num1 = "" operator = "" 1 2 3 + 4 5 6 - 7 8 9 = 0 C def number(n): global num1 num1 += str(n) display.text = num1 def set_operator(op): global num1, operator if operator != "" or num1 == "": return operator = op num1 += op display.text = num1 def calculate(): global num1, operator if operator == "": return parts = num1.split(operator) if len(parts) != 2 or parts[0] == "" or parts[1] == "": return a = int(parts[0]) b = int(parts[1]) result = a + b if operator == "+" else a - b display.text = str(result) num1 = str(result) operator = "" def clear(): global num1, operator num1 = "" operator = "" display.text = "0" btn1.on("click", lambda e: number(1)) btn2.on("click", lambda e: number(2)) btn3.on("click", lambda e: number(3)) btn5.on("click", lambda e: number(4)) btn6.on("click", lambda e: number(5)) btn7.on("click", lambda e: number(6)) btn9.on("click", lambda e: number(7)) btn10.on("click", lambda e: number(8)) btn11.on("click", lambda e: number(9)) btn13.on("click", lambda e: number(0)) btn4.on("click", lambda e: set_operator("+")) btn8.on("click", lambda e: set_operator("-")) btn12.on("click", lambda e: calculate()) btn14.on("click", lambda e: clear())