[issue32444] python -m venv has incongruous behavor creating binaries

[R. David Murray]

R. David Murray  added the comment:

This is a feature that actually supports your use case, as well as the use 
cases of those who *don't* want to strap the python version: you get what you 
ask for.  If you call venv with 'python3', you get a venv that will use your 
new python if you upgrade your python, but if you call it with python3.x, you 
will get a venv that will *not* upgrade, which is exactly what you want for 
your use case.

--
nosy: +r.david.murray
resolution:  -> not a bug
stage:  -> resolved
status: open -> closed
versions: +Python 3.7 -Python 3.5

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[issue32444] python -m venv has incongruous behavor creating binaries

[Corey Seliger]

Corey Seliger  added the comment:

Here is the write-up I posted over on the pyenv issues page:

This is apparently a behavior issue in the way venv works. Not only does this 
impact 3.6.x, I also confirmed that the same issue occurs with venv in general 
using the stock 3.5 Python that comes with Ubuntu 16.04.

The trouble is at 3.6/Lib/venv/__init__.py:111. Starting at line 111:

if sys.platform == 'darwin' and '__PYVENV_LAUNCHER__' in env:
executable = os.environ['__PYVENV_LAUNCHER__']
else:
executable = sys.executable
dirname, exename = os.path.split(os.path.abspath(executable))
context.executable = executable

This carries down to the setup_python method starting at line 187 
(3.6/Lib/venv/__init__.py:187). It takes whatever executable that is called as 
the source, and then creates the others based on a hard coded list (e.g. python 
and python3).

def setup_python(self, context):
"""
Set up a Python executable in the environment.
:param context: The information for the environment creation request
being processed.
"""
binpath = context.bin_path
path = context.env_exe
copier = self.symlink_or_copy
copier(context.executable, path)
dirname = context.python_dir
if os.name != 'nt':
if not os.path.islink(path):
os.chmod(path, 0o755)
for suffix in ('python', 'python3'):
path = os.path.join(binpath, suffix)
if not os.path.exists(path):
# Issue 18807: make copies if
# symlinks are not wanted
copier(context.env_exe, path, relative_symlinks_ok=True)
if not os.path.islink(path):
os.chmod(path, 0o755)
else:
subdir = 'DLLs'
include = self.include_binary
files = [f for f in os.listdir(dirname) if include(f)]
for f in files:
src = os.path.join(dirname, f)
dst = os.path.join(binpath, f)
if dst != context.env_exe:  # already done, above
copier(src, dst)
dirname = os.path.join(dirname, subdir)
if os.path.isdir(dirname):
files = [f for f in os.listdir(dirname) if include(f)]
for f in files:
src = os.path.join(dirname, f)
dst = os.path.join(binpath, f)
copier(src, dst)
# copy init.tcl over
for root, dirs, files in os.walk(context.python_dir):
if 'init.tcl' in files:
tcldir = os.path.basename(root)
tcldir = os.path.join(context.env_dir, 'Lib', tcldir)
if not os.path.exists(tcldir):
os.makedirs(tcldir)
src = os.path.join(root, 'init.tcl')
dst = os.path.join(tcldir, 'init.tcl')
shutil.copyfile(src, dst)
break


If you don't call -m venv as python3.X, you will never get that binary in the 
bin directory.

--

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[issue32444] python -m venv has incongruous behavor creating binaries

[Corey Seliger]

New submission from Corey Seliger :

The venv module does not evenly create the necessary binaries/symlinks when 
building virtualenvs. If you call venv like this:

seliger@core:~/venvs$ python3 -m venv venvA

seliger@core:~/venvs$ ls -l venvA/bin/
total 32
-rw-r--r-- 1 seliger seliger 2143 Dec 28 21:29 activate
-rw-r--r-- 1 seliger seliger 1259 Dec 28 21:29 activate.csh
-rw-r--r-- 1 seliger seliger 2397 Dec 28 21:29 activate.fish
-rwxrwxr-x 1 seliger seliger  254 Dec 28 21:29 easy_install
-rwxrwxr-x 1 seliger seliger  254 Dec 28 21:29 easy_install-3.5
-rwxrwxr-x 1 seliger seliger  226 Dec 28 21:29 pip
-rwxrwxr-x 1 seliger seliger  226 Dec 28 21:29 pip3
-rwxrwxr-x 1 seliger seliger  226 Dec 28 21:29 pip3.5
lrwxrwxrwx 1 seliger seliger7 Dec 28 21:29 python -> python3
lrwxrwxrwx 1 seliger seliger   16 Dec 28 21:29 python3 -> /usr/bin/python3

...you do not end up with a "python3.5" binary. 

However, if you call venv like this:

seliger@core:~/venvs$ python3.5 -m venv venvB

seliger@core:~/venvs$ ls -l venvB/bin
total 32
-rw-r--r-- 1 seliger seliger 2143 Dec 28 21:29 activate
-rw-r--r-- 1 seliger seliger 1259 Dec 28 21:29 activate.csh
-rw-r--r-- 1 seliger seliger 2397 Dec 28 21:29 activate.fish
-rwxrwxr-x 1 seliger seliger  256 Dec 28 21:29 easy_install
-rwxrwxr-x 1 seliger seliger  256 Dec 28 21:29 easy_install-3.5
-rwxrwxr-x 1 seliger seliger  228 Dec 28 21:29 pip
-rwxrwxr-x 1 seliger seliger  228 Dec 28 21:29 pip3
-rwxrwxr-x 1 seliger seliger  228 Dec 28 21:29 pip3.5
lrwxrwxrwx 1 seliger seliger9 Dec 28 21:29 python -> python3.5
lrwxrwxrwx 1 seliger seliger9 Dec 28 21:29 python3 -> python3.5
lrwxrwxrwx 1 seliger seliger   18 Dec 28 21:29 python3.5 -> /usr/bin/python3.5

...you DO get the necessary python3.5 binary. Some vendors are making it a 
requirement to call a specific pythonX.Y binary to ensure compatibility. One 
such example is the serverless framework when deploying to Amazon Web Services. 
Another example is the useful pyenv utility that manages full Python builds and 
virtualenvs. When it depends upon venv, it exhibits the same behavior. I 
submitted a patch workaround to force calling venv using pythonX.Y, but this 
really seems like an issue with the venv module itself.

The expected behavior should be that venv generates all three binaries (python, 
python3, and python3.5) regardless of how the python command was invoked.

I am able to reproduce this on Python 3.5 and 3.6. I could not find any other 
similar references in searching the bug system.

--
components: Library (Lib)
messages: 309157
nosy: seliger
priority: normal
severity: normal
status: open
title: python -m venv has incongruous behavor creating binaries
type: behavior
versions: Python 3.5, Python 3.6

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