from tkinter import *

def berechnen():
    wert1 = int(entry1.get())
    op    = entry2.get()
    wert2 = int(entry3.get())
    if op == '+':
        res = summe(wert1,wert2)
    elif op == '-':
        res = differenz(wert1,wert2)
    elif op == '*':
        res = produkt(wert1,wert2)
    elif op == '/':
        res = quotient(wert1,wert2)
    elif op == '**':
        res = potenz(wert1,wert2)
    label.config(text=str(res))
    

def summe(a,b):
      return a + b

def differenz(a,b):
      return a - b
          
def produkt(a,b):
      result = 0
      i = 0
      while i < b:
          result = summe(result,a)
          i +=1
      return result

def quotient(a,b):
      rest = a
      result = 0
      while rest >= b:
          rest = differenz(rest,b)
          result += 1
      return result

def potenz(a,b):
      if b == 0: return 1
      else:
        result = a
        i = 1
        while i < b:
          result = produkt(result,a)
          i +=1
        return result

fenster = Tk()
fenster.title('Rechner')
fenster.geometry('500x300')
fenster.resizable(0,0)
#fenster.iconbitmap('W:\symbol.ico')

label = Label(master=fenster,
              bg='lightgrey',
              fg='purple',
              text='Rechner',
              font=("Arial", 44))
label.place(x=10, y=200, width=230, height=50)

entry1 = Entry(master=fenster, bg='red', font=("Arial", 30))
entry1.place(x=10, y=70, width=120, height=50)

entry2 = Entry(master=fenster, bg='red', font=("Arial", 30))
entry2.place(x=140, y=70, width=50, height=50)

entry3 = Entry(master=fenster, bg='red', font=("Arial", 30))
entry3.place(x=200, y=70, width=120, height=50)

button = Button(master=fenster, bg='green', text='=', command=berechnen)
button.place(x=10, y=130, width=100, height=50)