Custom exception handlers in FastAPI - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to import the correct FastAPI class.

FastAPI

from fastapi import [1]
app = [1]()

Drag options to blanks, or click blank then click option'

AResponse

BHTTPException

CRequest

DFastAPI

Attempts:

3 left

💡 Hint

Common Mistakes

Importing Request or Response instead of FastAPI

Trying to instantiate HTTPException as the app

The FastAPI class is imported to create the app instance.

2fill in blank

medium

Complete the code to define a custom exception handler for HTTPException.

FastAPI

@app.exception_handler([1])
async def http_exception_handler(request, exc):
    return JSONResponse(status_code=exc.status_code, content={"message": exc.detail})

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AException

BHTTPException

CResponse

DRequest

Attempts:

3 left

💡 Hint

Common Mistakes

Using Request or Response instead of HTTPException

Using the base Exception class which is too broad

The HTTPException class is used to catch HTTP errors in FastAPI.

3fill in blank

hard

Fix the error in the custom exception handler to return a JSON response.

FastAPI

from fastapi.responses import [1]

@app.exception_handler(ValueError)
async def value_error_handler(request, exc):
    return [1](status_code=400, content={"error": str(exc)})

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APlainTextResponse

BHTMLResponse

CJSONResponse

DRedirectResponse

Attempts:

3 left

💡 Hint

Common Mistakes

Using PlainTextResponse or HTMLResponse which do not send JSON

Forgetting to import JSONResponse

Use JSONResponse to send JSON content back to the client.

4fill in blank

hard

Fill both blanks to create a custom exception and handler that returns a JSON error message.

FastAPI

class CustomError(Exception):
    def __init__(self, message):
        self.message = message

@app.exception_handler([1])
async def custom_error_handler(request, exc):
    return JSONResponse(status_code=[2], content={"error": exc.message})

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ACustomError

B400

CHTTPException

D500

Attempts:

3 left

💡 Hint

Common Mistakes

Using HTTPException instead of CustomError in the handler decorator

Using wrong status code like 500

The handler catches CustomError and returns status code 400.

5fill in blank

hard

Fill all three blanks to raise a custom exception and handle it with a JSON response.

FastAPI

class MyException(Exception):
    def __init__(self, detail):
        self.detail = detail

@app.get("/error")
async def error_route():
    raise [1]("Something went wrong")

@app.exception_handler([2])
async def my_exception_handler(request, exc):
    return JSONResponse(status_code=[3], content={"error": exc.detail})

Drag options to blanks, or click blank then click option'

AMyException

BCustomError

C400

D500

Attempts:

3 left

💡 Hint

Common Mistakes

Raising a different exception than handled

Using status code 500 instead of 400

The route raises MyException, which is handled by the custom handler returning status 400.