Emacs is a very popular text editor for coding. It has been around since the mid 1970s and is still being actively developed. It is our choice of editor. It has a lot of key-bindings (Key combinations that usually involve the ctrl or alt keys), and you can use it completely without touching a mouse. It takes a bit of an effort to get used to the key-bindings, but once you do, your productivity increases a lot. If you are not familiar with any coding text editor, we strongly suggest learning how to use Emacs. To do that, you can follow Absolute Beginner's Guide to Emacs. Make a cheat sheet of the main key-bindings (moving around, copying, pasting, undo, etc.). You can go through this in thirty minutes to one hour. Try to use Emacs at every chance you get, especially as you go through the next steps of prework that involves coding. The Python tutorial and coding exercises of Think Stats provide excellent chances to do so. This will give you experience and get you faster.
Sublime Text text is another popular editor, but it's not free. Vim has been around as long as Emacs has, and shares the full-keyboard input philosophy, but is arguably harder to learn for a beginner. If you are already familiar with one of these or a different text editor that highlights code syntax, you are welcome to use that.