[Solved] Given the code below, what will be the output when accessing /items/42?... Given the code below, what will be the output when accessing /items/42? | FastAPI

FastAPI - Dependency Injection

Given the code below, what will be the output when accessing /items/42?

from fastapi import FastAPI, Depends

app = FastAPI()

def common_dep():
    return "shared value"

@app.get('/items/{item_id}')
def read_item(item_id: int, value: str = Depends(common_dep)):
    return {"item_id": item_id, "value": value}

AError: Missing required parameter 'value'

B{"item_id": 42, "value": 42}

C{"item_id": 42, "value": null}

D{"item_id": 42, "value": "shared value"}

Step-by-Step Solution

Solution:

Step 1: Understand dependency injection
The function common_dep returns the string "shared value". FastAPI injects this into the value parameter via Depends(common_dep).
Step 2: Check the returned JSON
The route returns a dictionary with item_id from the path and value from the dependency. So the output will be {"item_id": 42, "value": "shared value"}.
Final Answer:
{"item_id": 42, "value": "shared value"} -> Option D
Quick Check:
Dependency injects "shared value" [OK]

Quick Trick: Depends injects return value as parameter [OK]

Common Mistakes:

MISTAKES

Assuming dependency returns item_id
Expecting error due to missing parameter
Thinking value will be null without explicit call

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Given the code below, what will be the output when accessing /items/42?

Step 1: Understand dependency injection

Step 2: Check the returned JSON

Final Answer:

Quick Check:

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