[Solved] You want to create a FastAPI endpoint to update an item only if it exists, otherwise return a 404 error.... Which code snippet correctly implements this behavior? | FastAPI

FastAPI - Database Integration

You want to create a FastAPI endpoint to update an item only if it exists, otherwise return a 404 error. Which code snippet correctly implements this behavior? A:

@app.put("/items/{item_id}")
async def update_item(item_id: int, item: dict):
    items[item_id] = item
    return item

B:

@app.put("/items/{item_id}")
async def update_item(item_id: int, item: dict):
    if item_id not in items:
        return {"error": "Not found"}
    items[item_id] = item
    return item

C:

from fastapi import HTTPException
@app.put("/items/{item_id}")
async def update_item(item_id: int, item: dict):
    if item_id not in items:
        raise HTTPException(status_code=404, detail="Item not found")
    items[item_id] = item
    return item

D:

@app.put("/items/{item_id}")
async def update_item(item_id: int, item: dict):
    try:
        items[item_id] = item
    except KeyError:
        return {"error": "Not found"}
    return item

ARaises HTTPException with 404 status if missing

BReturns error dict but no HTTP status code change

CUpdates without checking existence, no error if missing

DCatches KeyError incorrectly, since assignment won't raise it

Step-by-Step Solution

Solution:

Step 1: Understand proper 404 error handling in FastAPI
FastAPI uses HTTPException to return HTTP errors with status codes.
Step 2: Analyze each option's error handling
The snippet using HTTPException(status_code=404, detail="Item not found") correctly returns a 404 response. Others either update without checking (200 OK), return an error dict as 200 OK, or misuse try-except since assignment does not raise KeyError.
Final Answer:
Raises HTTPException with 404 status if missing -> Option A
Quick Check:
Use HTTPException for proper HTTP error responses [OK]

Quick Trick: Use HTTPException to return 404 errors in FastAPI [OK]

Common Mistakes:

MISTAKES

Returning error dict without HTTP status change
Assuming assignment raises KeyError
Not raising HTTPException for errors

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More FastAPI Quizzes

You want to create a FastAPI endpoint to update an item only if it exists, otherwise return a 404 error. Which code snippet correctly implements this behavior? A:

Step 1: Understand proper 404 error handling in FastAPI

Step 2: Analyze each option's error handling

Final Answer:

Quick Check:

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