Restricting the value in Tkinter Entry widget

Question

I need to restrict the values in the Entry widget to numbers only. The way I implemented is:

import numpy as np
from Tkinter import *;
import tkMessageBox;

         


        

Answer 1

I had to deal with an initial insert case as well. This is what I have ended up with:

    def _checkNumberOnly(self, action, value_if_allowed):
        if action != '1':
           return True
        try:
            return value_if_allowed.isnumeric()
        except ValueError:
           return False

    vcmd = (self.register(self._checkNumberOnly), '%d', '%P')
        self.port = ttk.Entry(self, width=35, validate='key', validatecommand=vcmd)

Therefore it validates for the following:

    self.port.insert(0, '6379')

I'm not sure that the catch is needed, due to isnumeric() not stating it raises an exception.