upgrade python3 ubuntu code example

Example 1: update ubuntu to python 3.85

sudo apt-get install python3.8

Example 2: ubuntu install python

# first do:
sudo apt-get update
# after do:
sudo apt-get install python3.6
# then it should be installed

Example 3: update python ubuntu

$ sudo apt update -y
$ sudo apt install python3.7

Example 4: update ubuntu to python 3.85

sudo update-alternatives --config python3

Example 5: update ubuntu to python 3.85

apt-get update