, or set it to False

from fastapi import FastAPI

from fastapi_exceptionshandler import APIExceptionMiddleware, APIException, ErrorCodeBase

from starlette import status


app = FastAPI()

# Register the middleware
app.add_middleware(APIExceptionMiddleware)


class CustomException(APIException):
    status_code = status.HTTP_400_BAD_REQUEST
    
    class ErrorCode(ErrorCodeBase):
        CustomExceptionCode = "Custom Exception Message", status.HTTP_401_UNAUTHORIZED
        CustomExceptionCodeWithDefaultStatusCode = "Custom Exception Message"
        
        
@app.get("/")
def read_root():
    raise CustomException(CustomException.ErrorCode.CustomExceptionCode)

Then you should get a 401 response with this body

{"errorCode": "CustomExceptionCode", "message": "Custom Exception Message"}

Or you can handle exceptions manually...

@app.get("/")
def read_root():
    try:
        raise CustomException(CustomException.ErrorCode.CustomExceptionCode)
    except APIException as exc:
        return await APIExceptionHandler.handled(exc)
    except Exception as exc:  # Handle all exceptions
        return await APIExceptionHandler.unhandled(exc)

Note: The ErrorCode class doesn't need to be inside CustomException and can be shared with another exceptions as well.