What are the consequences (if any) of not running asyncio.set_event_loop(event_loop) after event_loop = asyncio.new_event_loop?

Question

What are the consequences (if any) of not running asyncio.set_event_loop(event_loop) after event_loop = asyncio.new_event_loop? And if there are none then what’s the purpose of asyncio.set_event_loop?

I have written some basic test code without set_event_loop to figure out what it does and I saw no change, so now I’m left wondering what the consequences of not using it are / what the purpose of it is.

The documentation says: "Set loop as the current event loop for the current OS thread."

But I’m not sure how that’s useful.

Test code:

import asyncio

async def test1():
    count = 0
    while True:
        count += 1
        await asyncio.sleep(1)
        print(count)

loop = asyncio.new_event_loop()
loop.run_until_complete(test1())

What I’ve learned since

asyncio.get_running_loop is thread specific and you won’t be able to use it without setting the event loop to the current thread. In other words you cant run it without running asyncio.set_event_loop first

Asked By: Avadx FeIRM

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Source

Answer 1

As per your comment. Here is an example of when you might use asyncio.set_event_loop(event_loop):

import asyncio

# Create a new event loop
event_loop = asyncio.new_event_loop()

# Set the event loop as the default event loop for the current thread
asyncio.set_event_loop(event_loop)

# Run an asynchronous task using the event loop
async def my_task():
    print('Hello, world!')

event_loop.run_until_complete(my_task())

# Close the event loop
event_loop.close()

In this example, we create a new event loop using asyncio.new_event_loop(), and then set it as the default event loop for the current thread using asyncio.set_event_loop(event_loop). We can then run an asynchronous task using the event loop with event_loop.run_until_complete(my_task()).

The code in the original question is already the counter example. In fact i tend to use the code in the question more than that code in this answer (because it was the historical conventional method).

You might use asyncio.set_event_loop(event_loop) if you want to create a custom event loop with specific settings or behaviors, or if you want to use a different event loop than the default event loop provided by the asyncio module….

Answered By: D.L

What are the consequences (if any) of not running asyncio.set_event_loop(event_loop) after event_loop = asyncio.new_event_loop?

Question:

What I’ve learned since

Answers: