How does the EventLoop work in Python? How does asynchrony differ from multithreading and multiprocessing?

In Python, EventLoop is an event processing loop that manages the execution of asynchronous tasks. It monitors the readiness of input/output operations and triggers the corresponding callback functions or coroutines when operations complete.

Asynchrony in Python (for example, using asyncio) allows running multiple tasks without blocking the main thread, using a single thread and switching between tasks while waiting for input/output.

Differences from multithreading and multiprocessing:

• Asynchrony — a single-threaded, non-blocking approach. Tasks switch during waiting times (e.g., reading from a network), saving resources and reducing context switch overhead.

• Multithreading — multiple threads within a single process that can run in parallel, but in Python, due to the GIL (Global Interpreter Lock), true parallelism is limited, especially for CPU-bound tasks.

• Multiprocessing — multiple processes, each with its own memory, which can bypass the GIL and run tasks in parallel on multiple cores, but with higher communication overhead.

Example of a simple EventLoop with asyncio:

import asyncio

async def say_hello():
    await asyncio.sleep(1)
    print("Hello")

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

asyncio.run(main())

Here, two coroutines run asynchronously in a single thread, switching during sleep waiting.