Калькулятор. Just for fun

#!/usr/bin/python

# calculator.py

import wx

class Calc:
    def __init__(self):
        self.formula = ""
        self.text = ""
        self.clearText = False
       
    def Add(self, char):
       
        if char.isdigit() or char == '.':
            if self.clearText:
                self.text = char
            else:
                self.text = self.text + char
            self.formula = self.formula + char
            self.clearText = False
           
        elif char == "Cls":
            self.text = self.formula = ""
           
        elif char == "Bck":
            if len(self.formula) and self.formula[-1].isdigit():
                self.formula = self.formula[:-1]
                self.text = self.text[:-1]
       
        elif char == "=":
            try:
                self.formula = self.text = str(eval(self.formula))
            except StandardError:
                self.text = "Error"
                self.formula = ''
            self.clearText = True
        else:
            self.formula = self.formula + char
            self.clearText = True
           
    def Get(self):
        return self.text
   

class MyFrame(wx.Frame):
    def __init__(self, parent, id, title):

        wx.Frame.__init__(self, parent, id, title, wx.DefaultPosition, wx.Size(300, 250))
       
        self.calc = Calc()
       
        sizer = wx.BoxSizer(wx.VERTICAL)
        self.display = wx.TextCtrl(self, -1, '',  style=wx.TE_RIGHT | wx.TE_READONLY )
        sizer.Add(self.display, 0, wx.EXPAND | wx.TOP | wx.BOTTOM, 4)

        gs = wx.GridSizer(4, 4, 3, 3)
       
        bNumbers = [(wx.Button(self, wx.NewId(), "%i" %i), 0, wx.EXPAND) for i in xrange(10)]

        bExeTexts = ["Cls", "Bck", "="]
        bExes = [(wx.Button(self, wx.NewId(), bExeTexts), 0, wx.EXPAND) for i in xrange(3)]

        bOperTexts = ["/", "*", "-", "+", "."]
        bOpers = [(wx.Button(self, wx.NewId(), bOperTexts), 0, wx.EXPAND) for i in xrange(5)]

        buttons = bExes + [(wx.Size(10, 10), 0, wx.EXPAND)] + bNumbers + bOpers

        gs.AddMany(buttons)
       
        sizer.Add(gs, 1, wx.EXPAND)

        self.SetSizer(sizer)
        self.Centre()
       
        self.Bind(wx.EVT_BUTTON, self.OnButton)
       
    def OnButton(self, event):
        self.calc.Add(self.FindWindowById(event.GetId()).GetLabel())
        self.display.ChangeValue(self.calc.Get())
       
       
class MyApp(wx.App):
    def OnInit(self):
        frame = MyFrame(None, -1, 'calculator.py')
        frame.Show(True)
        self.SetTopWindow(frame)
        return True

def main():
    app = MyApp(redirect = False)
    app.MainLoop()

if __name__ == "__main__":
    main()