With the terminal, the text editor is a developer's most important tool. Everyone has their preferences, but unless you're a hardcore Vim) user, a lot of people are going to tell you that Sublime Text is currently the best one out there.
Go ahead and download it. Open the .dmg file, drag-and-drop in the Applications folder, you know the drill now. Launch the application.
Note: At this point I'm going to create a shorcut on the OS X Dock for both for Sublime Text and iTerm. To do so, right-click on the running application and select Options > Keep in Dock.
Sublime Text is not free, but it has an unlimited "evaluation period". Anyhow, we're going to be using it so much that even the seemingly expensive $60 price tag is worth every penny. If you can afford it, It is adviced that you support this awesome tool. :)
Let's create a shortcut so we can launch Sublime Text from the command-line:
$ ln -s /Applications/Sublime\ Text.app/Contents/SharedSupport/bin/subl /usr/local/bin/subl
Now you can open a file with $ subl myfile.py or start a new project in the current directory with $ subl .. Pretty cool. We'll configure Sublime more in the next few sections.