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

The answer is almost perfect, just a little addition to allow for deleting the whole string. The check for floats should be done only when inserting text

def validate_float(self, action, index, value_if_allowed,
    prior_value, text, validation_type, trigger_type, widget_name):
    # action=1 -> insert
    if(action=='1'):
        if text in '0123456789.-+':
            try:
                float(value_if_allowed)
                return True
            except ValueError:
                return False
        else:
            return False
    else:
        return True