Mailman 3 February 2020 - docs

[issue39375] Document os.environ[x] = y and os.putenv() as thread unsafe
by Gregory P. Smith 05 Mar '21

05 Mar '21

New submission from Gregory P. Smith <greg(a)krypto.org>: The underlying API calls made by os.putenv() and os.environ[name] = value syntax are not thread safe on POSIX systems. POSIX _does not have_ any thread safe way to access the process global environment. In a pure Python program, the GIL prevents this from being an issue. But when embedded in a C/C++ program or using extension modules that launch their own threads from C, those threads could also make the invalid assumption that they can safely _read_ the environment. Which is a race condition when a Python thread is doing a putenv() at the same time. We should document the danger. CPython's os module snapshots a copy of the environment into a dict at import time (during CPython startup). But os.environ[] assignment and os.putenv() modify the actual process global environment in addition to updating this dict. (If an embedded interpreter is launched from a process with other threads already running, even that initial environment reading could be unsafe if the larger application has a thread that wrongly assumes it has exclusive environment access) For people modifying os.environ so that the change is visible to child processes, we can recommend using the env= parameter on subprocess API calls to supply a new environment. A broader issue of should we be modifying the process global environment state at all from os.putenv() and os.environ[] assignment still exists. I'll track that in another issue (to be opened). ---------- assignee: docs@python components: Documentation messages: 360221 nosy: docs@python, gregory.p.smith priority: normal severity: normal status: open title: Document os.environ[x] = y and os.putenv() as thread unsafe versions: Python 2.7, Python 3.7, Python 3.8, Python 3.9 _______________________________________ Python tracker <report(a)bugs.python.org> <https://bugs.python.org/issue39375> _______________________________________

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[issue29829] Documentation lacks clear warning of subprocess issue with pythonw
by Steve Barnes 05 Mar '21

05 Mar '21

New submission from Steve Barnes: When running under pythonw, or pyinstaller with the -w flag, modules that use subprocess calls such as popen, run, etc. will crash if the default `stdout=None, stderr=None` behaviour is used rather than PIPE. This is an obscure problem which is very hard to debug yet there is no warning in the documentation on this. I would like to suggest adding a :warning:`stdout=None, stderr=None` must not be used in any of the calls in this module when running under pythonw due to the lack of sys.stdout & sys.stderr in that case. Please use `stdout=PIPE, stderr=PIPE` instead. A patch against the default branch would be: diff -r 4243df51fe43 Doc/library/subprocess.rst --- a/Doc/library/subprocess.rst Fri Feb 10 14:19:36 2017 +0100 +++ b/Doc/library/subprocess.rst Thu Mar 16 16:56:24 2017 +0000 @@ -33,6 +33,13 @@ function for all use cases it can handle. For more advanced use cases, the underlying :class:`Popen` interface can be used directly. +.. warning:: Do not use default parameters on Windows with pythonw. + + As pythonw deletes `sys.stdout` & `sys.stderr` the use of the default + parameters, `stdout=None, stderr=None,`, which defaults to being + `stdout=sys.stdout, stderr=sys.stderr,` may cause unexpected crashes + it is recommended to use `stdout=PIPE, stderr=PIPE,` instead. + The :func:`run` function was added in Python 3.5; if you need to retain compatibility with older versions, see the :ref:`call-function-trio` section. ---------- assignee: docs@python components: Documentation messages: 289722 nosy: Steve Barnes, docs@python priority: normal severity: normal status: open title: Documentation lacks clear warning of subprocess issue with pythonw type: behavior versions: Python 2.7, Python 3.6, Python 3.7 _______________________________________ Python tracker <report(a)bugs.python.org> <http://bugs.python.org/issue29829> _______________________________________

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[issue12594] Docs for py3k still refer to "MacPython 2.5 folder"
by Christoph Schindler 04 Mar '21

04 Mar '21

New submission from Christoph Schindler <hop(a)30hopsmax.at>: In http://docs.python.org/py3k/using/mac.html#getting-and-installing-macpython and http://docs.python.org/py3k/using/mac.html#distributing-python-applications… . ---------- assignee: docs@python components: Documentation messages: 140744 nosy: docs@python, hop priority: normal severity: normal status: open title: Docs for py3k still refer to "MacPython 2.5 folder" versions: Python 3.1, Python 3.2 _______________________________________ Python tracker <report(a)bugs.python.org> <http://bugs.python.org/issue12594> _______________________________________

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[issue39199] Improve the AST documentation
by Pablo Galindo Salgado 04 Mar '21

04 Mar '21

New submission from Pablo Galindo Salgado <pablogsal(a)gmail.com>: The AST docs need some love as they can be a bit obscure to someone new to the module. Improvements to be considered in this issue: * Document all available nodes (as of 3.8 and not deprecated ones). This helps to know what classes to consider when implementing methods for the visitors. * Add some short practical examples for the visitors: one to query an AST and another to modify it. ---------- assignee: docs@python components: Documentation messages: 359235 nosy: docs@python, pablogsal priority: normal severity: normal status: open title: Improve the AST documentation versions: Python 3.9 _______________________________________ Python tracker <report(a)bugs.python.org> <https://bugs.python.org/issue39199> _______________________________________

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[issue24650] Error in yield expression documentation
by swanson 28 Feb '21

28 Feb '21

New submission from swanson: https://docs.python.org/3/reference/expressions.html in 6.2.9. Yield expressions end of 1st paragraph: "Using a yield expression in a function’s body causes that function to be a generator." NO! As the very next sentence explains, a generator is what's returned by such a function, not the function itself. Basically, it should be sufficient to add the word "function" to the end of that sentence: "... generator function." However, this error does NOT exist in 3.0 to 3.2 - just in 3.3 to 3.6, so I suggest just using the same wording as 3.0 to 3.2: "Using a yield expression in a function definition is sufficient to cause that definition to create a generator function instead of a normal function." ---------- assignee: docs@python components: Documentation messages: 246841 nosy: docs@python, swanson priority: normal severity: normal status: open title: Error in yield expression documentation versions: Python 3.3, Python 3.4, Python 3.5, Python 3.6 _______________________________________ Python tracker <report(a)bugs.python.org> <http://bugs.python.org/issue24650> _______________________________________

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[issue29045] Outdated C api doc about Windows error
by Xiang Zhang 27 Feb '21

27 Feb '21

New submission from Xiang Zhang: https://docs.python.org/3.7/c-api/exceptions.html#c.PyErr_SetFromWindowsErr… it stills refers to PyErr_SetFromWindowsErrWithFilenameObject but this function doesn't exist since Py3.4. I didn't find when and why it's deleted. And https://docs.python.org/3.4/c-api/exceptions.html#c.PyErr_SetFromWindowsErr raises OSError instead of WindowsError. ---------- assignee: docs@python components: Documentation messages: 283814 nosy: docs@python, xiang.zhang priority: normal severity: normal status: open title: Outdated C api doc about Windows error versions: Python 3.5, Python 3.6, Python 3.7 _______________________________________ Python tracker <report(a)bugs.python.org> <http://bugs.python.org/issue29045> _______________________________________

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[issue24045] Behavior of large returncodes (sys.exit(nn))
by Ethan Furman 27 Feb '21

27 Feb '21

New submission from Ethan Furman: Not sure if this is a bug, or just One of Those Things: sys.exit(large_value) can wrap around if the value is too large, but this is O/S dependent. linux (ubuntu 14.04) $ python Python 2.7.8 (default, Oct 20 2014, 15:05:29) [GCC 4.9.1] on linux2 Type "help", "copyright", "credits" or "license" for more information. --> import sys --> sys.exit(256) $ echo $? 0 $ python Python 2.7.8 (default, Oct 20 2014, 15:05:29) [GCC 4.9.1] on linux2 Type "help", "copyright", "credits" or "license" for more information. --> import sys --> sys.exit(257) $ echo $? 1 M$ (Windows 7) > python Python 2.7... --> import sys --> sys.exit(65535) > echo %errorlevel% 65535 > python Python 2.7... --> import sys --> sys.exit(100000) > echo %errorlevel% 100000 Perhaps a minor doc update that talks about return codes and why they might not be exactly what was given to Python? ---------- assignee: docs@python messages: 241903 nosy: docs@python, ethan.furman priority: normal severity: normal status: open title: Behavior of large returncodes (sys.exit(nn)) versions: Python 2.7, Python 3.5 _______________________________________ Python tracker <report(a)bugs.python.org> <http://bugs.python.org/issue24045> _______________________________________

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[issue13368] Possible problem in documentation of module subprocess, method send_signal
by Eli Bendersky 25 Feb '21

25 Feb '21

New submission from Eli Bendersky <eliben(a)gmail.com>: docs@ list report by Daniel Dieterle: in the documentation (http://docs.python.org/library/subprocess.html#subprocess.Popen.send_signal) is a bug. CTRL_C_EVENT can not be sent to processes started with a creationflags parameter which includes CREATE_NEW_PROCESS_GROUP. Why can be read in the msdn documentation http://msdn.microsoft.com/en-us/library/windows/desktop/ms683155%28v=vs.85%… . A workaround using CTRL_C_EVENT nevertheless is described here: http://stackoverflow.com/questions/7085604/sending-c-to-python-subprocess-o… -- I do not know why the subprocess.CREATE_NEW_PROCESS_GROUP parameter was introduced. But it is useless for terminating a process with os.kill() in combination with signal.SIGTERM, which corresponds to a CTRL-C-EVENT. A CTRL-C-EVENT is only forwarded to the process if the process group is zero. Therefore the Note in the documentation on Popen.send_signal() is wrong. ---------- assignee: docs@python components: Documentation messages: 147272 nosy: docs@python, eli.bendersky priority: normal severity: normal status: open title: Possible problem in documentation of module subprocess, method send_signal versions: Python 2.7 _______________________________________ Python tracker <report(a)bugs.python.org> <http://bugs.python.org/issue13368> _______________________________________

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[issue16954] Add docstrings for ElementTree module
by Serhiy Storchaka 22 Feb '21

22 Feb '21

New submission from Serhiy Storchaka: Perhaps almost all Doxygen comments in ElementTree module should be converted to docstrings. ---------- assignee: docs@python components: Documentation, XML messages: 179881 nosy: docs@python, eli.bendersky, serhiy.storchaka priority: normal severity: normal stage: needs patch status: open title: Add docstrings for ElementTree module type: enhancement versions: Python 3.4 _______________________________________ Python tracker <report(a)bugs.python.org> <http://bugs.python.org/issue16954> _______________________________________

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[issue27646] yield from expression can be any iterable
by Terry J. Reedy 21 Feb '21

21 Feb '21

New submission from Terry J. Reedy: https://docs.python.org/3/reference/expressions.html#yield-expressions says "When yield from <expr> is used, it treats the supplied expression as a subiterator. All values produced by that subiterator ...". To me "treats..expression as a subiterator" means that the expression must *be* an iterator, such as returned by iter or calling a generator function. Hence I was surprised upon reading "yield from <non-iterator iterable>" in stdlib code. I confirmed that this usage is correct by trying >>> def g(): yield from (1,2) >>> i = g() >>> next(i), next(i) (1, 2) and then reading the PEP380 Formal Semantics, which begins with "_i = iter(EXPR)". Hence I suggest the following replacement for the quote above: "When yield from <expr> is used, the expression must be an iterable. A subiterator is obtained with iter(<expr>). All values produced by that subiterator ...". Note that 'subiterator' is spelled in the following sentences 'underlying iterable' (which I am not sure I like) and 'sub-iterator' (and 'sub-generator'). I think we should be consistent for at least the two short 'yield from' paragraphs. ---------- assignee: docs@python components: Documentation messages: 271577 nosy: docs@python, terry.reedy priority: normal severity: normal stage: patch review status: open title: yield from expression can be any iterable type: behavior versions: Python 3.5, Python 3.6 _______________________________________ Python tracker <report(a)bugs.python.org> <http://bugs.python.org/issue27646> _______________________________________

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