Callback for tkinter Entry only executes once

Question

I want to have a function called, each time when an entry in my tkinter window is changed. Because I don't want the function to be called while the used is still typing, I chose "focusout" for the validate attribute. For clarification, I got the "focusout" idea from another thread, so I am not exactly sure what it does.

The function validate is called once, but never again. Why is that?

Minimum working example below:

 import tkinter as tk


 def validate():
     print("Checked!")


 root = tk.Tk()
 sv1 = tk.StringVar()
 sv2 = tk.StringVar()
 e1 = tk.Entry(root, textvariable=sv1, validate="focusout", validatecommand=validate)
 e2 = tk.Entry(root, textvariable=sv2, validate="focusout", validatecommand=validate)

 e1.pack()
 e2.pack()

 root.mainloop()

score 2 · Accepted Answer · answered Feb 03 '21 at 18:33

2

The validation function must return True or False, or it will be disabled.

answered Feb 03 '21 at 18:33

Bryan Oakley

370,779
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539
685

thanks, I just found a thread that answered it – Alex V. Feb 03 '21 at 18:36

score 1 · Answer 2 · answered Feb 03 '21 at 18:35

1

I finally found the answer. The validate function HAS TO RETURN True or False, or else it is turned off after one use.

See this thread: Interactively validating Entry widget content in tkinter

answered Feb 03 '21 at 18:35

Alex V.

180
2
12

Callback for tkinter Entry only executes once

2 Answers2