Installing local packages with Python virtualenv --system-site-packages

Create the virtual environment without the --system-site-packages switch. After the environment was created go to the folder the environment was created in. It should have a file pyvenv.cfg. Edit this file. It has (among other text) a line

include-system-site-packages = false

Change this line to:

include-system-site-packages = true

Activate the environment. Module installations will now go to the virtual environment and the system site packages are visible too.

With Python 3.8, it seems --system-site-packages work as expected:

python3 -m venv --system-site-packages myProject
cat myProject/pyvenv.cfg 

home = /usr/bin
include-system-site-packages = true
version = 3.8.5

After installation astroid, isort, wrapt, I got:

pip list -v
Package                Version              Location                                                Installer
---------------------- -------------------- ------------------------------------------------------- ---------
apturl                 0.5.2                /usr/lib/python3/dist-packages                                   
astroid                2.4.2                /home/to/no/MR/auto-gen/lib/python3.8/site-packages pip      
isort                  5.6.4                /home/to/no/MR/auto-gen/lib/python3.8/site-packages pip      
jedi                   0.15.2               /usr/lib/python3/dist-packages                                   
keyring                18.0.1               /usr/lib/python3/dist-packages                                   
wrapt                  1.12.1               /home/to/no/MR/auto-gen/lib/python3.8/site-packages pip

Already installed 'system' packages are taken from /usr/lib/python3/dist-packages while locally (venv) installed packages from: /home/to/no/MR/auto-gen/lib/python3.8/site-packages