Fetching data asynchronously from multiple URLs using Python async IO

Python Asynchronous: Exercise-4 with Solution

Write a Python program that implements a coroutine to fetch data from two different URLs simultaneously using the "aiohttp" library.

Sample Solution:

Code:

import asyncio
import aiohttp
async def fetch_url(url):
    async with aiohttp.ClientSession() as session:
        async with session.get(url) as response:
            return await response.text()
async def main():
    url_1 = "https://www.wikipedia.org/"
    url_2 = "https://www.google.com"    
    task1 = asyncio.create_task(fetch_url(url_1))
    task2 = asyncio.create_task(fetch_url(url_2))    
    data1 = await task1
    data2 = await task2    
    print("Data from ",url_1, len(data1), "bytes")
    print("Data from ",url_2, len(data2), "bytes")
# Run the event loop
asyncio.run(main())

Output:

Data from  https://www.wikipedia.org/ 74154 bytes
Data from  https://www.google.com 18273 bytes

Explanation:

In the above exercise-

• The "fetch_url()" function coroutine is defined to asynchronously fetch data from a given URL using the 'aiohttp' library. It uses an aiohttp.ClientSession() to manage the HTTP requests and responses. The 'async' with syntax ensures that the session is properly closed.
• The main coroutine is defined to run asynchronous operations. It creates two tasks using asyncio.create_task() that execute the fetch_url coroutine concurrently for two different URLs.
• The 'await' keyword is used to wait for the completion of each task, storing the fetched data in data1 and data2.
• Finally, the program prints the size of the fetched data from both URLs.

Flowchart:

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