APIRouter for modular routes in FastAPI - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to import APIRouter from FastAPI.

FastAPI

from fastapi import [1]

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

ADepends

BFastAPI

CRequest

DAPIRouter

Attempts:

3 left

💡 Hint

Common Mistakes

Importing FastAPI instead of APIRouter

Using Request or Depends which are unrelated here

You import APIRouter from FastAPI to create modular route groups.

2fill in blank

medium

Complete the code to create a new APIRouter instance.

FastAPI

router = [1]()

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

AAPIRouter

BFastAPI

CDepends

DRequest

Attempts:

3 left

💡 Hint

Common Mistakes

Trying to create FastAPI instance instead of APIRouter

Using Depends or Request which are not constructors

You create a router by calling APIRouter().

3fill in blank

hard

Fix the error in the route decorator to use the router instead of app.

FastAPI

@[1].get("/items")
async def read_items():
    return [{"item_id": "foo"}]

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

Aapp

BDepends

Crouter

DFastAPI

Attempts:

3 left

💡 Hint

Common Mistakes

Using @app.get instead of @router.get

Using FastAPI or Depends in decorator

Routes in modular files use the router instance, not the main app.

4fill in blank

hard

Fill both blanks to include the router in the main FastAPI app.

FastAPI

from fastapi import FastAPI

app = FastAPI()
app.[1](router, prefix=[2])

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

Ainclude_router

Badd_route

C"/api"

D"/items"

Attempts:

3 left

💡 Hint

Common Mistakes

Using add_route which is not for routers

Wrong prefix string or missing quotes

You add modular routes to the main app using include_router with a prefix path.

5fill in blank

hard

Fill all three blanks to define a router with a GET route and include it in the app with prefix.

FastAPI

from fastapi import FastAPI, [1]

router = [1]()

@router.get("/hello")
async def say_hello():
    return {"message": "Hello"}

app = FastAPI()
app.[2](router, prefix=[3])

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

AAPIRouter

Binclude_router

C"/greet"

DFastAPI

Attempts:

3 left

💡 Hint

Common Mistakes

Using FastAPI instead of APIRouter for router

Wrong method name to include router

Missing quotes around prefix

This shows the full pattern: import APIRouter, create router, define route, then include router in app with prefix.

Practice

1. What is the main purpose of using APIRouter in a FastAPI application?

easy

A. To replace the main FastAPI app instance

B. To handle background tasks

C. To automatically generate database models

D. To organize routes into smaller, manageable groups

Solution

1. Step 1: Understand APIRouter's role

   APIRouter is designed to group related routes together for better organization.

2. Step 2: Compare with other options

   It does not replace the main app, generate models, or handle background tasks.

3. Final Answer:

   To organize routes into smaller, manageable groups -> Option D

4. Quick Check:

   APIRouter groups routes = B [OK]

Hint: APIRouter groups routes for cleaner code [OK]

Common Mistakes:

• Thinking APIRouter replaces FastAPI app
• Confusing APIRouter with database tools
• Assuming APIRouter handles tasks beyond routing

2. Which of the following is the correct way to include a router with a prefix in a FastAPI app?

easy

A. app.include_router(router, prefix='/items')

B. app.add_router(router, prefix='/items')

C. app.include_router(router, path='/items')

D. app.register_router(router, prefix='/items')

Solution

1. Step 1: Recall the method to add routers

   The correct method is include_router() with a prefix argument.

2. Step 2: Check method names and parameters

   Only include_router() with prefix is valid; others are incorrect method names or parameters.

3. Final Answer:

   app.include_router(router, prefix='/items') -> Option A

4. Quick Check:

   Use include_router with prefix = A [OK]

Hint: Use include_router() with prefix to add routes [OK]

Common Mistakes:

• Using wrong method names like add_router or register_router
• Using 'path' instead of 'prefix' argument
• Forgetting to include the router at all

3. Given this code snippet, what will be the URL path to access the read_users endpoint?

from fastapi import FastAPI, APIRouter

router = APIRouter()

@router.get('/users')
async def read_users():
    return {'users': ['Alice', 'Bob']}

app = FastAPI()
app.include_router(router, prefix='/api')

medium

A. /users

B. /users/api

C. /api/users

D. /api

Solution

1. Step 1: Identify the route path in the router

   The route is defined as /users inside the router.

2. Step 2: Check the prefix used when including the router

   The router is included with prefix /api, so the full path is /api/users.

3. Final Answer:

   /api/users -> Option C

4. Quick Check:

   Prefix + route path = /api/users [OK]

Hint: Full path = prefix + router path [OK]

Common Mistakes:

• Ignoring the prefix when accessing the route
• Confusing route path with prefix
• Assuming prefix replaces route path

4. What is wrong with this FastAPI router setup?

from fastapi import FastAPI, APIRouter

router = APIRouter()

@router.get('/items')
async def get_items():
    return ['item1', 'item2']

app = FastAPI()
app.include_router(router, prefix='/')

@app.get('/items')
async def root_items():
    return ['root item']

medium

A. The prefix causes route conflict with root app route

B. APIRouter cannot be included with prefix

C. Router path must start with '/api'

D. The router function must be synchronous

Solution

1. Step 1: Analyze route paths

   The router has a route at /items and is included with prefix /, making its full path /items.

2. Step 2: Check for conflicts

   The main app also has a route at /items. This causes a direct route conflict.

3. Step 3: Identify the actual problem

   The prefix causes the router path to overlap with the root app route.

4. Final Answer:

   The prefix causes route conflict with root app route -> Option A

5. Quick Check:

   Prefix and root route clash = A [OK]

Hint: Avoid prefix same as root route path [OK]

Common Mistakes:

• Thinking APIRouter can't use prefix
• Assuming router paths must start with /api
• Believing async functions must be sync

5. You want to create two routers: one for user routes with prefix /users and one for item routes with prefix /items. How should you include them in your FastAPI app to avoid route conflicts and keep code modular?

hard

A. Define all routes directly in the main FastAPI app without routers

B. Create two APIRouter instances, define routes, then include both with their prefixes in the main app

C. Create one APIRouter with all routes and include it without prefixes

D. Use one APIRouter and change prefixes dynamically inside route functions

Solution

1. Step 1: Understand modular routing

   Using separate APIRouter instances for users and items keeps routes organized and modular.

2. Step 2: Include routers with distinct prefixes

   Including each router with its own prefix (/users and /items) avoids conflicts and clarifies URLs.

3. Step 3: Avoid other options

   Single router or no routers reduce modularity; dynamic prefix changes are not standard practice.

4. Final Answer:

   Create two APIRouter instances, define routes, then include both with their prefixes in the main app -> Option B

5. Quick Check:

   Separate routers + prefixes = modular, no conflicts [OK]

Hint: Use separate routers with prefixes for modularity [OK]

Common Mistakes:

• Putting all routes in one router without prefixes
• Defining routes only in main app losing modularity
• Trying to change prefixes inside route functions