Python asyncio debugging example

Question

I would like to enable Asyncio's un-yielded coroutine detection, but have not succeeded.

This simple code implements the recommendations on:
https://docs.python.org/3/library/asyncio-dev.html#asyncio-logger

but does not actually catch the un-yielded 'dummy' coroutine.

import sys, os
import asyncio
import logging
import warnings

os.environ['PYTHONASYNCIODEBUG'] = '1'
logging.basicConfig(level=logging.DEBUG)
warnings.resetwarnings()

@asyncio.coroutine
def dummy():
    print('yeah, dummy ran!!')

@asyncio.coroutine
def startdummy():
    print('creating dummy')
    dummy()

if __name__ == '__main__':
    lp = asyncio.get_event_loop()
    lp.run_until_complete(startdummy())

I expected that the program would end with a warning about the coroutine 'dummy', created but not yielded from.

Actually, results are:

DEBUG:asyncio:Using selector: SelectSelector
creating dummy
sys:1: ResourceWarning: unclosed <socket object at 0x02DCB6F0>
c:\python34\lib\importlib\_bootstrap.py:2150: ImportWarning: sys.meta_path is empty
sys:1: ResourceWarning: unclosed <socket object at 0x02DE10C0>

No hint of an abandoned coroutine. What am I missing?

Andrew Svetlov · Accepted Answer · 2017-12-21 18:32:14Z

33

asyncio performs check for PYTHONASYNCIODEBUG on module importing.

Thus you need setup environment variable before very first asyncio import:

import os
os.environ['PYTHONASYNCIODEBUG'] = '1'
import asyncio

# rest of your file

edited Dec 21, 2017 at 18:32

answered May 2, 2015 at 9:08

Andrew Svetlov

17.5k8 gold badges70 silver badges72 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

djh Over a year ago

s/import sys/import os/

gelonida Over a year ago

Is this really true? I found some old project with a comment, that os.environ['PYTHONASYNCIODEBUG'] has to be set before the first call to asyncio.get_event_loop() but not before the first import of asyncio I also don't know (the debug feature for this code hasn't been used tested for quite some time) for which versions of asyncio this code was supposed to run.

Andrew Svetlov Over a year ago

Now, in 2019, I recommend you to use async/await syntax. It raises a warning regardless of PYTHONASYNCIODEBUG environment variable value.

Collectives™ on Stack Overflow

Python asyncio debugging example

1 Answer 1

3 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

3 Comments

Your Answer

Sign up or log in

Post as a guest

Related