Mailman 3 May 2020 - docs

[issue37205] time.perf_counter() is not system-wide on Windows, in disagreement with documentation
by Ken Healy 21 Mar '21

21 Mar '21

New submission from Ken Healy <healykb+pythonbugs(a)gmail.com>: The documentation for time.perf_counter() indicates it should return a system-wide value: https://docs.python.org/3/library/time.html#time.perf_counter This is not true on Windows, as a process-specific offset is subtracted from the underlying QueryPerformanceCounter() value. The code comments indicate this is to reduce precision loss: https://github.com/python/cpython/blob/master/Python/pytime.c#L995-L997 This is relevant in multiprocess applications, where accurate timing is required across multiple processes. Here is a simple test case: ----------------------------------------------------------- import concurrent.futures import time def worker(): return time.perf_counter() if __name__ == '__main__': pool = concurrent.futures.ProcessPoolExecutor() futures = [] for i in range(3): print('Submitting worker {:d} at time.perf_counter() == {:.3f}'.format(i, time.perf_counter())) futures.append(pool.submit(worker)) time.sleep(1) for i, f in enumerate(futures): print('Worker {:d} started at time.perf_counter() == {:.3f}'.format(i, f.result())) ----------------------------------------------------------- Output: ----------------------------------------------------------- C:\...>Python37\python.exe -VV Python 3.7.3 (v3.7.3:ef4ec6ed12, Mar 25 2019, 22:22:05) [MSC v.1916 64 bit (AMD64)] C:\...>Python37\python.exe perf_counter_across_processes.py Submitting worker 0 at time.perf_counter() == 0.376 Submitting worker 1 at time.perf_counter() == 1.527 Submitting worker 2 at time.perf_counter() == 2.529 Worker 0 started at time.perf_counter() == 0.380 Worker 1 started at time.perf_counter() == 0.956 Worker 2 started at time.perf_counter() == 1.963 ----------------------------------------------------------- See my stackoverflow question for a comparison with Linux: https://stackoverflow.com/questions/56502111/should-time-perf-counter-be-co… ---------- assignee: docs@python components: Documentation, Library (Lib), Windows messages: 345057 nosy: docs@python, kh90909, paul.moore, steve.dower, tim.golden, vstinner, zach.ware priority: normal severity: normal status: open type: behavior versions: Python 3.5, Python 3.6, Python 3.7, Python 3.8, Python 3.9 _______________________________________ Python tracker <report(a)bugs.python.org> <https://bugs.python.org/issue37205> _______________________________________

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[issue37891] Exceptions tutorial page does not mention raise from
by Niels Albers 21 Mar '21

21 Mar '21

New submission from Niels Albers <nralbers(a)gmail.com>: raise <Exception> from <exception instance> has been in the language since python 3, yet the tutorial page teaching about exceptions does not mention it. (see https://docs.python.org/3.7/tutorial/errors.html#raising-exceptions) It would be especially helpful to language newcomers to touch on the possibility of passing error context when raising a new exception in an exception handler. ---------- assignee: docs@python components: Documentation messages: 349994 nosy: Niels Albers, docs@python priority: normal severity: normal status: open title: Exceptions tutorial page does not mention raise from versions: Python 3.5, Python 3.6, Python 3.7, Python 3.8, Python 3.9 _______________________________________ Python tracker <report(a)bugs.python.org> <https://bugs.python.org/issue37891> _______________________________________

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[issue14189] Documentation for some C APIs is missing clear specification of the type of reference they return
by Baruch Sterin 21 Mar '21

21 Mar '21

New submission from Baruch Sterin <python(a)bsterin.com>: In addition to the description text, most C API functions have a one-line, emphasized specification whether they return a new or a borrowed reference. (e.g. 'Return value: New reference.'). The following API functions are missing that. Some of them, like PyMemoryView_FromBuffer(), have descriptions that are clear, but it would still be nice to have an unambiguous statement like most other API functions have. The list has been generated automatically, so it might contain some errors. Doc/c-api/arg.rst: Py_VaBuildValue Doc/c-api/buffer.rst: PyMemoryView_FromBuffer Doc/c-api/buffer.rst: PyMemoryView_FromObject Doc/c-api/buffer.rst: PyMemoryView_GetContiguous Doc/c-api/bytearray.rst: PyByteArray_Concat Doc/c-api/bytearray.rst: PyByteArray_FromObject Doc/c-api/bytearray.rst: PyByteArray_FromStringAndSize Doc/c-api/code.rst: PyCode_New Doc/c-api/codec.rst: PyCodec_BackslashReplaceErrors Doc/c-api/codec.rst: PyCodec_Decode Doc/c-api/codec.rst: PyCodec_Decoder Doc/c-api/codec.rst: PyCodec_Encode Doc/c-api/codec.rst: PyCodec_Encoder Doc/c-api/codec.rst: PyCodec_IgnoreErrors Doc/c-api/codec.rst: PyCodec_IncrementalDecoder Doc/c-api/codec.rst: PyCodec_IncrementalEncoder Doc/c-api/codec.rst: PyCodec_LookupError Doc/c-api/codec.rst: PyCodec_ReplaceErrors Doc/c-api/codec.rst: PyCodec_StreamReader Doc/c-api/codec.rst: PyCodec_StreamWriter Doc/c-api/codec.rst: PyCodec_StrictErrors Doc/c-api/codec.rst: PyCodec_XMLCharRefReplaceErrors Doc/c-api/exceptions.rst: PyUnicodeDecodeError_Create Doc/c-api/exceptions.rst: PyUnicodeDecodeError_GetEncoding Doc/c-api/exceptions.rst: PyUnicodeDecodeError_GetObject Doc/c-api/exceptions.rst: PyUnicodeDecodeError_GetReason Doc/c-api/exceptions.rst: PyUnicodeEncodeError_Create Doc/c-api/exceptions.rst: PyUnicodeTranslateError_Create Doc/c-api/float.rst: PyFloat_GetInfo Doc/c-api/import.rst: PyImport_GetImporter Doc/c-api/import.rst: PyImport_ImportModuleNoBlock Doc/c-api/import.rst: _PyImport_FindExtension Doc/c-api/import.rst: _PyImport_FixupExtension Doc/c-api/init.rst: PyEval_GetCallStats Doc/c-api/int.rst: PyInt_FromSize_t Doc/c-api/long.rst: PyLong_FromSize_t Doc/c-api/long.rst: PyLong_FromSsize_t Doc/c-api/number.rst: PyNumber_Index Doc/c-api/number.rst: PyNumber_ToBase Doc/c-api/object.rst: PyObject_Bytes Doc/c-api/object.rst: PyObject_GenericGetAttr Doc/c-api/unicode.rst: PyUnicode_AsUTF32String Doc/c-api/unicode.rst: PyUnicode_DecodeMBCSStateful Doc/c-api/unicode.rst: PyUnicode_DecodeUTF32 Doc/c-api/unicode.rst: PyUnicode_DecodeUTF32Stateful Doc/c-api/unicode.rst: PyUnicode_DecodeUTF7 Doc/c-api/unicode.rst: PyUnicode_DecodeUTF7Stateful Doc/c-api/unicode.rst: PyUnicode_EncodeUTF32 Doc/c-api/unicode.rst: PyUnicode_EncodeUTF7 Doc/c-api/veryhigh.rst: PyEval_EvalCodeEx Doc/c-api/veryhigh.rst: PyEval_EvalFrame Doc/c-api/veryhigh.rst: PyEval_EvalFrameEx ---------- assignee: docs@python components: Documentation messages: 154877 nosy: baruch.sterin, docs@python priority: normal severity: normal status: open title: Documentation for some C APIs is missing clear specification of the type of reference they return type: behavior versions: Python 2.7 _______________________________________ Python tracker <report(a)bugs.python.org> <http://bugs.python.org/issue14189> _______________________________________

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[issue39090] Document various options for getting the absolute path from pathlib.Path objects
by Brett Cannon 17 Mar '21

17 Mar '21

New submission from Brett Cannon <brett(a)python.org>: The question on how best to get an absolute path from a pathlib.Path object keeps coming up (see https://bugs.python.org/issue29688, https://discuss.python.org/t/add-absolute-name-to-pathlib-path/2882/, and https://discuss.python.org/t/pathlib-absolute-vs-resolve/2573 as examples). As pointed out across those posts, getting the absolute path is surprisingly subtle and varied depending on your needs. As such we should probably add a section somewhere in the pathlib docs explaining the various ways and why you would choose one over the other. ---------- assignee: docs@python components: Documentation messages: 358638 nosy: brett.cannon, docs@python priority: normal severity: normal stage: needs patch status: open title: Document various options for getting the absolute path from pathlib.Path objects type: enhancement _______________________________________ Python tracker <report(a)bugs.python.org> <https://bugs.python.org/issue39090> _______________________________________

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[issue29688] Document Path.absolute
by Jim Fasarakis-Hilliard 17 Mar '21

17 Mar '21

New submission from Jim Fasarakis-Hilliard: Method absolute of Path objects lacked documentation, proposed PR adds relevant method to docs. ---------- assignee: docs@python components: Documentation messages: 288767 nosy: Jim Fasarakis-Hilliard, docs@python priority: normal severity: normal status: open title: Document Path.absolute versions: Python 3.5, Python 3.6, Python 3.7 _______________________________________ Python tracker <report(a)bugs.python.org> <http://bugs.python.org/issue29688> _______________________________________

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[issue32553] venv says to use python3 which does not exist in 3.6.4
by Paul Watson 17 Mar '21

17 Mar '21

New submission from Paul Watson <paul.hermeneutic(a)gmail.com>: The 3.6.4 documentation on venv specifies using 'python3', but no python3 executable is in the 3.6.4 kit. https://docs.python.org/3/library/venv.html?highlight=venv#module-venv ---------- assignee: docs@python components: Documentation messages: 309943 nosy: Paul Watson, docs@python priority: normal severity: normal status: open title: venv says to use python3 which does not exist in 3.6.4 type: enhancement versions: Python 3.6 _______________________________________ Python tracker <report(a)bugs.python.org> <https://bugs.python.org/issue32553> _______________________________________

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[issue15533] subprocess.Popen(cwd) documentation
by Chris Jerdonek 16 Mar '21

16 Mar '21

New submission from Chris Jerdonek: The sentence describing Popen()'s cwd argument in the subprocess documentation seems reversed to me: http://docs.python.org/dev/library/subprocess.html#subprocess.Popen It says, "If cwd is not None, the child’s current directory will be changed to cwd before it is executed. Note that this directory is not considered when searching the executable, so you can’t specify the program’s path relative to cwd." However, when cwd is not None, it seems like you *must* specify the program's path relative to cwd. For example, when running a script containing the following using `./python.exe` from a source checkout-- p = Popen(['./python.exe', '-V'], stdout=PIPE, stderr=PIPE, cwd='temp') you get an: "OSError: [Errno 2] No such file or directory." In contrast, when you *do* specify the program's path relative to cwd, it works-- p = Popen(['../python.exe', '-V'], stdout=PIPE, stderr=PIPE, cwd='temp') Issue 6374 seems to have made the same point in its second bullet, but the issue was closed without addressing that part of it. ---------- assignee: docs@python components: Documentation keywords: easy messages: 167194 nosy: cjerdonek, docs@python priority: normal severity: normal status: open title: subprocess.Popen(cwd) documentation versions: Python 2.7, Python 3.3 _______________________________________ Python tracker <report(a)bugs.python.org> <http://bugs.python.org/issue15533> _______________________________________

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[issue31665] Edit "Setting [windows] environmental variables"
by Terry J. Reedy 15 Mar '21

15 Mar '21

New submission from Terry J. Reedy <tjreedy(a)udel.edu>: Python Setup and Usage, 3.3.1. Excursus: Setting environment variables https://docs.python.org/3/using/windows.html#excursus-setting-environment-v… The word 'excursus' is so rare and archaic that this is my first encounter with it. Could we drop it? The last paragraph starts with "To permanently modify the default environment variables, click Start and search for ‘edit environment variables’,". This part is fine on Windows 10 as it brings up "Edit the system environment variables" and "Edit environmental variables for your account". Both take one to an Environmental variables dialog. The former requires than one be or become an admin user (via UAC dialog). The paragraph continues "or open System properties, Advanced system settings and click the Environment Variables button. In this dialog, you can add or modify User and System variables. To change System variables, you need non-restricted access to your machine (i.e. Administrator rights)." On Windows 10, at least, this is confusing or wrong. Control Panel has 'System' linked to the System dialog. This has 'Advanced systems settings' linked to System Properties, but one only get there by being or becoming (via UAC) an admin user. This has the Environmental Properties button mentioned above. It opens Environmental Variables for the admin user you are or are acting as. This route cannot change EVs for non-admin users. I have the impression that this has changed since Win 7. ---------- assignee: docs@python components: Documentation, Windows messages: 303560 nosy: docs@python, paul.moore, steve.dower, terry.reedy, tim.golden, zach.ware priority: normal severity: normal stage: needs patch status: open title: Edit "Setting [windows] environmental variables" type: behavior versions: Python 3.6, Python 3.7 _______________________________________ Python tracker <report(a)bugs.python.org> <https://bugs.python.org/issue31665> _______________________________________

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[issue29586] Cannot run pip in fresh install of py 3.5.3
by Adrian Chan 15 Mar '21

15 Mar '21

New submission from Adrian Chan: I uninstalled python 2.7 and 3.4, then performed a fresh install of 3.5.3. Running pip with `python -m pip` as per https://docs.python.org/3.5/installing gives the following error: C:\Python\Python35-32\python.exe: No module named pip.__main__; 'pip' is a package and cannot be directly executed Installation details: * win 7 64 bit. * python 3.5.3 32 bit. * chose options for pip, tcl/tk/idle, test suite, py launcher, shortcuts, add to env, precompile std lib. * installed to non-standard directory. ---------- assignee: docs@python components: Documentation, Installation, Windows messages: 287986 nosy: Adrian Chan, docs@python, paul.moore, steve.dower, tim.golden, zach.ware priority: normal severity: normal status: open title: Cannot run pip in fresh install of py 3.5.3 type: behavior versions: Python 3.5 _______________________________________ Python tracker <report(a)bugs.python.org> <http://bugs.python.org/issue29586> _______________________________________

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[issue31472] "Emulating callable objects" documentation misleading
by Nathan Marrow 14 Mar '21

14 Mar '21

New submission from Nathan Marrow: The documentation for emulating callable objects with __call__ seems to imply only positional arguments are supported. For instance, it says __call__ is "object.__call__(self[, args…])" and describes: Called when the instance is “called” as a function; if this method is defined, x(arg1, arg2, ...) is a shorthand for x.__call__(arg1, arg2, ...). When it should be something like (Not sure exactly what the syntax would be here): "object.__call__(self[, args…] [,**kwargs...])" Called when the instance is “called” as a function; if this method is defined, x(arg1, arg2, ..., arg3=arg3) is a shorthand for x.__call__(arg1, arg2, ..., arg3=arg3). ---------- assignee: docs@python components: Documentation messages: 302185 nosy: docs@python, nmarrow priority: normal severity: normal status: open title: "Emulating callable objects" documentation misleading versions: Python 2.7, Python 3.3, Python 3.4, Python 3.5, Python 3.6, Python 3.7 _______________________________________ Python tracker <report(a)bugs.python.org> <https://bugs.python.org/issue31472> _______________________________________

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