I use PyGTK and gtk.Builder for my application. I want to be able to call connect_signals multiple times, because I created a class for every dialog, in which I want the signal handlers to be placed. 
I looked at the original C code, but I did not understand it completely (that's why I'm using PyGTK). So I don't know whether this is possible or not.

Example code:
import gtk

class FirstWindow:
    def __init__(self, builder):
        builder.connect_signals(self)
    
    def on_button1_clicked(self, widget, data=None):
        print "Button 1 clicked."

class SecondWindow:
    def __init__(self, builder):
        builder.connect_signals(self)
        
    def on_button2_clicked(self, widget, data=None):
        print "Button 2 clicked."
    

builder = gtk.Builder()
builder.add_from_file("ui.xml")

firstwindow = FirstWindow(builder)
secondwindow = SecondWindow(builder)
builder.get_object("firstwindow").show()
builder.get_object("secondwindow").show()
gtk.main()
# When clicking each button once, the output is:
# >> Button 1 clicked