from tkinter import *
def resize(ev=None):
    label.config(font='Helvica  -%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, bg= 'white', fg= 'red')
quit.pack(fill=X, expand= 1)

mainloop()	
