There are several ways to build GUIs in Maya. In this book, we will take the approach described in this section. While this is not the only approach one can take, I certainly think it is the most productive in both the short and long term. Once you are able to execute on the concepts in this chapter, you will want to use them for all your user interfaces. In my experience, the approach presented here has proved valuable time and time again.
Build your GUIs in pure Python, runnable completely outside of Maya. Then from inside of Maya, connect to signals that are emitted from your GUI. Likewise, the GUI can connect through an intermediary to signals that are emitted from Maya. By doing this, your GUIs will be more abstract (they will not contain Maya code) and much faster to develop (you do not need to build them in Maya or run Maya to test them).
There are exceptions to this rule that are covered in the second rule...