from Tkinter import *
#Global variable 'count' stores the number of button clicks
count = 0

def button_pressed_cb(root):
    global count
    count += 1
    print "Hello again - the button was pressed: ", count, " time(s)."

root=Tk()


button = Button(root,text='Count',command=lambda:button_pressed_cb(root))
button.pack()
root.mainloop()