所以我有 python 3.8 和 pip ，但我也想安装稳定的 python 3.7 和 pip 。但是当我尝试时
sudo apt-get install python3.7
它说包不可用但被称为另一个包。请帮助错误：
Reading package lists... Done
Building dependency tree
Reading state information... Done
Package python3.7 is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source
E: Package 'python3.7' has no installation candidate