wxGlade is a GUI designer written in Python with the popular GUI toolkit wxPython which helps create wxWidgets/wxPython user interfaces. It is not a full featured IDE, but simply a "designer": the generated code does nothing apart from displaying the created widgets.
While not related to Glade Interface Designer for GTK+, they are similar in idea and interface. As such they have comparable possibilities, and a user knowing one can quickly learn the other. Output files are not directly interchangeable because the used XML dialects differs.