I have a few projects in PyCharm, each with its own virtual environment.
Quite often, I add packages to these virtual environments using the CLI, mainly with python setup.py develop
from another local package.
The new package appear in Preferences -> Project -> Project Interpreter
and the calls to the newly-installed packages runs, but the imports still appear as erroneous, which drives me nuts:
How do I refresh the virtual environment
For PyCharm 2018.3.4, I solved this by verifying that the correct source locations are specified under File/Settings/Project::Project Structure. All of the valid source directories should be marked as "Sources" and the venv directory should marked as Excluded, at least that's what worked for me.