Hi Ben, Is there any real-world scenario where you would need this? It looks like this can help with debugging, somehow, but the easiest solution is to put a "if debug: log(...)" before "yield" in your "switch()" function. You'll have a perfect traceback there. Thanks, Yury On 2015-05-29 12:46 AM, Ben Leslie wrote:
Hi all,
Apologies in advance; I'm not a regular, and this may have been handled already (but I couldn't find it when searching).
I've been using the new async/await functionality (congrats again to Yury on getting that through!), and I'd like to get a stack trace between the place at which blocking occurs and the outer co-routine.
For example, consider this code:
""" async def a(): await b()
async def b(): await switch()
@types.coroutine def switch(): yield
coro_a = a() coro_a.send(None) """
At this point I'd really like to be able to somehow get a stack trace similar to:
test.py:2 test.py:4 test.py:9
Using the gi_frame attribute of coro_a, I can get the line number of the outer frame (e.g.: line 2), but from there there is no way to descend the stack to reach the actual yield point.
I thought that perhaps the switch() co-routine could yield the frame object returned from inspect.currentframe(), however once that function yields that frame object has f_back changed to None.
A hypothetical approach would be to work the way down form the outer-frame, but that requires getting access to the co-routine object that the outer-frame is currently await-ing. Some hypothetical code could be:
""" def show(coro): print("{}:{}".format(coro.gi_frame.f_code.co_filename, coro.gi_frame.f_lineno)) if dis.opname[coro.gi_code.co_code[coro.gi_frame.f_lasti + 1]] == 'YIELD_FROM': show(coro.gi_frame.f_stack[0]) """
This relies on the fact that an await-ing co-routine will be executing a YIELD_FROM instruction. The above code uses a completely hypothetical 'f_stack' property of frame objects to pull the co-routine object which a co-routine is currently await-ing from the stack. I've implemented a proof-of-concept f_stack property in the frameobject.c just to test out the above code, and it seems to work.
With all that, some questions:
1) Does anyone else see value in trying to get the stack-trace down to the actual yield point? 2) Is there a different way of doing it that doesn't require changes to Python internals? 3) Assuming no to #2 is there a better way of getting the information compared to the pretty hacking byte-code/stack inspection?
Thanks,
Ben _______________________________________________ Python-Dev mailing list Python-Dev@python.org https://mail.python.org/mailman/listinfo/python-dev Unsubscribe: https://mail.python.org/mailman/options/python-dev/yselivanov.ml%40gmail.com