Bug report

Bug description:

If you run de following code:

import tkinter as tk

class Label2(tk.Label):
     def __init__(self, top, text):
         tk.Label.__init__(self, top, text=text, bg='Yellow')

w = tk.Tk()
w.columnconfigure((0, 1, 2), weight=1, uniform='u1')

label_1 = tk.Label(w, text='Native Label\nInstance 1', bg='LightGreen')
label_1.grid(column=0, row=0)
label_2 = Label2(w, text='Label2 Label\nInstance 1')
label_2.grid(column=1, row=0)
label_3 = tk.Label(w, text='Native Label\nInstance 2', bg='LightGreen')
label_3.grid(column=2, row=0)
w.mainloop()

It will produce the following result (only label_1 and label_3 seems to be placed) :

instead of what you expect (the following result) :

Note: This code is using Label for simplicity but it's the same with other widgets !

Explanation:
This is because of automatic generated tkinter widget names:
label_1 name is '.!label'
label_2 name is '.!label2'
label_3 name is '.!label2'

So 'label_2' and 'label_3' has the same widget name.
If you print the 'w.winfo_children()' function just before the 'w.mainloop()', you just get 2 widgets in the list.
The 'label_3' override the 'label_2' because for tkinter they are the same !

To get around this bug:

• you should not name your class by simply adding a number (like '2' or '3' ...)
• or you must give a unique name of your class instance with the 'name=' option in the Label constructor.

To correct the bug:
The naming algorithm should check that the automatically generated name is not already in use.

CPython versions tested on:

3.9, 3.13

Operating systems tested on:

Linux, Windows

Linked PRs

• gh-128562: Fix tkinter widget instance name sometimes duplicated on inherited class #128604
• [3.13] gh-128562: Fix generation of the tkinter widget names (GH-128604) #128791
• [3.12] gh-128562: Fix generation of the tkinter widget names (GH-128604) #128792