New submission from guilimo:
Hello!
I experienced a strange behavior when using a generator, with some code
encapsulated in a try/finally clause or a context manager.
If the generator is not exhausted when we leave the script (because normal end
of script, uncatched exception, etc...), I expect an internal mechanism to
execute properly the finally clause (or __exit__ if context manager).
However, in some specific cases, it seems that this mechanism does not work as
expected.
Example
=======
Consider the following code:
import time
def create_generator():
try:
yield
finally:
time.sleep(2)
ct = create_generator()
ct.next()
If you try to execute it, you will get a:
"Exception AttributeError: "'NoneType' object has no attribute 'sleep'" in
<generator object create_generator at 0x7f04ad62c0f0> ignored"
Description
===========
My understanding is the following (but I may be wrong):
At the end of the script, the garbage collector automatically calls the close()
method of the generator. As a result, GeneratorExit is raised from the "yield",
the finally clause is executed, but for some reason, time does not exist
anymore (already collected by the GC?).
If you try just a print "xxx" instead of the time.sleep, it seems that there is
not any problem.
Important note:
===============
An other very strange thing:
It seems that if I use an other name than "ct" for the generator, the same
exact code runs flawlessly...
You can find attached 3 examples (with try/finally, with a context manager, and
with an other name for the generator).
I also found this ticket where some discussion may be related to my situation,
even if not describing exactly my current problem:
https://bugs.python.org/issue25014
----------
components: Interpreter Core
files: examples.zip
messages: 250460
nosy: guilimo
priority: normal
severity: normal
status: open
title: Clean issue when generator not exhausted (garbage collector related?)
type: crash
versions: Python 2.7
Added file: http://bugs.python.org/file40436/examples.zip
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Python tracker <[email protected]>
<http://bugs.python.org/issue25069>
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