[issue13402] Document absoluteness of sys.executable

[Ned Deily]

Ned Deily added the comment:

@blarsen, OK, but if you want to pursue this, please open a new issue against 
the current versions.  This issue was closed years ago and against earlier 
versions so your comments will not get acted on.

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[issue13402] Document absoluteness of sys.executable

[Brad Larsen]

Brad Larsen added the comment:

@eryksun, you are right!  The output *is* an absolute path as far as 
`os.path.isabs` is concerned.

@ned.deily, you are right about my example --- I transcribed it wrong, and it 
should be `-c`.

The system in question is not a Mac OS system, but a Linux system with newer 
Python versions than what come with the system installed to /opt/local.  These 
are compiled from source, but without any modifications.

I'm commenting here because I'm seeing the `test_sys` test from the regression 
suite fail in a slightly modified version of Python that ships with a product.  
In particular, in Lib/test/test_sys.py around line 640, we have this:

@unittest.skipIf(sys.base_prefix != sys.prefix,
 'Test is not venv-compatible')
def test_executable(self):
# sys.executable should be absolute
self.assertEqual(os.path.abspath(sys.executable), sys.executable)

Yes, /opt/local/bin/../bin/python3.5 is an absolute path as far as 
`os.path.isabs` is concerned, but 
`os.path.abspath('/opt/local/bin/../bin/python3.5')` gives 
'/opt/local/bin/python3.5', and the test fails.  So maybe the documentation is 
fine but the test is wrong?

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[issue13402] Document absoluteness of sys.executable

[Ned Deily]

Ned Deily added the comment:

@blarsen, and there's something strange about your example.  '-m' won't work 
with a real python executable, presumably you meant '-c'.  And judging from the 
paths involved, I'm guessing you are using MacPorts on OS X.  With either 
MacPorts or any other OS X framework build, you wouldn't see results like that 
with -c.

 ../bin/python3.5 -c 'import sys; print(sys.executable)'
/opt/local/bin/python3.5
../bin/python2.7 -c 'import sys; print(sys.executable)'
/opt/local/Library/Frameworks/Python.framework/Versions/2.7/Resources/Python.app/Contents/MacOS/Python

So I'm guessing what's in ../bin/python3.7 and ../bin/python3.5 is something 
other than the normal python bootstrap binaries.

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nosy: +ned.deily

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[issue13402] Document absoluteness of sys.executable

[Eryk Sun]

Eryk Sun added the comment:

"/opt/local/bin/../bin/python2.7" is an absolute path. 

>>> os.path.isabs('/opt/local/bin/../bin/python2.7')
True

It's not relative to the working directory.

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nosy: +eryksun

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[issue13402] Document absoluteness of sys.executable

[Brad Larsen]

Brad Larsen added the comment:

It looks like sys.executable is *not* always an absolute path.  In Python 2.7:

$ which python2.7
/opt/local/bin/python2.7
$ cd /opt/local/bin
$ ../bin/python2.7 -m 'import sys; print(sys.executable)'
/opt/local/bin/../bin/python2.7

Also in Python 3.5:

$ which python3.5
/opt/local/bin/python3.5
$ cd /opt/local/bin
$ ../bin/python3.5 -m 'import sys; print(sys.executable)'
/opt/local/bin/../bin/python3.5

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nosy: +blarsen

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[issue13402] Document absoluteness of sys.executable

[Roundup Robot]

Roundup Robot  added the comment:

New changeset fdcda5b74317 by Petri Lehtinen in branch '3.2':
Document absoluteness of sys.executable
http://hg.python.org/cpython/rev/fdcda5b74317

New changeset 8b591a86fc91 by Petri Lehtinen in branch 'default':
Merge branch 3.2
http://hg.python.org/cpython/rev/8b591a86fc91

New changeset c351536e804a by Petri Lehtinen in branch '2.7':
Document absoluteness of sys.executable
http://hg.python.org/cpython/rev/c351536e804a

--
nosy: +python-dev
resolution:  -> fixed
stage:  -> committed/rejected
status: open -> closed

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[issue13402] Document absoluteness of sys.executable

[Petri Lehtinen]

Petri Lehtinen  added the comment:

Attached one more patch. The documentation now also mentions None as a possible 
value.

--
Added file: http://bugs.python.org/file24380/issue13402_v3.patch

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[issue13402] Document absoluteness of sys.executable

[Éric Araujo]

Éric Araujo  added the comment:

This discussion seems relevant: 
http://mail.python.org/pipermail/python-dev/2006-March/062453.html (it talks 
about the meaning of sys.executable, special cases such as embedded Python and 
functions that implement it (so we can have a look at that code)).

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[issue13402] Document absoluteness of sys.executable

[Petri Lehtinen]

Petri Lehtinen  added the comment:

> sys.executable can be None on Jython (and I believe IronPython) when ran in 
> an 'embedded' mode

In CPython, embedding doesn't change the behavior.

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[issue13402] Document absoluteness of sys.executable

[Philip Jenvey]

Philip Jenvey  added the comment:

sys.executable can be None on Jython (and I believe IronPython) when ran in an 
'embedded' mode

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nosy: +dino.viehland, pjenvey

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[issue13402] Document absoluteness of sys.executable

[Petri Lehtinen]

Petri Lehtinen  added the comment:

Attaching an updated patch. The documentation now says that sys.executable may 
be an empty string. The patch also adds a test to make sure that sys.executable 
is absolute.

--
Added file: http://bugs.python.org/file23958/issue13402_v2.patch

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[issue13402] Document absoluteness of sys.executable

[Antoine Pitrou]

Antoine Pitrou  added the comment:

> > You could also add a test to test_sys ensuring that sys.executable
> > is always executable.
> 
> And that sys.executable is absolute?

Er, yes, that's what I meant. Sorry.

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[issue13402] Document absoluteness of sys.executable

[STINNER Victor]

STINNER Victor  added the comment:

> You could also add a test to test_sys ensuring that sys.executable
> is always executable.

And that sys.executable is absolute?

sys.executable is an empty string if sys.argv[0] has been changed and Python is 
unable to retrieve the real path to the Python executable. See the issue #7774. 
The fact that sys.executable can be empty should be documented.

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[issue13402] Document absoluteness of sys.executable

[Antoine Pitrou]

Antoine Pitrou  added the comment:

LGTM too.
You could also add a test to test_sys ensuring that sys.executable is always 
executable.

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[issue13402] Document absoluteness of sys.executable

[Éric Araujo]

Éric Araujo  added the comment:

This is the bug I was thinking about: #7774.  Adding some people from that 
discussion to nosy.

--
nosy: +flox, haypo, pitrou, ronaldoussoren, schmir

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[issue13402] Document absoluteness of sys.executable

[Eric Snow]

Changes by Eric Snow :


--
nosy: +eric.snow

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[issue13402] Document absoluteness of sys.executable

[Petri Lehtinen]

Petri Lehtinen  added the comment:

Éric Araujo wrote:
> Patch looks good, but are you 100% sure that sys.executable is
> always absolute? (On all OSes, under multiprocessing, etc?)

Well, its value is computed by a function named
Py_GetProgramFullPath(), so I'm quite sure. I had a quick look on what
the function is doing, but it was quite complicated. I can check it
better if needed.

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[issue13402] Document absoluteness of sys.executable

[Éric Araujo]

Éric Araujo  added the comment:

Patch looks good, but are you 100% sure that sys.executable is always absolute? 
 (On all OSes, under multiprocessing, etc?)

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[issue13402] Document absoluteness of sys.executable

[Eli Bendersky]

Eli Bendersky  added the comment:

LGTM

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nosy: +eli.bendersky

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[issue13402] Document absoluteness of sys.executable

[Petri Lehtinen]

Petri Lehtinen  added the comment:

Attached a patch.

--
keywords: +patch
Added file: http://bugs.python.org/file23738/issue13402.patch

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[issue13402] Document absoluteness of sys.executable

[Petri Lehtinen]

Changes by Petri Lehtinen :


--
nosy: +petri.lehtinen

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[issue13402] Document absoluteness of sys.executable

[Éric Araujo]

New submission from Éric Araujo :

I wanted to know if sys.executable was always an absolute path but the doc does 
not talk about that.

(My use case is that I’d like to reload a process and I wonder if I can call 
os.execve or if I need to use os.execvpe.)

--
assignee: docs@python
components: Documentation
messages: 147609
nosy: docs@python, eric.araujo
priority: normal
severity: normal
status: open
title: Document absoluteness of sys.executable
versions: Python 2.7, Python 3.2, Python 3.3

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