Difficulty: Moderately Easy
Look at Editors
Step1
Search Open Source indexing sites for a list of text editors available for your platform. There are a wide variety of editors suitable for various platforms. These text editors provide comfortable editing for beginners and advanced users alike, though some are geared more toward one end or the other of the spectrum.
Step2
Investigate the 2 most popular editors: Vim and Emacs. These are extremely powerful editors for more advanced users, but beginners can use the more basic features until they've learned a little more Python programming.
Step3
Look at simpler editors. If Vim and Emacs are too complex for you, there are many simpler editors from which to choose. The minimum features you'll need for Python programs are indentation and syntax highlighting.
Step4
Narrow your choices. Choose an editor that has the features you will use the most and not many more extemporaneous features. Choosing an editor with a large number of features you'll never use will just make your environment more confusing and won't add to your Python programs in any way.
Look at IDEs
Step1
Decide whether an IDE is a better choice for you. An IDE provides many more language-specific features such as project management and code refactoring than does a simple editor.
Step2
Look at the list of Python IDEs available on the Python wiki (see Resources below). While not all of these are strictly Python IDEs, they all have Python editing capabilities in addition to features for compiling, interpreting, building and, possibly, debugging your code.
Step3
Narrow the list and choose an IDE that will not only run on your platform, but is regularly maintained and is in your price range.
Step4
Download and try out the IDE. The best way to see if you like an IDE is to install it and try it. If you don't like it, you can always uninstall it later and choose a new one.