How can I 'clean up' a virtualenv?

The following works for me (can be executed from any Python 3.6 virtualenv):

virtualenv --clear your-env-name

Where your-env-name could be:

• Path to the virtual environment (relative from current directory or absolute)
• Or if you use virtualenv-wrapper, just the name of the environment

To uninstall every package (including dependencies) you can freeze the requirements and then pass them to pip uninstall:

pip freeze > to-uninstall.txt
pip uninstall -r to-uninstall.txt

This answer may be just what you need.

You can install and use the pip-autoremove utility to remove a package plus unused dependencies.

# install pip-autoremove 
pip install pip-autoremove
# remove "somepackage" plus its dependencies: 
pip-autoremove somepackage -y