我正在关注 python 的在线教程，它让我这样做：
akclark@enceladus:~$ pip install virtualenv
但我得到了以下信息：
Command 'pip' not found, but can be installed with:
sudo apt install python-pip
够简单了吧？所以我试试。。
akclark@enceladus:~$ sudo apt install python-pip
但我得到一个错误...
Reading package lists... Done
Building dependency tree Reading state information... Done
E: Unable to locate package python-pip
我究竟做错了什么？
编辑：根据我尝试过的评论 sudo apt update
EDIT2：我试过apt-cache madison python-pip了
N: Unable to locate package python-pip
EDIT3：grep '^deb ' /etc/apt/sources.list显示
deb http://archive.ubuntu.com/ubuntu bionic main
deb http://archive.ubuntu.com/ubuntu bionic-security main
deb http://archive.ubuntu.com/ubuntu bionic-updates main