宝塔面板在Ubuntu18.04+Python3下，基本可以秒装LNMP，不过ubuntu默认还是python2.7，现在我们切换成3
1.安装Python3及pip3
sudo apt-get install python3
sudo apt install python3-pip
2.将Python3设置为默认
sudo update-alternatives --install /usr/bin/python python /usr/bin/python2 100
sudo update-alternatives --install /usr/bin/python python /usr/bin/python3 150
3.验证
python --version
Python 3.6.5 #显示这个就说明切换成功
4.Python2、3切换
sudo update-alternatives --config python
会出现如下界面
There are 2 choices for the alternative python (providing /usr/bin/python).
Selection Path Priority Status
------------------------------------------------------------
* 0 /usr/bin/python3 150 auto mode
1 /usr/bin/python2 100 manual mode
2 /usr/bin/python3 150 manual mode
Press <enter> to keep the current choice[*], or type selection number:
输入1，即可切换python2；输入0，即可切换python3，检查一下
python --version
Python 2.7.15rc1
