How to create a new virtual environment based on an existing sage installation

[Maarten Derickx]

Hi All,

I am wondering what the best way is to create a new virtual environment where I can import stuff from an already existing sage installation:

I tried the following using sage 9.5.beta9

$ sage -python3 -m venv --system-site-packages venv
$ source venv/bin/activate
(venv) $ python3
Python 3.9.9 (main, Dec 25 2021, 18:25:51)
[GCC 9.3.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> from sage.all import *
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/scratch/home/mderickx/sages/sage/local/var/lib/sage/venv-python3.9.9/lib/python3.9/site-packages/sage/all.py", line 126, in <module>
from sage.rings.all import *
File "/scratch/home/mderickx/sages/sage/local/var/lib/sage/venv-python3.9.9/lib/python3.9/site-packages/sage/rings/all.py", line 87, in <module>
...
...
File "sage/rings/polynomial/multi_polynomial_libsingular.pyx", line 1, in init sage.rings.polynomial.multi_polynomial_libsingular (build/cythonized/sage/rings/polynomial/multi_polynomial_libsingular.cpp:50020)
File "sage/libs/singular/singular.pyx", line 1558, in init sage.libs.singular.singular (build/cythonized/sage/libs/singular/singular.cpp:15747)
File "sage/libs/singular/singular.pyx", line 1525, in sage.libs.singular.singular.init_libsingular (build/cythonized/sage/libs/singular/singular.cpp:12865)
File "/scratch/home/mderickx/sages/sage/local/var/lib/sage/venv-python3.9.9/lib/python3.9/posixpath.py", line 152, in dirname
p = os.fspath(p)
TypeError: expected str, bytes or os.PathLike object, not NoneType

But as you can see this new venv is not created in such a way that sage the library is useable (probably because certain sage related environment variables are not set).

So what is the best way to get around this?

[Matthias Koeppe]

The particular error that you are running into comes from Singular not being in PATH.

Use "sage -sh" to enter a shell in which SAGE_LOCAL/bin has been added to PATH.

Then you can activate the venv as you did before.

[Matthias Koeppe]

https://trac.sagemath.org/ticket/33440 fixes the problem and is waiting for review.