Python 3.x版本使用pip3，它会把你想下载的包放到usr/local/lib/python3.5/dist-packages/下，而非usr/local/lib/python2.7/dist-packages/下

sudo apt-get install python3-pip

sudo pip3 install --upgrade pip

sudo pip3 install numpy

sudo pip3 install scipy

sudo pip3 install matplotlib

Ubuntu 16.04 同时使用python3.5