calc.py

import math
import tkinter as tk


def startCalc():
    def clk(key):
        global memory
        if key == '=':
            if('/' in entry.get() and '.' not in entry.get()):
                entry.insert(tk.END, ".0")
            str1 = "-+0123456789."
            if(entry.get()[0] not in str1):
                entry.insert(tk.END, "first char not in " + str1)
            try:
                result = eval(entry.get())
                entry.insert(tk.END, " = " + str(result))
            except:
                entry.insert(tk.END, "--> Error!")
        elif(key == 'C'):
            entry.delete(0, tk.END)
        elif(key == '->M'):
            memory = entry.get()
            if('=' in memory):
                ix = memory.find('=')
                memory = memory[ix+2:]
            root.title('M=' + memory)
        elif(key == 'M->'):
            entry.insert(tk.END, memory)
        elif(key == 'neg'):
            if('=' in entry.get()):
                entry.delete(0, tk.END)
            try:
                if(entry.get()[0] == '-'):
                    entry.delete(0)
                else:
                    entry.insert(0, '-')
            except IndexError:
                pass
        else:
            if('=' in entry.get()):
                entry.delete(0, tk.END)
            entry.insert(tk.END, key)


    root = tk.Tk()
    root.title("Calculator")
    buttons = [
        '7',  '8',  '9',  '*',  'C',
        '4',  '5',  '6',  '/',  'M->',
        '1',  '2',  '3',  '-',  '->M',
        '0',  '.',  '=',  '+',  'neg']

    r = 1
    c = 0
    for b in buttons:
        cmd = lambda x = b: clk(x)
        tk.Button(root, text = b, width = 5, relief = "ridge", command = cmd).grid(row = r, column = c)
        c += 1
        if c > 4:
            c = 0
            r += 1
    entry = tk.Entry(root, width = 33, bg = "white")
    entry.grid(row = 0, column = 0, columnspan = 5)
    root.iconbitmap('icon.ico')
    root.mainloop()