An embedded Python system does not automatically pick up Python
virtual environments. It is supposed to setup its own environment. Janus
is sensitive to Python venv environments. Running under such as
environment is assumed if the environment variable
VIRTUAL_ENV points at a directory that holds a file
pyvenv.cfg. If the virtual environment is detected, the
actions in the list below are taken.3This
is based on observing how Python 3.10 on Linux responds to being used
inside a virtual environment. We do not know whether this covers all
platforms and versions.
- Initialize Python using the
-I flag to indicate
isolation.
- Set
sys.prefix to the value of the VIRTUAL_ENV
environment variable.
- Remove all directories with base name
site-packages or
dist-packages from sys.path.4Note
that -I only removes the personal packages directory, while
the Python executable removes all, so we do the same.
- Add
$VIRTUAL_ENV/lib/pythonX.Y/site-packages to
sys.path, where X and Y are the major
and minor version numbers of the embedded Python library. If this
directory does not exist we print a diagnostic warning.
- Add a message to py_version/0
that indicates we are using a virtual environment and from which
directory.
