Multiple query parameters in FastAPI - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a FastAPI GET endpoint that accepts two query parameters: 'name' and 'age'.

FastAPI

from fastapi import FastAPI
app = FastAPI()

@app.get("/user")
async def get_user(name: str, age: [1]):
    return {"name": name, "age": age}

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

Aint

Bfloat

Cstr

Dbool

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'str' for age which should be a number.

Forgetting to specify the type for the query parameter.

The 'age' parameter should be an integer, so we use int as its type.

2fill in blank

medium

Complete the code to make the 'age' query parameter optional with a default value of 18.

FastAPI

from fastapi import FastAPI
app = FastAPI()

@app.get("/user")
async def get_user(name: str, age: [1] = 18):
    return {"name": name, "age": age}

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

AOptional[int]

Bstr

Cint

Dfloat

Attempts:

3 left

💡 Hint

Common Mistakes

Using Optional[int] without importing Optional.

Not assigning a default value to make the parameter optional.

To make 'age' optional with a default, just assign a default value to the type int. Using Optional[int] requires importing Optional and is not necessary here.

3fill in blank

hard

Fix the error in the code to correctly accept multiple query parameters 'q' and 'limit'.

FastAPI

from fastapi import FastAPI
app = FastAPI()

@app.get("/search")
async def search(q: str, limit: [1] = 10):
    return {"query": q, "limit": limit}

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

Astr

Bint

Cbool

Dfloat

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'str' for 'limit' which should be a number.

Forgetting to assign a default value to 'limit'.

The 'limit' parameter should be an integer to specify how many results to return.

4fill in blank

hard

Fill both blanks to create a FastAPI endpoint that accepts a list of tags as query parameters.

FastAPI

from fastapi import FastAPI
from typing import [1]
app = FastAPI()

@app.get("/items")
async def get_items(tags: [2][str] = []):
    return {"tags": tags}

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

AList

BDict

CSet

DTuple

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'Dict' or 'Set' which are not ordered lists.

Not importing 'List' from typing.

To accept multiple query parameters as a list, import and use List from typing.

5fill in blank

hard

Fill all three blanks to create a FastAPI endpoint that accepts multiple optional query parameters with default values.

FastAPI

from fastapi import FastAPI
from typing import [1], [2]
app = FastAPI()

@app.get("/filter")
async def filter_items(categories: [1][[2][str]] = None, limit: [3] = 5):
    return {"categories": categories, "limit": limit}

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

AOptional

BList

Cint

DDict

Attempts:

3 left

💡 Hint

Common Mistakes

Not importing Optional when using it.

Using Dict instead of List for categories.

Not assigning a default value to limit.

Use Optional to allow categories to be None or a list of strings. The limit parameter is an integer with a default value.

Practice

1. What is the main purpose of using multiple query parameters in a FastAPI endpoint?

easy

A. To accept several inputs from the URL to customize the response

B. To define multiple routes in one function

C. To handle only POST request data

D. To create database models automatically

Solution

1. Step 1: Understand query parameters in FastAPI

   Query parameters allow passing data in the URL after a question mark, like ?name=John.

2. Step 2: Purpose of multiple query parameters

   Using multiple query parameters lets the API accept many inputs to customize what it returns.

3. Final Answer:

   To accept several inputs from the URL to customize the response -> Option A

4. Quick Check:

   Multiple query parameters = multiple inputs [OK]

Hint: Multiple query parameters let you send many inputs in URL [OK]

Common Mistakes:

• Confusing query parameters with request body
• Thinking multiple query parameters define routes
• Assuming query parameters only work with POST

2. Which of the following is the correct way to declare two query parameters name (string) and age (integer) in a FastAPI path operation function?

easy

A. def read_user(name: str = Query(...), age: int = Query(...)):

B. def read_user(name: str, age: int = None):

C. def read_user(name: int, age: str):

D. def read_user(name, age):

Solution

1. Step 1: Understand FastAPI query parameter declaration

   Using Query(...) marks parameters as required query parameters with type hints.

2. Step 2: Check parameter types and usage

   Parameters must have correct types and use Query(...) to be recognized as query parameters.

3. Final Answer:

   def read_user(name: str = Query(...), age: int = Query(...)): -> Option A

4. Quick Check:

   Use Query(...) with correct types for query parameters [OK]

Hint: Use Query(...) with type hints for required query parameters [OK]

Common Mistakes:

• Swapping types of parameters
• Not using Query for required parameters
• Omitting type hints

3. Given this FastAPI endpoint code:

from fastapi import FastAPI, Query
from typing import List

app = FastAPI()

@app.get('/items/')
async def read_items(q: List[str] = Query([])):
    return {"q": q}

What will be the output if the URL is /items/?q=apple&q=banana?

medium

A. {"q": ["apple"]}

B. {"q": "apple,banana"}

C. {"q": ["apple", "banana"]}

D. {"q": []}

Solution

1. Step 1: Understand List query parameters in FastAPI

   Using List[str] with Query([]) allows multiple values for the same query key to be collected into a list.

2. Step 2: Analyze the URL query parameters

   The URL has q=apple and q=banana, so FastAPI collects both into a list.

3. Final Answer:

   {"q": ["apple", "banana"]} -> Option C

4. Quick Check:

   Multiple query keys = list of values [OK]

Hint: Multiple same keys in URL become list in FastAPI [OK]

Common Mistakes:

• Expecting a single string with commas
• Getting only the first value
• Getting an empty list

4. What is wrong with this FastAPI endpoint code that tries to accept two query parameters name and age?:

from fastapi import FastAPI
app = FastAPI()

@app.get('/user/')
def get_user(name: str, age: int = None):
    return {"name": name, "age": age}

medium

A. The route path should not end with a slash

B. The function must be async

C. Missing Query() for both parameters

D. The parameter age should use Optional[int] for optional query

Solution

1. Step 1: Check optional query parameter typing

   In FastAPI, optional parameters should use Optional[type] or type | None to mark them optional properly.

2. Step 2: Analyze age: int = None

   Just setting default to None is not enough; the type hint should be Optional[int] or int | None for FastAPI to treat it as optional.

3. Final Answer:

   The parameter age should use Optional[int] for optional query -> Option D

4. Quick Check:

   Optional query params need Optional[type] or type | None [OK]

Hint: Use Optional[int] or int | None for optional query params [OK]

Common Mistakes:

• Assuming default None alone makes param optional
• Forgetting to import Optional
• Thinking async is required for all endpoints

5. You want to create a FastAPI endpoint that accepts multiple optional query parameters: tags (list of strings), limit (integer, default 10), and search (optional string). Which of the following function signatures correctly implements this?

hard

A. def get_items(tags: List[str] = Query([]), limit: int = 10, search: str = None):

B. def get_items(tags: List[str] = Query([]), limit: int = Query(10), search: Optional[str] = Query(None)):

C. def get_items(tags: List[str] = [], limit: int = 10, search: str = ''):

D. def get_items(tags: List[str], limit: int = Query(10), search: Optional[str] = Query(None)):

Solution

1. Step 1: Use Query() for query parameters with defaults

   FastAPI requires using Query() to specify default values and metadata for query parameters.

2. Step 2: Correctly type optional parameters

   Use Optional[str] or str | None with Query(None) for optional string parameters.

3. Step 3: Check all parameters in def get_items(tags: List[str] = Query([]), limit: int = Query(10), search: Optional[str] = Query(None)):

   def get_items(tags: List[str] = Query([]), limit: int = Query(10), search: Optional[str] = Query(None)): uses Query([]) for list default, Query(10) for limit default, and Optional[str] = Query(None) for optional search, which is correct.

4. Final Answer:

   def get_items(tags: List[str] = Query([]), limit: int = Query(10), search: Optional[str] = Query(None)): -> Option B

5. Quick Check:

   Use Query() with correct types and defaults for multiple optional queries [OK]

Hint: Use Query() with defaults and Optional for optional query params [OK]

Common Mistakes:

• Using mutable default [] without Query()
• Not marking optional string with Optional
• Omitting Query() for default values