Sub-dependencies in FastAPI - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a simple dependency function in FastAPI.

FastAPI

from fastapi import Depends, FastAPI

app = FastAPI()

def common_parameters():
    return {"q": "fastapi"}

@app.get("/items/")
async def read_items(params: dict = Depends([1])):
    return params

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

Acommon_parameters

BDepends

CFastAPI

Dread_items

Attempts:

3 left

💡 Hint

Common Mistakes

Passing Depends instead of the function name.

Passing the FastAPI app instance.

Using the endpoint function name as dependency.

The dependency function common_parameters is passed to Depends() to inject its return value.

2fill in blank

medium

Complete the code to declare a sub-dependency function that depends on another dependency.

FastAPI

from fastapi import Depends, FastAPI

app = FastAPI()

def common_parameters():
    return {"q": "fastapi"}

def query_extractor(params: dict = Depends([1])):
    return params.get("q")

@app.get("/search/")
async def search(q: str = Depends(query_extractor)):
    return {"query": q}

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

AFastAPI

Bcommon_parameters

Csearch

Dquery_extractor

Attempts:

3 left

💡 Hint

Common Mistakes

Using the sub-dependency function itself inside Depends().

Passing the endpoint function name as dependency.

Passing the FastAPI app instance.

The sub-dependency query_extractor depends on common_parameters to get the parameters dictionary.

3fill in blank

hard

Fix the error in the sub-dependency declaration by completing the blank.

FastAPI

from fastapi import Depends, FastAPI

app = FastAPI()

def common_parameters():
    return {"q": "fastapi"}

def query_extractor(params: dict = Depends([1])):
    return params.get("q")

@app.get("/items/")
async def read_items(q: str = Depends(query_extractor)):
    return {"query": q}

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

Aread_items

Bquery_extractor

Ccommon_parameters

DFastAPI

Attempts:

3 left

💡 Hint

Common Mistakes

Referencing the sub-dependency itself inside Depends().

Using the endpoint function name inside Depends().

The sub-dependency query_extractor must depend on common_parameters to receive the parameters dictionary.

4fill in blank

hard

Fill both blanks to create a sub-dependency that extracts a header and then use it in the endpoint.

FastAPI

from fastapi import Depends, FastAPI, Header

app = FastAPI()

def user_agent_header(user_agent: str = [1]):
    return user_agent

@app.get("/headers/")
async def read_headers(user_agent: str = Depends([2])):
    return {"User-Agent": user_agent}

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

AHeader("User-Agent")

Buser_agent_header

CDepends(user_agent_header)

DHeader

Attempts:

3 left

💡 Hint

Common Mistakes

Using Depends() inside the sub-dependency parameter default.

Passing Depends(user_agent_header) instead of the function name in the endpoint.

The sub-dependency user_agent_header uses Header("User-Agent") to extract the header value. The endpoint depends on user_agent_header.

5fill in blank

hard

Fill all three blanks to create nested dependencies where the endpoint depends on a sub-dependency that depends on another dependency.

FastAPI

from fastapi import Depends, FastAPI

app = FastAPI()

def common_parameters():
    return {"token": "abc123"}

def verify_token(params: dict = Depends([1])):
    token = params.get([2])
    if token != "abc123":
        raise Exception("Invalid token")
    return token

@app.get("/secure-data/")
async def secure_data(token: str = Depends([3])):
    return {"token": token}

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

Acommon_parameters

B"token"

Cverify_token

Dsecure_data

Attempts:

3 left

💡 Hint

Common Mistakes

Using the endpoint function name inside Depends().

Using the wrong key string for the token.

Referencing the sub-dependency inside itself.

The sub-dependency verify_token depends on common_parameters to get the parameters dictionary. It extracts the token key. The endpoint depends on verify_token.