from tkinter import*

def iCalc(source, side):
    storeObj = Frame(source,borderwidth = 1, bd= 4,bg="powder blue")
    storeObj.pack(side=side,expand=YES,fill=BOTH)
    return storeObj

def button (source, side, text, command=None):
    storeObj = Button(source, text=text, command=command)
    storeObj.pack(side=side,expand=YES,fill=BOTH)
    return storeObj

class app(Frame):
    def __init__(self):
        Frame.__init__(self)
        self.option_add('*Font','arial 20 bold')
        self.pack(expand=YES,fill=BOTH)
        self.master.title('Calculator')

        display = StringVar()
        Entry(self,relief= RIDGE, textvariable=display,justify='right',bd=30,bg="powder blue").pack(side=Top,expand=YES,fill=BOTH)

        for clearBut in (["CE"],["C"]):
            erase = iCalc(self,TOP)
            for ichar in clearBut:
                button(erase,LEFT,ichar,
                       lambda storeObj=display, q=ichar: storeObj.set(''))

        for NumBut in ("789/","456*","123-","0.+"):
            FunctionNum = iCalc(self,TOP)
            for iEquals in NumBut:
                button(FunctionNum,LEFT,iEquals,
                       lambda storeObj=display,q=char: storeObj.set(storeObj.get() +q))

        EqualsButton = iCalc(self,TOP)
        for iEquals in "=":
            if iEquals == '=':
                btniEquals = button(EqualsButton,LEFT,iEquals)
                btniEquals.bind('<ButtonRelease-1>',
                                lambda e, s=self, storeObj=display: s.calc(storeObj), '+')
            else:
                btniEquals = button(EqualsButton,LEFT,iEquals,
                                    lambda storeObj=display,s=' %s '%iEquals:storeObj.set(storeObj.set(storeObj.get()+s))
                                    

    def calc(self, display):
        try:
            display.set(eval(display.get()))
        except:
            display.set("ERROR")

if __name__=='__main__':
    app().mainloop()