GUI_Additional.py

from Tkinter import *

class ValidatingEntry(Entry):
    # base class for validating entry widgets

    def __init__(self, master, value="", **kw):
        apply(Entry.__init__, (self, master), kw)
        self.__value = value
        self.__variable = StringVar()
        self.__variable.set(value)
        self.__variable.trace("w", self.__callback)
        self.config(textvariable=self.__variable)

    def __callback(self, *dummy):
        value = self.__variable.get()
        newvalue = self.validate(value)
        if newvalue is None:
            self.__variable.set(self.__value)
        elif newvalue != value:
            self.__value = newvalue
            self.__variable.set(self.newvalue)
        else:
            self.__value = value

    def validate(self, value):
        # override: return value, new value, or None if invalid
        return value

class IntegerEntry(ValidatingEntry):

    def validate(self, value):
        try:
            if value:
                v = int(value)
            return value
        except ValueError:
            return None

class FloatEntry(ValidatingEntry):

    def validate(self, value):
        try:
            if value:
                v = float(value)
            return value
        except ValueError:
            return None