guicalc.py

# guicalc.py - a Python calculator
from Tkinter import *

# the main class
class Calc():
    def __init__(self):
        self.total = 0
        self.current = ""
        self.new_num = True
        self.op_pending = False
        self.op = ""
        self.eq_flag = False

    def num_press(self, num):
        temp = text_box.get()
        self.eq_flag = False
        temp2 = str(num)
        if self.new_num == True:
            self.current = temp2
            self.new_num = False
        else:
            if temp2 == '.':
                if temp2 in temp:
                    return
            self.current = temp + temp2
        text_box.delete(0, END)
        text_box.insert(0, self.current)

    def calc_total(self):
        if self.op_pending == True:
            self.do_sum()
            self.op_pending = False

    def do_sum(self):
        self.current = float(self.current)
        if self.op == "add":
            self.total += self.current
        if self.op == "minus":
            self.total -= self.current
        if self.op == "times":
            self.total *= self.current
        if self.op == "divide":
            self.total /= self.current
        text_box.delete(0, END)
        text_box.insert(0, self.total)
        self.new_num = True

    def operation(self, op):
        if self.op_pending == True:
            self.do_sum()
            self.op = op
        else:
            self.op_pending = True
            if self.eq_flag == False:
                self.total = float(text_box.get())
            else:
                self.total = self.current
            self.new_num = True
            self.op = op
            self.eq_flag = False

    def cancel(self):
        text_box.delete(0, END)
        text_box.insert(0, "0")
        self.new_num = True

    def all_cancel(self):
        self.cancel()
        self.total = 0

    def sign(self):
        self.current = -(float(text_box.get()))
        text_box.delete(0, END)
        text_box.insert(0, self.current)

class My_Btn(Button):
    def btn_cmd(self, num):
        self["command"] = lambda: sum1.num_press(num)

sum1 = Calc()
root = Tk()
calc = Frame(root)
calc.grid()

root.title("Calculator")
text_box = Entry(calc, justify=RIGHT)
text_box.grid(row = 0, column = 0, columnspan = 3, pady = 5)
text_box.insert(0, "0")

# make the buttons
numbers = "789456123"
i = 0
bttn = []
for j in range(1,4):
    for k in range(3):
        bttn.append(My_Btn(calc, text = numbers[i]))
        bttn[i].grid(row = j, column = k, pady = 5)
        bttn[i].btn_cmd(numbers[i])
        i += 1
bttn_0 = Button(calc, text = "0")
bttn_0["command"] = lambda: sum1.num_press(0)
bttn_0.grid(row = 4, column = 1, pady = 5)

bttn_div = Button(calc, text = chr(247))
bttn_div["command"] = lambda: sum1.operation("divide")
bttn_div.grid(row = 1, column = 3, pady = 5)

bttn_mult = Button(calc, text = "x")
bttn_mult["command"] = lambda: sum1.operation("times")
bttn_mult.grid(row = 2, column = 3, pady = 5)

minus = Button(calc, text = "-")
minus["command"] = lambda: sum1.operation("minus")
minus.grid(row = 3, column = 3, pady = 5)

point = Button(calc, text = ".")
point["command"] = lambda: sum1.num_press(".")
point.grid(row = 4, column = 0, pady = 5)

add = Button(calc, text = "+")
add["command"] = lambda: sum1.operation("add")
add.grid(row = 4, column = 3, pady = 5)

neg= Button(calc, text = "+/-")
neg["command"] = sum1.sign
neg.grid(row = 5, column = 0, pady = 5)

clear = Button(calc, text = "C")
clear["command"] = sum1.cancel
clear.grid(row = 5, column = 1, pady = 5)

all_clear = Button(calc, text = "AC")
all_clear["command"] = sum1.all_cancel
all_clear.grid(row = 5, column = 2, pady = 5)

equals = Button(calc, text = "=")
equals["command"] = sum1.calc_total
equals.grid(row = 5, column = 3, pady = 5)

root.mainloop()