My system is Archlinux. My project will use NumPy, and my project is in a virtual environment created by virtualenv.
As it is difficult to install NumPy by pip, I install it by Pacman:
sudo pacman -S python-scikit-learn
But how can I use it in virtualenv?
You can create the virtualenv with the --system-site-packages switch to use system-wide packages in addition to the ones installed in the stdlib.