from Tkinter import *

class MyClass:
    def __init__(self, parent):
        self.myParent = parent
        self.portVar = IntVar()
        self.portVar.set(111)

        port_validator = self.myParent.register(self._validate)

        self.myEntry = Entry(self.myParent, width=9, textvariable=self.portVar,
            validate='all', validatecommand=(port_validator,'%d', '%i', '%P', '%s', '%S', '%v', '%V', '%W'))

        self.myEntry.pack(side=TOP)


    def _validate(self, d, i, P, s, S, v, V, W):
        print "OnValidate: d='%s' i='%s' P='%s' s='%s' S='%s' v='%s' V='%s' W='%s'" % (d, i, P, s, S, v, V, W)
        return P.isdigit()


root = Tk()
myclass = MyClass(root)
root.mainloop()