Re: python sys.executable inconsistency if called from cmd

[Andrey Repin <anrdaemon@yandex.ru>]

Greetings, Lemke, Michael  SF/HZA-ZIC2!

> On Wednesday, February 3, 2021 4:28 PM Andrey Repin wrote:
>>Greetings, Lemke, Michael  SF/HZA-ZIC2!
>>
>>> I don't know anything about python but want to use cygwin's
>>> python from nodejs npm with node-gyp. The node-gyp module is trying to
>>> find the python executable path from sys.executable and fails.
>>
>>If that's true, then it should be fixed upstream.

> Good to know but I doubt that they will. For those who need this -
> here is a workaround for node-gyp v5.1.0 I just found:

Precedently, MS Visual Studio Code comes with a wrapper, that deals with
Cygwin just fine so far.

> cygwin> mkdir /c/Python37
> cygwin> ln `which python3.6m` /c/Python37/python.exe

> I aware of the version clash here but c:\Python37 is one of a
> few explicit locations this node-gyp looks at. Doesn't seem
> confused if the versions don't match. The file you link to 
> must be the actual Cygwin executable not any of the python 
> links in /bin.

>>
>>> While investigating this I found this to me quite inconsistent
>>> behavior:
>>
>>> cygwin> /bin/python3.6m.exe -c 'import sys; print(sys.executable);'
>>> /bin/python3.6m
>>
>>> cygwin> python3.6m -c 'import sys; print(sys.executable);'
>>> /usr/bin/python3.6m
>>
>>> cygwin> python3.6 -c 'import sys; print(sys.executable);'
>>> /usr/bin/python3.6
>>
>>> cygwin> python3.6m.exe -c 'import sys; print(sys.executable);'
>>> /usr/bin/python3.6m
>>
>>
>>> cmd> c:/MyStuff/NCygwin64/bin/python3.6m.exe -c 'import sys; print(sys.executable);'
>>> /usr/bin/python3.6m
>>
>>> cmd> rem add cygwin path to Windows:
>>> cmd> path %PATH%;c:\MYSTUFF\ncygwin64\bin
>>
>>> cmd> python3.6m.exe -c 'import sys; print(sys.executable);'
>>> /c/MYSTUFF/ncygwin64/bin/python3.6m
>>
>>> With CMD I'll never get an executable that actually works from cmd.
>>> Is this expected?
>>
>>Yes. This is Cygwin, not Windows CMD.

> Sure but python seems to start just fine under cmd and it does do
> some gyrations with sys.executable dependent on calling environment.
> So this looks somewhat fishy to me.

Nothing "phishy".
Cygwin programs work in POSIX environment, this is no surprise that paths you
see in Cygwin are POSIX, unless specifically converted to Windows paths.
At the same time, Cygwin programs are Windows executables. Would be surprising
if they would NOT start by themselves.
Said that, it is generally not expected that Cygwin programs would accept
native Windows paths, although in many cases, they do just fine.
The reverse also applies. Windows programs don't understand Cygwin paths and
there's no simple way to convert them outside the given Cygwin environment.
Use cygpath.

>>> Is there a way around to make this work?
>>
>>Yes, write scripts correctly, correctly translate paths.

> See above.


-- 
With best regards,
Andrey Repin
Wednesday, February 3, 2021 20:03:43

Sorry for my terrible english...