源码安装，从https://www.python.org/ftp/python/官网下载，一般情况下，从源码安装错误会极少，强烈推荐。
# 获取 https://www.python.org/ftp/python/
$ wget https://www.python.org/ftp/python/3.6.5/Python-3.6.5.tgz
# 解压、安装
$ tar zxvf Python-3.6.5.tgz -C /home/
$ cd Python-3.6.5
$ ./configure --prefix=/usr/local/python3
$ make && make install
# 创建软链接
$ ln -s /usr/local/python3/bin/python3 /usr/bin/python3
$ ln -s /usr/local/python3/bin/pip3 /usr/bin/pip3
# 更新pip3到最新版本
$ pip3 install --upgrade pip
# 测试python3是否安装成功
$ python3
Python 3.6.5
# 安装所需的python库
$ pip3 install PyMySQL
$ pip3 install pymongo