Python 3 comes pre-installed with Ubuntu 18.04 LTS. Follow additional steps to update:
Step 1: Update and Upgrade. To ensure shipped version of Python is up to date.
$ sudo apt update
$ sudo apt -y upgrade
Step 2: Check which version of Python installed using below command.
$ python3 -V
Step 3: Install pip, a tool to manage libraties or modules.
$sudo apt install -y python3-pip