[Solved] Given this code, what will be the response when calling GET /items/42?... Given this code, what will be the response when calling GET /items/42? | FastAPI

FastAPI - Dependency Injection

Given this code, what will be the response when calling GET /items/42?

from fastapi import FastAPI, Depends

app = FastAPI()

class ItemDependency:
    async def __call__(self, item_id: int):
        return f"Item ID is {item_id}"

@app.get('/items/{item_id}')
async def read_item(dep: str = Depends(ItemDependency())):
    return {"message": dep}

A{"message": "Item ID is dep"}

B{"message": "Item ID is 42"}

CRuntime error due to missing parameter

D{"message": "42"}

Step-by-Step Solution

Solution:

Step 1: Understand dependency injection with parameters
ItemDependency's __call__ accepts item_id, which FastAPI injects from path parameter.
Step 2: Analyze endpoint return
The dependency returns 'Item ID is 42', which is returned in JSON message.
Final Answer:
{"message": "Item ID is 42"} -> Option B
Quick Check:
Dependency returns formatted string = B [OK]

Quick Trick: Dependencies can receive path params automatically [OK]

Common Mistakes:

MISTAKES

Assuming dependency returns parameter name instead of value
Expecting runtime error due to parameter
Confusing dependency return with raw parameter

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Given this code, what will be the response when calling GET /items/42?

Step 1: Understand dependency injection with parameters

Step 2: Analyze endpoint return

Final Answer:

Quick Check:

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