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Subject: asyncio
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Hi,

I wrote simple asyncio program (see below) and I'm not sure if I understand
behavior correctly.
I have print_tasks coroutine which prints each task in a loop by using
Task.all_tasks function.
I have also task_launcher coroutine that launches (by loop.create_task())
simple task that waits some and prints "ping".
Question is why finished "ping" tasks keep accumulating in Task.all_tasks?
After a while there is a lot of:
<Task finished coro=<ping() done, defined at test.py:25> result=None>

when printing in Task.all_tasks and number of those increases as new ping
tasks are launched

Is there a way to prune finished tasks (I tried forcing gc) or I do
something wrong?

I ran on python 3.4.3.

Best regards,
L

import asyncio

loop = asyncio.get_event_loop()

@asyncio.coroutine
def print_tasks(loop):
        while True:
                tasks = asyncio.Task.all_tasks(loop)

                for task in tasks:
                        print(task)
                print()

                yield from asyncio.sleep(1)

@asyncio.coroutine
def task_launcher(loop):
        while True:
                yield from asyncio.sleep(1)
                loop.create_task(ping())

@asyncio.coroutine
def ping():
        yield from asyncio.sleep(2)
        print("ping")


loop.create_task(print_tasks(loop))
loop.create_task(task_launcher(loop))

loop.run_forever()

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Content-Transfer-Encoding: quoted-printable

<div dir=3D"ltr">Hi,<div><br></div><div>I wrote simple asyncio program (see=
 below) and I&#39;m not sure if I understand behavior correctly.</div><div>=
I have print_tasks coroutine which prints each task in a loop by using Task=
.all_tasks function.</div><div>I have also task_launcher coroutine that lau=
nches (by loop.create_task()) simple task that waits some and prints &quot;=
ping&quot;.<br>Question is why finished &quot;ping&quot; tasks keep accumul=
ating in Task.all_tasks? After a while there is a lot of:</div><div><div>&l=
t;Task finished coro=3D&lt;ping() done, defined at test.py:25&gt; result=3D=
None&gt;</div></div><div><br></div><div>when printing in Task.all_tasks and=
 number of those increases as new ping tasks are launched</div><div><br></d=
iv><div>Is there a way to prune finished tasks (I tried forcing gc) or I do=
 something wrong?</div><div><br></div><div>I ran on python 3.4.3.</div><div=
><br></div><div>Best regards,</div><div>L</div><div><br></div><div><div>imp=
ort asyncio</div><div><br></div><div>loop =3D asyncio.get_event_loop()</div=
><div><br></div><div>@asyncio.coroutine</div><div>def print_tasks(loop):</d=
iv><div>=C2=A0 =C2=A0 =C2=A0 =C2=A0 while True:</div><div>=C2=A0 =C2=A0 =C2=
=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 tasks =3D asyncio.Task.all_tasks(loo=
p)</div><div><br></div><div>=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=
=A0 =C2=A0 for task in tasks:</div><div>=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 print(task)</div><div>=C2=
=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 print()</div><div><br>=
</div><div>=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 yield fr=
om asyncio.sleep(1)</div><div><br></div><div>@asyncio.coroutine</div><div>d=
ef task_launcher(loop):</div><div>=C2=A0 =C2=A0 =C2=A0 =C2=A0 while True:</=
div><div>=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 yield from=
 asyncio.sleep(1)</div><div>=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=
=A0 =C2=A0 loop.create_task(ping())</div><div><br></div><div>@asyncio.corou=
tine</div><div>def ping():</div><div>=C2=A0 =C2=A0 =C2=A0 =C2=A0 yield from=
 asyncio.sleep(2)</div><div>=C2=A0 =C2=A0 =C2=A0 =C2=A0 print(&quot;ping&qu=
ot;)</div><div><br></div><div><br></div><div>loop.create_task(print_tasks(l=
oop))</div><div>loop.create_task(task_launcher(loop))</div><div><br></div><=
div>loop.run_forever()</div></div><div><br></div></div>

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