The Python 2.7 PyQt4 toolsets are quite complete. WinPython 2.7 comes with QtDesigner and MatplotlibWidget out of the box. This project is a good starting point for a data visualization project for these platforms.

• in UI designer add a MatplotlibWidget and save as ui_main.ui
• run ui2py.py to convert ui_main.ui -> ui_main.py
• create a file like run.py and at the top import the ui with import ui_main
• write some code to interact with the UI (look at the source code for details)
• key lines for transparent matplotlib window (with transparent background and transparent frame):

self.matplotlibwidget.axes.set_axis_bgcolor('none') # make a transparent graph background
self.matplotlibwidget.figure.set_facecolor('none') # make a transparent frame background