[issue40438] Python 3.9 eval on list comprehension sometimes returns coroutines
Jonathan Crall added the comment:
This can be closed, but for completeness, the test you ran didn't verify that
the bug was fixed. This is because the hard coded compile flags I gave in my
example seem to have changed in Python 3.9 (is this documented?).
In python3.8 the compile flags I specified correspond to division,
print_function, unicode_literals, and absolute_import.
python3.8 -c "import __future__; print(__future__.print_function.compiler_flag
| __future__.division.compiler_flag | __future__.unicode_literals.compiler_flag
| __future__.absolute_import.compiler_flag)"
Results in: 221184
In Python 3.9 the same code results in: 3538944
I can modify the MWE to accommodate these changes:
./python -c "import __future__; print(eval(compile('[i for i in range(3)]',
mode='eval', filename='fo', flags=__future__.print_function.compiler_flag |
__future__.division.compiler_flag | __future__.unicode_literals.compiler_flag |
__future__.absolute_import.compiler_flag)))"
Which does produce the correct output as expected. So, the issue can remain
closed. I am curious what the bug in 3.9.0a5 was though if you have any
speculations.
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[issue40438] Python 3.9 eval on list comprehension sometimes returns coroutines
Jonathan Crall added the comment:
Ah, sorry. I neglected all the important information.
I tested this using:
Python 3.9.0a5 (default, Apr 23 2020, 14:11:34)
[GCC 8.3.0]
Specifically, I ran in a docker container:
DOCKER_IMAGE=circleci/python:3.9-rc
docker pull $DOCKER_IMAGE
docker run --rm -it $DOCKER_IMAGE bash
And then in the bash shell in the docker image I ran:
python -c "print(eval(compile('[i for i in range(3)]', mode='eval',
filename='foo', flags=221184)))"
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[issue40438] Python 3.9 eval on list comprehension sometimes returns coroutines
New submission from Jonathan Crall :
I first noticed this when testing xdoctest on Python 3.9, and then again when
using IPython.
I was finally able to generate a minimal working example in Python itself. The
following code:
python -c "print(eval(compile('[i for i in range(3)]', mode='eval',
filename='foo', flags=221184)))"
produces
[0, 1, 2]
in Python <= 3.8, but in 3.9 it produces:
at 0x7fa336d40ec0>
:1: RuntimeWarning: coroutine '' was never awaited
RuntimeWarning: Enable tracemalloc to get the object allocation traceback
Is this an intended change? I can't find any notes in the CHANGELOG that seem
to correspond to it.
--
components: Interpreter Core
messages: 367651
nosy: Jonathan Crall
priority: normal
severity: normal
status: open
title: Python 3.9 eval on list comprehension sometimes returns coroutines
versions: Python 3.9
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