python sys.executable inconsistency if called from cmd

python sys.executable inconsistency if called from cmd

[Lemke, Michael SF/HZA-ZIC2]

I don't know anything about python but want to use cygwin's
python from nodejs with npm-gyp. The npm-gyp module is trying to
find the python executable path from sys.executable and fails.
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? Is there a way around to make this work?

Re: python sys.executable inconsistency if called from cmd

[Andrey Repin]

Greetings, Lemke, Michael  SF/HZA-ZIC2!

> I don't know anything about python but want to use cygwin's
> python from nodejs with npm-gyp. The npm-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.

> 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.

> Is there a way around to make this work?

Yes, write scripts correctly, correctly translate paths.

See:
> FAQ:                  https://cygwin.com/faq/
> Documentation:        https://cygwin.com/docs.html

Specifically see `man cygpath`.

-- 
With best regards,
Andrey Repin
Wednesday, February 3, 2021 18:25:18

Sorry for my terrible english...

RE: python sys.executable inconsistency if called from cmd

[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:

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.

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

See above.

Re: python sys.executable inconsistency if called from cmd

[Marco Atzeri]

On 03.02.2021 17:17, Lemke, Michael SF/HZA-ZIC2 wrote:
> 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:
> 
> 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.
> 

Hi Michael,

do you know that python3.7 is also available in Cygwin ?
All versions availabe are:

$ ls  /usr/bin/python3* | grep -v config
/usr/bin/python3
/usr/bin/python3.6
/usr/bin/python3.6m.exe
/usr/bin/python3.7
/usr/bin/python3.7m.exe
/usr/bin/python3.8.exe


Where have you installed the node-gyp v5.1.0 and how ?

Regards
Marco

Re: python sys.executable inconsistency if called from cmd

[Andrey Repin]

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...