validation of tkinter entry widget

Question

I have an entry field in my tkinter GUI app. entry should only accept numbers including decimal points. I used a function to validate the entry. The problem is, it is not accepting decimal point(.) if there is a digit in front of it. (example 25.3 wont accept). if there is a point in the beginning, it is not accepting any number after that. Could anyone help me with this problem. and any suggestion to limit the maximum value in the entry field to 1000?

import tkinter as tk

def acceptNumber(inp):
    if inp.isdigit():
        return True
    elif inp is "":
        return True
    elif inp is ".":
        return True
    else:
        return False
win = tk.Tk()
reg = win.register(acceptNumber)

entryHere =tk.Entry(win)
entryHere.place(x=400, y=200)

entryHere.config(validate="key", validatecommand =(reg, '%P'))
win.mainloop()

Stef · Accepted Answer · 2019-07-16T10:26:00.020

1

This accepts valid decimal numbers not greater than 1000:

def acceptNumber(inp):
    try:
        return True if inp == '' else float(inp) <= 1000
    except:
        return False

edited Jul 16 '19 at 10:26

answered Jul 16 '19 at 10:15

Stef

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backspace won't work in this case to remove all digits. for example, if I typed 456, i wanna change into 786, backspace will remove only last two digits from 456 (ie. 4 will alwas be there) – master_yoda Jul 16 '19 at 10:19
if we can erase the data (using backspace in keyboard) , this is a good solution. – master_yoda Jul 16 '19 at 10:23
1

@sunny_old_days see updated version – Stef Jul 16 '19 at 10:26
Just rephrased it to look a bit nicer. – Stef Jul 16 '19 at 10:29

score 0 · Answer 2 · answered Jul 16 '19 at 10:18

0

>>> s='1234'
>>> s.isdigit()
True
>>> sdot = '1234.'
>>> sdot.isdigit()
False

Isn't this your problem. isdigit() means digits only.

answered Jul 16 '19 at 10:18

Mike O'Connor

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I used two elif statements as well ! – master_yoda Jul 16 '19 at 10:20

validation of tkinter entry widget

2 Answers2