from tkinter import*
I=IntVar
B=Checkbutton
class f(Tk):
    def __init__(self):
        s=self
        Tk.__init__(s)
        s.c=I()
        s.v=I()
        s.C=B(self,text="FAST",variable=s.c,onvalue=1,offvalue=0)
        s.C.pack()
        s.cs=0
        Tk.after(s,100,f)
    def f(self):
        s=self
        if s.c != s.cs:
            print(s.c)
            s.cs=s.c
        Tk.after(s,100,f)
f().mainloop()