失败尝试(通过apt安装)
sudo add-apt-repository ppa:deadsnakes/ppa
...
Error: retrieving gpg key timed out
查资料发现ppa:deadsnakes/ppa不再维护旧版本ubuntu
成功尝试（从源码编译）
速度挺快的
py_version=3.9.9 # 指定 Python 版本
sudo apt install -y gcc make openssl libssl-dev zlib1g zlib1g-dev libffi-dev # 安装编译环境
curl -O https://www.python.org/ftp/python/${py_version}/Python-${py_version}.tgz
tar -zxvf Python-${py_version}.tgz
cd Python-${py_version}
./configure --prefix=/usr/local/python/Python-${py_version} --with-ensurepip=install
make
sudo make install
cd ..
sudo rm -rf Python-${py_version} Python-${py_version}.tgz
sudo ln -s /usr/local/python/Python-${py_version}/bin/* /usr/local/bin/
参考链接：https://blog.csdn.net/qq_35952638/article/details/131070107
