https://medium.com/@_kaki_/python-notes-2-%E5%85%A5%E9%96%80-%E7%92%B0%E5%A2%83%E5%AE%89%E8%A3%9D2-anaconda%E4%BB%8B%E7%B4%B9%E8%88%87%E5%AE%89%E8%A3%9D-5e34b5717862