import Tkinter,tkFont

window=Tkinter.Tk()
canvas=Tkinter.Canvas(window)
canvas.pack()

m={}
i=-1
while 1:
    i+=1
    font=("Times",(i%30)+10,"bold")
    font_obj=tkFont.Font(font=font)
    name=str(font_obj)
    if m.has_key(name):
        print "previously:",m[name]
        print "now:",font
        print "iterations:",i
        print "mapping:",m
        assert 0
    else:
        m[name]=font
    canvas.create_text((50,i), text="foobar", font=font_obj)

window.mainloop()