We recommend using Trinket to write Python online, as it has a number of advantages:
However, it may be that you are not able to use Trinket, especially if you are using computers without an Internet connection.
You can use this link to download version 3.2 of Python.
Installing Python will also install the IDLE Python editor, which is the simplest way of writing and running Python programs. IDLE consists of 2 windows, the editor (where programs are written) and the ‘Shell’ (where programs are run).
When IDLE is run, you will probably see the Python Shell window. You can open a new editor window by clicking ‘File → New Window’. Once you have written your program, you should save it (remembering to add .py to the end of your filename).