from Gui import *

def calculator():
    g = Gui()
    display = g.en(side=TOP, fill=NONE)
    g.gr(4, rweights=[1]*5, cweights=[1]*4, side=TOP)
    for key in ['7','8','9','+','4','5','6','-','1','2','3','*','0','.','E','/','(',')']:
        g.bu(text=key, command=Callable(display.insert, INSERT, key))
    def clear():
        display.delete(0, END)
    def evaluate():
        expression = display.get()
        clear()
        display.insert(INSERT, eval(expression))
    g.bu(text='C', command=clear)
    g.bu(text='=', command=evaluate)
    g.endgr()
    g.mainloop()