Section 1: Upgrading Python on Windows

To upgrade Python on Windows, simply download the installer for Python 3.9 from the official Python download page. If you're uncertain about which version to choose, it's best to opt for the Windows x86-64 executable installer. You can find it easily by following this link.

Make sure to select the “Add Python to PATH” option during installation to set Python 3.9 as the default version on your system. To verify the installation, you can use the command:

$ python --version

Python 3.9.0

Section 2: Upgrading Python on macOS

For macOS users, the upgrade process is similar to that of Windows. Download Python 3.9 from the Python download page. To check your current Python version, use the following commands:

$ python --version

Python 2.x.x

$ python3 --version

Python 3.9.0

If you'd prefer to run Python 3.9 using the python command instead of python3, you can set an alias in your .bash_profile located in your home directory. Open your terminal and execute:

$ cd $HOME

$ nano .bash_profile

Add this line at the end:

alias python="python3"

Now, you can run Python 3.9 simply by typing python:

$ python --version

Python 3.9.0

Section 3: Upgrading Python on Linux

For Linux users, you can install Python 3.9 by running the following commands:

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

$ sudo apt update

$ sudo apt install python3.9

To check the version of your newly installed Python, use:

$ sudo python --version

2.x.x

$ sudo python3 --version

3.8.x

$ sudo python3.9 --version

3.9.0