What are some examples of using asyncio in Python?

What are some examples of using asyncio in Python?

Asyncio is a library in Python used for writing concurrent code using the async/await syntax. Here are a few examples:

1. Basic Async Function: You can define an async function using the async def syntax and call it with await.

2. Running Multiple Coroutines: Use asyncio.gather() to run multiple coroutines concurrently.

3. Async HTTP Requests: Libraries like aiohttp allow you to make asynchronous HTTP requests.

Would you like to see a specific example of any of these?

Yes, can you show me an example of running multiple coroutines?

Sure! Here's a simple example:

import asyncio

async def fetch_data(num):
    print(f'Starting fetch {num}')
    await asyncio.sleep(2)  # Simulate a network delay
    print(f'Finished fetch {num}')
    return f'Data {num}'

async def main():
    tasks = [fetch_data(i) for i in range(5)]
    results = await asyncio.gather(*tasks)
    print(results)

asyncio.run(main())

This code will run five fetch operations concurrently. Each fetch simulates a delay of 2 seconds.

That's great! How does asyncio.gather() work?

asyncio.gather() takes multiple awaitable objects (like coroutines) and runs them concurrently. It waits for all of them to complete and returns their results as a list. If any of the awaitables raise an exception, asyncio.gather() will raise that exception as well. It's a powerful way to manage multiple asynchronous tasks.

Can you give me an example of using aiohttp with asyncio?

Absolutely! Here's a basic example of using aiohttp to make asynchronous HTTP requests:

import aiohttp
import asyncio

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

async def main():
    urls = ['http://example.com', 'http://example.org']
    tasks = [fetch(url) for url in urls]
    results = await asyncio.gather(*tasks)
    print(results)

asyncio.run(main())

This code fetches the content of two URLs concurrently.