There are many different libraries for GUI (graphical user interfaces), many of them with Python bindings: PyGTK, PyQt, PySide, etc. Tkinter is one of the oldest Python GUI libraries and is considered to be the standard one. Another popular choice is wxPython, a Python interface for wxWidgets C++ library.
A quick example of wxPython is provided in wxvpconvert, a silly GUI for Madagascar’s vpconvert script. Compare with tkvpconvert.