Install Python (Ubuntu 20.04 LTS)

1. update apt

$ sudo apt update -y
$ sudo apt upgrade -y
$ sudo apt install software-properties-common

2. Add deadnsakes PPA

$ sudo add-apt-repository ppa:deadsnakes/ppa

3. Install python 3.9

$ sudo apt install python3.9

4. 설치 완료

$ which python3.9
/usr/bin/python3.9

$ python3.9 --version
Python 3.9.6