import wx

class MyFrame(wx.Frame):
    def __init__(self, parent, id, title):
    
        wx.Frame.__init__(self, parent, id, title, wx.DefaultPosition, wx.Size(300, 250))
        self.formula = False
        
        menubar = wx.MenuBar()

        file = wx.Menu()
    
        file.Append(22, '&Quit', 'Exit Calculator')
    
        menubar.Append(file, '&file')
    
        self.SetMenuBar(menubar)
    
        wx.EVT_MENU(self, 22, self.OnClose)
       
        sizer = wx.BoxSizer(wx.VERTICAL)
        self.display = wx.TextCtrl(self, -1, '', style = wx.TE_RIGHT)
        sizer.Add(self.display, 0, wx.EXPAND|wx.TOP|wx.BOTTOM, 4)
        
    
        gs = wx.GridSizer(5, 4, 5, 5)
    
        gs.AddMany([(wx.Button(self, 20, 'Cls'), 0, wx.EXPAND),
                    (wx.Button(self, 21, 'Bck'), 0, wx.EXPAND),
                    (wx.StaticText(self, -1, ''), 0, wx.EXPAND),
                    (wx.Button(self, 22, 'Close'), 0, wx.EXPAND),
                    (wx.Button(self, 1, '7'), 0, wx.EXPAND),
                    (wx.Button(self, 2, '8'), 0, wx.EXPAND),
                    (wx.Button(self, 3, '9'), 0, wx.EXPAND),
                    (wx.Button(self, 4, '/'), 0, wx.EXPAND),
                    (wx.Button(self, 5, '4'), 0, wx.EXPAND),
                    (wx.Button(self, 6, '5'), 0, wx.EXPAND),
                    (wx.Button(self, 7, '6'), 0, wx.EXPAND),
                    (wx.Button(self, 8, '*'), 0, wx.EXPAND),
                    (wx.Button(self, 9, '1'), 0, wx.EXPAND),
                    (wx.Button(self, 10, '2'), 0, wx.EXPAND),
                    (wx.Button(self, 11, '3'), 0, wx.EXPAND),
                    (wx.Button(self, 12, '-'), 0, wx.EXPAND),
                    (wx.Button(self, 13, '0'), 0, wx.EXPAND),
                    (wx.Button(self, 14, '.'), 0, wx.EXPAND),
                    (wx.Button(self, 15, '='), 0, wx.EXPAND),
                    (wx.Button(self, 16, '+'), 0, wx.EXPAND)])
        
        sizer.Add(gs, 1, wx.EXPAND)
        
        self.SetSizer(sizer)
        self.Centre()
        
        self.Bind(wx.EVT_BUTTON, self.OnClear, id=20)
        self.Bind(wx.EVT_BUTTON, self.OnBackspace, id=21)
        self.Bind(wx.EVT_BUTTON, self.OnClose, id=22)
        self.Bind(wx.EVT_BUTTON, self.OnSeven, id=1)
        self.Bind(wx.EVT_BUTTON, self.OnEight, id=2)
        self.Bind(wx.EVT_BUTTON, self.OnNine, id=3)
        self.Bind(wx.EVT_BUTTON, self.OnDivide, id=4)
        self.Bind(wx.EVT_BUTTON, self.OnFour, id=5)
        self.Bind(wx.EVT_BUTTON, self.OnFive, id=6)
        self.Bind(wx.EVT_BUTTON, self.OnSix, id=7)
        self.Bind(wx.EVT_BUTTON, self.OnMultiply, id=8)
        self.Bind(wx.EVT_BUTTON, self.OnOne, id=9)
        self.Bind(wx.EVT_BUTTON, self.OnTwo, id=10)
        self.Bind(wx.EVT_BUTTON, self.OnThree, id=11)
        self.Bind(wx.EVT_BUTTON, self.OnMinus, id=12)
        self.Bind(wx.EVT_BUTTON, self.OnZero, id=13)
        self.Bind(wx.EVT_BUTTON, self.OnDot, id=14)
        self.Bind(wx.EVT_BUTTON, self.OnEqual, id=15)
        self.Bind(wx.EVT_BUTTON, self.OnPlus, id=16)
        

    def OnClear(self, event):
        self.display.Clear()
        
    def OnBackspace(self, event):
        formula = self.display.GetValue()
        self.display.Clear()
        self.display.SetValue(formula[:-1])
        
    def OnClose(self, event):
        self.Close()
        
    def OnDivide(self, event):
        if self.formula:
            return
        self.display.AppendText('/')
        
    def OnMultiply(self, event):
        if self.formula:
            return
        self.display.AppendText('*')    
        
    def OnMinus(self, event):
        if self.formula:
            return
        self.display.AppendText('-')
        
    def OnPlus(self, event):
        if self.formula:
            return
        self.display.AppendText('+')
        
    def OnDot(self, event):
        if self.formula:
            return
        self.display.AppendText('.')
        
    def OnEqual(self, event):
        if self.formula:
            return
        formula = self.display.GetValue()
        self.formula = False
        
        try:
            self.display.Clear()
            output = eval(formula)
            self.display.AppendText(str(output))
        except StandardError:
            self.display.AppendText("Error")
        
        
    def OnZero(self, event):
        if self.formula:
            self.display.Clear()
            self.formula = False
        self.display.AppendText('0')
        
    def OnOne(self, event):
        if self.formula:
            self.display.Clear()
            self.formula = False
        self.display.AppendText('1')
        
    def OnTwo(self, event):
        if self.formula:
            self.display.Clear()
            self.formula = False
        self.display.AppendText('2')
        
    def OnThree(self, event):
        if self.formula:
            self.display.Clear()
            self.formula = False
        self.display.AppendText('3')
        
    def OnFour(self, event):
        if self.formula:
            self.display.Clear()
            self.formula = False
        self.display.AppendText('4')
        
    def OnFive(self, event):
        if self.formula:
            self.display.Clear()
            self.formula = False
        self.display.AppendText('5')
        
    def OnSix(self, event):
        if self.formula:
            self.display.Clear()
            self.formula = False
        self.display.AppendText('6')
        
    def OnSeven(self, event):
        if self.formula:
            self.display.Clear()
            self.formula = False
        self.display.AppendText('7')
        
    def OnEight(self, event):
        if self.formula:
            self.display.Clear()
            self.formula = False
        self.display.AppendText('8')
        
    def OnNine(self, event):
        if self.formula:
            self.display.Clear()
            self.formula = False
        self.display.AppendText('9')
        
class MyApp(wx.App):
    def OnInit(self):
        frame = MyFrame(None, -1, 'Calculator.py')
        frame.Show(True)
        return True
    
app = wx.App()
mainapp = MyApp(app)
mainapp.MainLoop()