I have used a lot of differnet text editors and IDE's over the time. It has all come down to me only using two tools/editors/IDE's for my development.
I don't see any need for code completion when programming in Python. It's a basic language and it will only benefit you to type all of the code on your own. The only persons I recommend to use tools with code completion is experienced programmers since they already know the syntax and knows how to write the code.
When dealing with Python you can either use IDLE which comes with Python or in my opinion the best text editor out there Sublime Text editor. IDLE comes with Python and is really simple to use I wouldn't choose it though because of a of features which decreases the workflow.
For general programming I use Sublime text editor. The reason for me to choose this is the simplicity. It's very fast and have a very clean interface. It has code highlightning for almost every programming language. There is no need to buy it unless you want to support the developers. The only difference between the paid version and the free one is a pop up box asking for you to buy it once in an hour or so. http://www.sublimetext.com/