参考这里
卸载旧版本python3
sudo apt-get --purge remove python3.4
下载并解压缩python3.9.4源码包
安装依赖包（可能还会有其他的包或重复的包）：
sudo apt-get update -y && sudo apt-get install -y gcc make build-essential software-properties-common libssl-dev zlib1g-dev libbz2-dev libreadline-dev libsqlite3-dev wget curl llvm libncurses5-dev libncursesw5-dev xz-utils tk-dev libffi-dev liblzma-dev libgdbm-dev libnss3-dev python-openssl git
编译安装：
./configure --prefix=/usr/local/python-3.9.4 --enable-optimizations
make && sudo make install
