[Tkinter] How to restrict characters used in an Entry widget?

[woooee]

200+ lines of code for one simple call is more than I want to go through, so this is a simple example of using trace to validate code/

try:
    import Tkinter as tk     ## Python 2.x
    import ttk
except ImportError:
    import tkinter as tk     ## Python 3.x
    from tkinter import ttk

class Converter:
    def __init__(self, top):
        self.vars = tk.StringVar()
        self.vars.trace('w', self.validate)
        self.Entry1 = tk.Entry(top, textvariable = self.vars,
                               width=20).grid()

    def validate(self, *args):
        if not self.vars.get().isalpha():
            corrected = ''.join(filter(str.isalpha, self.vars.get()))
            self.vars.set(corrected)
 
root=tk.Tk()
C=Converter(root)
root.mainloop()