OAuth2 password flow in FastAPI - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to import the OAuth2PasswordBearer class from FastAPI.

FastAPI

from fastapi.security import [1]

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AAPIKeyHeader

BOAuth2PasswordRequestForm

COAuth2PasswordBearer

DHTTPBasic

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing OAuth2PasswordBearer with OAuth2PasswordRequestForm.

Importing HTTPBasic instead of OAuth2PasswordBearer.

The OAuth2PasswordBearer class is used to define the OAuth2 password flow token URL in FastAPI.

2fill in blank

medium

Complete the code to create an OAuth2PasswordBearer instance with the token URL '/token'.

FastAPI

oauth2_scheme = OAuth2PasswordBearer(tokenUrl=[1])

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A"/login"

B"/access"

C"/auth"

D"/token"

Attempts:

3 left

💡 Hint

Common Mistakes

Using '/login' or other URLs that do not match the token endpoint.

Forgetting to put quotes around the URL string.

The tokenUrl parameter should point to the URL where the client sends username and password to get the token. Commonly, this is '/token'.

3fill in blank

hard

Fix the error in the dependency injection to get the token from the OAuth2 scheme.

FastAPI

async def read_items(token: str = [1]):

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Aoauth2_scheme()

BDepends(oauth2_scheme)

CDepends(oauth2_scheme())

Doauth2_scheme

Attempts:

3 left

💡 Hint

Common Mistakes

Calling the oauth2_scheme inside Depends, which causes an error.

Not using Depends at all.

When using FastAPI dependencies, you pass the callable without parentheses to Depends. So it should be Depends(oauth2_scheme).

4fill in blank

hard

Fill both blanks to define a token endpoint that uses OAuth2PasswordRequestForm and returns a token.

FastAPI

from fastapi import FastAPI, Depends
from fastapi.security import OAuth2PasswordRequestForm

app = FastAPI()

@app.post("/token")
async def login(form_data: [1] = Depends()):
    return {"access_token": form_data.[2], "token_type": "bearer"}

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AOAuth2PasswordRequestForm

Busername

Cpassword

DOAuth2PasswordBearer

Attempts:

3 left

💡 Hint

Common Mistakes

Using OAuth2PasswordBearer instead of OAuth2PasswordRequestForm.

Accessing form_data.password instead of username for the token.

The OAuth2PasswordRequestForm dependency extracts form data including the username and password. The token response usually includes the username as the access token for demonstration.

5fill in blank

hard

Fill all three blanks to create a protected route that extracts the token and returns a welcome message.

FastAPI

from fastapi import FastAPI, Depends, HTTPException
from fastapi.security import OAuth2PasswordBearer

app = FastAPI()
oauth2_scheme = OAuth2PasswordBearer(tokenUrl="/token")

@app.get("/users/me")
async def read_users_me(token: str = Depends([1])):
    if not token:
        raise HTTPException(status_code=401, detail="Invalid authentication")
    return {"message": f"Welcome, [2]! Your token is [3]."}

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Aoauth2_scheme

Buser

Ctoken

DtokenUrl

Attempts:

3 left

💡 Hint

Common Mistakes

Using Depends(oauth2_scheme()) instead of Depends(oauth2_scheme).

Using tokenUrl instead of oauth2_scheme.

Using undefined variables in the message.

The dependency oauth2_scheme extracts the token. The welcome message uses a placeholder user (which could be replaced by username in real apps) and the token variable.