I strongly recommend you to use virtual environments for python package installation. With virtualenv, you prevent any package conflict and total isolation from your python related userland commands.
To delete all your package follow this;
It's possible to uninstall packages installed with --user
flag. This one worked for me;
pip freeze --user | xargs pip uninstall -y
For python 3;
pip3 freeze --user | xargs pip3 uninstall -y
But somehow these commands don't uninstall setuptools and pip. After those commands (if you really want clean python) you may delete them with;
pip uninstall setuptools && pip uninstall pip