from Tkinter import *
def resize(ev=None):
label.config(font='Helvetica -%d bold' % scale.get())
top = Tk()
top.geometry('250x150')
label = Label(top, text='Hello World!',font='Helvetica -12 bold')
label.pack(fill=Y, expand=1)
scale = Scale(top, from_=10, to=40,orient=HORIZONTAL, command=resize)
scale.set(12)
scale.pack(fill=X, expand=1)
quit = Button(top, text='QUIT',command=top.quit, activeforeground='white',activebackground='red')
quit.pack()
mainloop()