https://www.jianshu.com/p/51140800e8b4
ubuntu16.04中将python3设置为默认
转自https://www.cnblogs.com/Jeb15/p/6080331.html
直接执行这两个命令即可:
/usr/bin/python2 100 sudo update-alternatives --install /usr/bin/python python /usr/bin/python3 150 ```
安装依赖包(须在虚拟环境中)
pip freeze > requirements.txt
pip install -r requirements.txt