What is the difference between asynchronous programming and using multiple threads in an application?

Asynchronous programming and multithreading are different approaches to executing tasks in parallel.

• Asynchronous programming is based on non-blocking input/output and the use of an event loop. Tasks do not create new threads; instead, when waiting for an operation (such as reading a file or a network request), control returns to the event loop, allowing other tasks to run. This is efficient for a large number of input/output operations.

• Multithreading involves creating multiple execution threads that can run simultaneously (depending on the system and GIL in Python). It is suitable for tasks requiring parallel computations, but in Python, due to the GIL, multithreading is limited for CPU-bound tasks.

Example of asynchronous code in Python using asyncio:

import asyncio

async def fetch_data():
    print('Start fetching')
    await asyncio.sleep(1)  # simulate input/output operation
    print('Done fetching')

async def main():
    await asyncio.gather(fetch_data(), fetch_data())

asyncio.run(main())

Here, two tasks are executed 'in parallel' without creating new threads.