1 #!/usr/bin/env python
   2 # -*- coding: cp1252 -*-
   3 """
   4 Calculadora com GUI em Tkinter, utilizando funções internas do Python
   5 Baseada na implementação de Mark Lutz em "Programming Python", pág. 675
   6 
   7 Autor deste script: Jean-Guy Schneider <schneidr@iam.unibe.ch>
   8 Última modificação Mon Jun 22 17:36:02 MET DST 1998
   9 """
  10 from Tkinter import *
  11 
  12 class CalcGUI (Frame):
  13     """
  14     class 'CalcGUI': a simple calculator
  15     """
  16     
  17     def __init__ (self, master=None):
  18         Frame.__init__ (self, master)
  19         self.pack (expand=YES, fill=BOTH)
  20         self.master.title ('Python Calculator')
  21         self.master.iconname ("pcalc")
  22 
  23         self._names = {}                  # private namespace for expressions
  24 
  25         self._text = Text (self, width=16, height=1)     # a text widget
  26         self._text.pack (expand=YES, fill=X)             # as display
  27 
  28         rows = ["abcd", "0123", "4567", "89()"]          # buttons
  29         for row in rows:
  30             frm = Frame (self)                           # into separate frame
  31             for char in row:
  32                 but = Button (frm, text=char,
  33                               command=lambda s=self, y=char: s._append (y))
  34                 but.pack (side=LEFT, expand=YES, fill=X)
  35             frm.pack (expand=YES, fill=X)
  36 
  37         frm2 = Frame (self)
  38         for char in "+-*/=":                             # operators
  39             but = Button (frm2, text=char,
  40                           command=lambda s=self, y=char: s._append (' '+y+' '))
  41             but.pack (side=LEFT, expand=YES, fill=X)
  42         frm2.pack (expand=YES, fill=X)
  43 
  44         frm3 = Frame (self)                               # command buttons
  45         but = Button (frm3, text='eval', command=lambda s=self: s.eval ())
  46         but.pack (side=LEFT, expand=YES, fill=X)
  47         but = Button (frm3, text='clear', command=lambda s=self: s._clear ())
  48         but.pack (side=LEFT, expand=YES, fill=X)
  49         but = Button (frm3, text='exit', command=self.quit)
  50         but.pack (side=LEFT, expand=YES, fill=X)
  51         frm3.pack (expand=YES, fill=X)
  52 
  53     def eval (self):
  54         try:
  55             cont = self._get()                           # get contents
  56             self._clear()                                # clear text widget
  57                                                          # eval as expression
  58             self._append (`eval (cont, self._names, self._names)`)
  59         except SyntaxError:
  60             try:
  61                 exec (cont, self._names, self._names)    # exec as statement
  62             except:
  63                 self._append ("ERROR")
  64             else:
  65                 self._clear()                            # worked as statement
  66         except:
  67             self._append ("ERROR")                       # other errors
  68 
  69     # private helper functions: text widget manipulation
  70     def _clear (self):
  71         """Clear text widget"""
  72         self._text.delete ('1.0', '2.0')
  73 
  74     def _append (self, text):
  75         """Append 'text' to text widget"""
  76         self._text.insert ('1.end', text)
  77 
  78     def _get (self):
  79         """get contents of text widget"""
  80         return self._text.get ('1.0', '1.end')
  81 
  82 if __name__ == '__main__':
  83     CalcGUI().mainloop()