Code-Memo

Asynchronous Programming

async and await Syntax

• async def: Declares a coroutine function, which can use await to suspend its execution until the result of an asynchronous operation is available.
• await: Suspends the execution of the coroutine until the awaited coroutine or Future completes and returns the result.

import asyncio

async def async_task():
    print("Task started")
    await asyncio.sleep(1)
    print("Task completed")

# Running an asynchronous coroutine
asyncio.run(async_task())

Asynchronous I/O Operations

Asynchronous I/O operations involve tasks that wait for external resources. Asyncio provides mechanisms to handle these operations efficiently without blocking the event loop.

Asynchronous HTTP Request with aiohttp

import aiohttp
import asyncio

async def fetch_data(url):
    async with aiohttp.ClientSession() as session:
        async with session.get(url) as response:
            return await response.text()

async def main():
    url = 'https://jsonplaceholder.typicode.com/posts/1'
    response = await fetch_data(url)
    print(response)

asyncio.run(main())

• aiohttp.ClientSession: Manages HTTP connections and provides a context manager for making HTTP requests asynchronously.
• session.get(url): Initiates an asynchronous GET request to the specified URL.
• response.text(): Asynchronously retrieves and returns the response body as text.

Why do we use Async?

• Non-blocking operations allow other tasks to run while waiting for I/O.
• Handles large numbers of concurrent connections efficiently.
• Avoids callback-based programming with clearer syntax using async and await.