apt - "Unable to locate package python-pip" When trying to install from fresh 18.04 install

I was following a tutorial online for python and it had me do this:

akclark@enceladus:~$ pip install virtualenv

But I got the following:

Command 'pip' not found, but can be installed with:
sudo apt install python-pip

Easy enough, right? So I try it..

akclark@enceladus:~$ sudo apt install python-pip

But I get an error...

Reading package lists... Done
Building dependency tree Reading state information... Done
E: Unable to locate package python-pip

What am I doing wrong?

EDIT: Per Comments I have tried sudo apt update

EDIT2: I tried apt-cache madison python-pip and got

N: Unable to locate package python-pip

EDIT3: grep '^deb ' /etc/apt/sources.list showed

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

You have to enable universe category which contains python-pip package.

Open /etc/apt/sources.list using an editor, for example nano:

sudo nano /etc/apt/sources.list

then add universe at the end of each line, like this:

deb http://archive.ubuntu.com/ubuntu bionic main universe
deb http://archive.ubuntu.com/ubuntu bionic-security main universe
deb http://archive.ubuntu.com/ubuntu bionic-updates main universe

Press Ctrl+O to save the file.

then run:

sudo apt update

and finally:

sudo apt install python-pip