Async HTTP client calls in FastAPI - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to import the async HTTP client from httpx.

FastAPI

from [1] import AsyncClient

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

Aasyncio

Brequests

Cfastapi

Dhttpx

Attempts:

3 left

💡 Hint

Common Mistakes

Importing AsyncClient from requests instead of httpx.

Trying to import AsyncClient from fastapi.

The AsyncClient class is imported from the httpx library to make async HTTP calls.

2fill in blank

medium

Complete the code to create an async function that makes a GET request using AsyncClient.

FastAPI

async def fetch_data(url: str):
    async with AsyncClient() as client:
        response = await client.[1](url)
        return response.text

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

Apost

Bput

Cget

Ddelete

Attempts:

3 left

💡 Hint

Common Mistakes

Using post instead of get for fetching data.

Forgetting to await the async call.

To retrieve data, the get method is used on the async client.

3fill in blank

hard

Fix the error in the async function to correctly return JSON data from the response.

FastAPI

async def fetch_json(url: str):
    async with AsyncClient() as client:
        response = await client.get(url)
        data = await response.[1]()
        return data

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

Atext

Bjson

Ccontent

Dread

Attempts:

3 left

💡 Hint

Common Mistakes

Using response.text() which returns a string, not parsed JSON.

Using response.content() which returns bytes.

The json() method asynchronously parses the response body as JSON.

4fill in blank

hard

Fill both blanks to create a FastAPI route that calls the async fetch_data function and returns the result.

FastAPI

from fastapi import FastAPI

app = FastAPI()

@app.[1]("/data")
async def get_data():
    result = await fetch_data([2])
    return {"data": result}

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

Aget

B"https://example.com/api"

C"/fetch"

Dpost

Attempts:

3 left

💡 Hint

Common Mistakes

Using @app.post instead of @app.get for a GET route.

Passing a variable name instead of a URL string to fetch_data.

The route uses the @app.get decorator for GET requests and calls fetch_data with the URL string.

5fill in blank

hard

Fill all three blanks to create an async function that posts JSON data and returns the JSON response.

FastAPI

async def post_json(url: str, payload: dict):
    async with AsyncClient() as client:
        response = await client.[1](url, json=[2])
        return await response.[3]()

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

Apost

Bpayload

Cjson

Dtext

Attempts:

3 left

💡 Hint

Common Mistakes

Using get instead of post for sending data.

Passing payload as a positional argument instead of json keyword.

Using response.text() instead of response.json() to parse JSON.

The post method sends JSON data using the json parameter, and the response is parsed as JSON.

Practice

1. What is the main benefit of using async HTTP client calls in a FastAPI application?

easy

A. They allow the app to handle other tasks while waiting for the HTTP response.

B. They make the HTTP response faster from the server side.

C. They automatically cache all HTTP responses.

D. They convert HTTP calls into database queries.

Solution

1. Step 1: Understand async behavior in FastAPI

   Async calls let the app continue working without waiting for the HTTP response, improving responsiveness.

2. Step 2: Identify the benefit of async HTTP client calls

   This means the app can handle other requests or tasks while waiting, making it efficient.

3. Final Answer:

   They allow the app to handle other tasks while waiting for the HTTP response. -> Option A

4. Quick Check:

   Async calls improve responsiveness = B [OK]

Hint: Async means non-blocking wait for HTTP response [OK]

Common Mistakes:

• Thinking async makes server response faster
• Confusing async with caching
• Believing async converts HTTP to database calls

2. Which of the following is the correct way to create an async HTTP client call using httpx in FastAPI?

easy

A. async with httpx.AsyncClient() as client: response = await client.get('https://example.com')

B. response = httpx.get('https://example.com')

C. client = httpx.Client(); response = client.get('https://example.com')

D. client = httpx.AsyncClient(); response = client.get('https://example.com')

Solution

1. Step 1: Identify async client usage

   Using async with ensures proper resource management for async clients.

2. Step 2: Use await to wait for the async HTTP call

   The call to client.get() must be awaited to get the response asynchronously.

3. Final Answer:

   async with httpx.AsyncClient() as client: response = await client.get('https://example.com') -> Option A

4. Quick Check:

   Use async with and await for async calls = C [OK]

Hint: Use async with and await for async HTTP calls [OK]

Common Mistakes:

• Using httpx.Client instead of AsyncClient for async calls
• Not using await with async client.get()
• Not using async with for client context

3. What will be the output of this FastAPI async function when called?

import httpx
from fastapi import FastAPI
app = FastAPI()

@app.get('/data')
async def get_data():
    async with httpx.AsyncClient() as client:
        response = await client.get('https://httpbin.org/get')
    return {'status_code': response.status_code}

medium

A. SyntaxError in async function

B. {'status_code': '200'}

C. RuntimeError due to missing await

D. {'status_code': 200}

Solution

1. Step 1: Analyze the async HTTP call

   The function uses await with client.get(), so it correctly waits for the response.

2. Step 2: Check the returned data

   The response status code is an integer 200 for a successful HTTP GET, returned inside a dictionary.

3. Final Answer:

   {'status_code': 200} -> Option D

4. Quick Check:

   Awaited async call returns status 200 = A [OK]

Hint: Await async calls to get response object correctly [OK]

Common Mistakes:

• Returning status code as string instead of int
• Forgetting await causing runtime errors
• Syntax errors from incorrect async usage

4. Identify the error in this FastAPI async HTTP client code:

import httpx
from fastapi import FastAPI
app = FastAPI()

@app.get('/info')
async def get_info():
    client = httpx.AsyncClient()
    response = client.get('https://httpbin.org/get')
    return {'status': response.status_code}

medium

A. Using httpx.Client instead of AsyncClient

B. Missing await before client.get() call

C. Missing async keyword in function definition

D. Incorrect return type, should return string

Solution

1. Step 1: Check async call usage

   The client.get() is an async method and must be awaited to get the response.

2. Step 2: Identify missing await

   Without await, the code returns a coroutine object, causing errors when accessing status_code.

3. Final Answer:

   Missing await before client.get() call -> Option B

4. Quick Check:

   Async calls require await = A [OK]

Hint: Always await async client.get() calls [OK]

Common Mistakes:

• Not awaiting async HTTP calls
• Using sync client in async function
• Forgetting async keyword on function

5. You want to fetch data from two different URLs concurrently in a FastAPI async endpoint. Which code correctly achieves this using httpx.AsyncClient?

hard

A. async with httpx.AsyncClient() as client:
r1 = await client.get(url1)
r2 = await client.get(url2)
return {'r1': r1.status_code, 'r2': r2.status_code}

B. async with httpx.AsyncClient() as client:
r1, r2 = await client.get(url1), await client.get(url2)
return {'r1': r1.status_code, 'r2': r2.status_code}

C. async with httpx.AsyncClient() as client:
import asyncio
r1, r2 = await asyncio.gather(client.get(url1), client.get(url2))
return {'r1': r1.status_code, 'r2': r2.status_code}

D. client = httpx.AsyncClient()
r1 = client.get(url1)
r2 = client.get(url2)
return {'r1': r1.status_code, 'r2': r2.status_code}

Solution

1. Step 1: Understand concurrency with async HTTP calls

   To run multiple async calls concurrently, use asyncio.gather() to await them together.

2. Step 2: Check code correctness

   async with httpx.AsyncClient() as client: import asyncio r1, r2 = await asyncio.gather(client.get(url1), client.get(url2)) return {'r1': r1.status_code, 'r2': r2.status_code} uses asyncio.gather() inside async with context, correctly awaiting both calls concurrently.

3. Final Answer:

   async with httpx.AsyncClient() as client: import asyncio r1, r2 = await asyncio.gather(client.get(url1), client.get(url2)) return {'r1': r1.status_code, 'r2': r2.status_code} -> Option C

4. Quick Check:

   Use asyncio.gather for concurrent async calls = D [OK]

Hint: Use asyncio.gather to await multiple async calls concurrently [OK]

Common Mistakes:

• Awaiting calls sequentially losing concurrency
• Not awaiting calls causing coroutine errors
• Not using async with for client context