How can I set the focus to a widget (that isn't an entry) by clicking on it?

Question

The reason I need to do this is because I need to change the text of a label without having to use entries; I want to use events instead.

I have tried this:

import tkinter as tk

root = tk.Tk()
root.bind("<Button-1>", lambda _: root.focus())

l = tk.Label(root, width=50, height=50, bg="white")
l.bind("<Button-1>", lambda _: l.focus())
l.bind("1", lambda _: l.config(bg="yellow"))
l.bind("2", lambda _: l.config(bg="white"))
l.pack()

root.mainloop()

When I ran the program, I expected to be able to change the colour of the label l to yellow by clicking on it (which I thought would set the focus to it) then pressing 1, and changing it back to white by pressing 2; provided that I didn't click outside of the label and set the focus to the root widget (where the keys 1 and 2 weren't bound to any callback).

I know that you can bind keys to callbacks (tested it), and I also know that it is possible to set the focus to widgets which aren't entries (tested that too), yet this doesn't seem to work.

Can anybody help me?

Answer 1

The problem is that you have two bindings for a button click: one on the label widget itself and one on the root window. Because of the way that events are processed, the binding on the root window will fire after the event on the label. That means that whatever focus you set on the label binding will get undone with the binding on the root window.

One solution is to change your binding on the click to set the focus to whatever was clicked on. With that, you don't need to set a binding on the label widget for a click.

root.bind("<Button-1>", lambda event: event.widget.focus_set())

Another solution would be to modify your binding on the label to prevent the binding on the root window from firing. You can do that by returning the string "break" from the function that is called.

def callback(event):
    l.focus()
    return "break"
l.bind("<Button-1>", callback)