python 3多版本共存

http://npm.taobao.org/mirrors/python/3.7.9/Python-3.7.9.tgz
tar -zxvf Python-3.7.9.tgz
./configure --prefix=/usr/local/python3.7
make & make install 
/usr/local/python3.7/bin/python3 -m venv venv