Router prefix and tags in FastAPI - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a router with prefix '/items'.

FastAPI

from fastapi import APIRouter

router = APIRouter(prefix=[1])

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

A'items/'

B"/items"

C"items"

D'/item'

Attempts:

3 left

💡 Hint

Common Mistakes

Omitting the leading slash in the prefix string.

Using singular form instead of plural for resource path.

The prefix must start with a slash and match the route base path, so '/items' is correct.

2fill in blank

medium

Complete the code to add tags to the router for documentation.

FastAPI

router = APIRouter(prefix="/users", tags=[1])

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

A["user"]

B"users"

C["users"]

D"user"

Attempts:

3 left

💡 Hint

Common Mistakes

Passing a single string instead of a list.

Using singular form 'user' instead of plural 'users' for tags.

Tags must be a list of strings, so ["users"] is correct.

3fill in blank

hard

Fix the error in the router creation by completing the blank.

FastAPI

router = APIRouter(prefix=[1], tags=["items"])

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

A"/items"

Bitems

C'items/'

D"items"

Attempts:

3 left

💡 Hint

Common Mistakes

Using unquoted identifiers instead of strings.

Missing the leading slash in the prefix string.

The prefix must be a string starting with a slash, so "/items" is correct.

4fill in blank

hard

Fill both blanks to create a router with prefix '/products' and tags ['products', 'inventory'].

FastAPI

router = APIRouter(prefix=[1], tags=[2])

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

A"/products"

B["products", "inventory"]

C["product", "stock"]

D"products"

Attempts:

3 left

💡 Hint

Common Mistakes

Using tags as a single string instead of a list.

Missing the leading slash in prefix.

The prefix must be '/products' as a string, and tags must be a list of strings including 'products' and 'inventory'.

5fill in blank

hard

Fill all three blanks to create a router with prefix '/orders', tags ['orders'], and include a GET endpoint '/list'.

FastAPI

router = APIRouter(prefix=[1], tags=[2])

@router.get([3])
async def list_orders():
    return {"message": "List of orders"}

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

A"/orders"

B["orders"]

C"/list"

D"list"

Attempts:

3 left

💡 Hint

Common Mistakes

Omitting the leading slash in prefix or path.

Using tags as a string instead of a list.

The prefix is '/orders', tags is a list with 'orders', and the GET path must be '/list' with quotes.

Practice

1. What is the main purpose of using a prefix in a FastAPI router?

easy

A. To add authentication to routes automatically

B. To group routes under a common URL path segment

C. To change the HTTP method of all routes

D. To disable routes temporarily

Solution

1. Step 1: Understand what prefix does in FastAPI routers

   The prefix adds a common path segment to all routes defined in that router, grouping them logically.

2. Step 2: Compare options with prefix purpose

   Only To group routes under a common URL path segment correctly describes grouping routes under a shared URL path segment.

3. Final Answer:

   To group routes under a common URL path segment -> Option B

4. Quick Check:

   Router prefix = group routes [OK]

Hint: Prefix groups routes by URL path segment [OK]

Common Mistakes:

• Thinking prefix changes HTTP methods
• Confusing prefix with authentication
• Assuming prefix disables routes

2. Which of the following is the correct way to add a prefix and tags to a FastAPI router?

easy

A. router = APIRouter(prefix='/items', tags=['items'])

B. router = APIRouter(tags='/items', prefix=['items'])

C. router = APIRouter(prefix=['items'], tags='/items')

D. router = APIRouter(prefix='/items', tags='/items')

Solution

1. Step 1: Recall correct parameter types for prefix and tags

   Prefix expects a string starting with '/', tags expects a list of strings.

2. Step 2: Check each option's syntax

   router = APIRouter(prefix='/items', tags=['items']) uses prefix as string and tags as list correctly; others mix types incorrectly.

3. Final Answer:

   router = APIRouter(prefix='/items', tags=['items']) -> Option A

4. Quick Check:

   Prefix string + tags list = correct syntax [OK]

Hint: Prefix is string, tags is list of strings [OK]

Common Mistakes:

• Using list for prefix instead of string
• Using string for tags instead of list
• Mixing order of parameters incorrectly

3. Given this code snippet, what is the full path of the endpoint?

from fastapi import APIRouter

router = APIRouter(prefix='/users', tags=['users'])

@router.get('/profile')
async def get_profile():
    return {'msg': 'User profile'}

medium

A. /profile/users

B. /profile

C. /users

D. /users/profile

Solution

1. Step 1: Identify router prefix and route path

   The router has prefix '/users' and the route path is '/profile'.

2. Step 2: Combine prefix and route path

   Full path is prefix + route path = '/users' + '/profile' = '/users/profile'.

3. Final Answer:

   /users/profile -> Option D

4. Quick Check:

   Prefix + route path = full endpoint path [OK]

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

Common Mistakes:

• Ignoring prefix and using only route path
• Swapping prefix and route path order
• Confusing tags with path

4. What is wrong with this FastAPI router code?

router = APIRouter(prefix=['/items'], tags='items')

medium

A. prefix should be a list, tags should be a string

B. Both prefix and tags should be strings

C. prefix should be a string, tags should be a list of strings

D. No error, this is valid syntax

Solution

1. Step 1: Check expected types for prefix and tags

   Prefix must be a string starting with '/', tags must be a list of strings.

2. Step 2: Analyze given code

   Prefix is given as a list, tags as a string, both reversed from expected types.

3. Final Answer:

   prefix should be a string, tags should be a list of strings -> Option C

4. Quick Check:

   Prefix = string, tags = list [OK]

Hint: Prefix string, tags list; reverse causes error [OK]

Common Mistakes:

• Using list for prefix
• Using string for tags
• Assuming both can be strings

5. You want to create two routers in FastAPI: one for /products tagged 'products' and another for /orders tagged 'orders'. How do you correctly set prefixes and tags to keep your API organized?

hard

A. router_products = APIRouter(prefix='/products', tags=['products'])\nrouter_orders = APIRouter(prefix='/orders', tags=['orders'])

B. router_products = APIRouter(prefix=['products'], tags='products')\nrouter_orders = APIRouter(prefix=['orders'], tags='orders')

C. router_products = APIRouter(prefix='/products', tags='products')\nrouter_orders = APIRouter(prefix='/orders', tags='orders')

D. router_products = APIRouter(tags=['products'])\nrouter_orders = APIRouter(prefix='/orders')

Solution

1. Step 1: Recall correct types for prefix and tags

   Prefix must be a string starting with '/', tags must be a list of strings.

2. Step 2: Evaluate each option for correctness and organization

   router_products = APIRouter(prefix='/products', tags=['products'])\nrouter_orders = APIRouter(prefix='/orders', tags=['orders']) correctly assigns string prefixes and list tags for both routers, organizing API paths and documentation clearly.

3. Final Answer:

   router_products = APIRouter(prefix='/products', tags=['products']) router_orders = APIRouter(prefix='/orders', tags=['orders']) -> Option A

4. Quick Check:

   Correct prefix and tags keep API organized [OK]

Hint: Use string prefix and list tags for each router [OK]

Common Mistakes:

• Using list for prefix or string for tags
• Omitting prefix or tags on one router
• Mixing tags and prefix types