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Document absoluteness of sys.executable #57611
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GitHub fields:
assignee = None
closed_at = <Date 2012-02-02.19:30:22.171>
created_at = <Date 2011-11-14.16:50:37.246>
labels = ['docs']
title = 'Document absoluteness of sys.executable'
updated_at = <Date 2016-07-12.03:05:43.826>
user = 'https://github.com/merwok'bugs.python.org fields:
activity = <Date 2016-07-12.03:05:43.826>
actor = 'ned.deily'
assignee = 'docs@python'
closed = True
closed_date = <Date 2012-02-02.19:30:22.171>
closer = 'python-dev'
components = ['Documentation']
creation = <Date 2011-11-14.16:50:37.246>
creator = 'eric.araujo'
dependencies = []
files = ['23738', '23958', '24380']
hgrepos = []
issue_num = 13402
keywords = ['patch']
message_count = 20.0
messages = ['147609', '148006', '148029', '148042', '148043', '148317', '148355', '148356', '148357', '149468', '149483', '149511', '150460', '152403', '152473', '270210', '270217', '270222', '270223', '270224']
nosy_count = 16.0
nosy_names = ['ronaldoussoren', 'pitrou', 'vstinner', 'pjenvey', 'schmir', 'ned.deily', 'eric.araujo', 'dino.viehland', 'eli.bendersky', 'flox', 'docs@python', 'python-dev', 'eric.snow', 'petri.lehtinen', 'eryksun', 'blarsen']
pr_nums = []
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue13402'
versions = ['Python 2.7', 'Python 3.2', 'Python 3.3']
Activity
merwok commentedon Nov 14, 2011
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.)
akheron commentedon Nov 20, 2011
Attached a patch.
elibendersky commentedon Nov 21, 2011
LGTM
merwok commentedon Nov 21, 2011
Patch looks good, but are you 100% sure that sys.executable is always absolute? (On all OSes, under multiprocessing, etc?)
akheron commentedon Nov 21, 2011
Éric Araujo wrote:
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.
merwok commentedon Nov 25, 2011
This is the bug I was thinking about: bpo-7774. Adding some people from that discussion to nosy.
pitrou commentedon Nov 25, 2011
LGTM too.
You could also add a test to test_sys ensuring that sys.executable is always executable.
vstinner commentedon Nov 25, 2011
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 bpo-7774. The fact that sys.executable can be empty should be documented.
pitrou commentedon Nov 25, 2011
Er, yes, that's what I meant. Sorry.
akheron commentedon Dec 14, 2011
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.
pjenvey commentedon Dec 14, 2011
sys.executable can be None on Jython (and I believe IronPython) when ran in an 'embedded' mode
akheron commentedon Dec 15, 2011
In CPython, embedding doesn't change the behavior.
merwok commentedon Jan 2, 2012
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)).
akheron commentedon Jan 31, 2012
Attached one more patch. The documentation now also mentions None as a possible value.
python-dev commentedon Feb 2, 2012
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
bradlarsen commentedon Jul 11, 2016
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/python2.7Also 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/python3.5eryksun commentedon Jul 12, 2016
"/opt/local/bin/../bin/python2.7" is an absolute path.
>>> os.path.isabs('/opt/local/bin/../bin/python2.7') TrueIt's not relative to the working directory.
ned-deily commentedon Jul 12, 2016
@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.
bradlarsen commentedon Jul 12, 2016
@eryksun, you are right! The output is an absolute path as far as
os.path.isabsis 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_systest 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:Yes, /opt/local/bin/../bin/python3.5 is an absolute path as far as
os.path.isabsis concerned, butos.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?ned-deily commentedon Jul 12, 2016
@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.