Tkinter update label text in callback

Question

Salutations, I've tried to find a problem that is similar to mine, but haven't managed. I am trying to update a ttk Label from the callback function that runs when changing the content of a ttk Entry. I tried to isolate the issue here:

import tkinter
from tkinter import ttk


def func():
    print("func!")
    lsv.set("CHANGED!")


# def func2():
#    return


root = tkinter.Tk()

frame = ttk.Frame(root)
frame.pack()

sv = tkinter.StringVar()
sv.trace_add("write", lambda *args: func())

entry = ttk.Entry(frame, textvariable=sv, width=25)
entry.pack()


lsv = tkinter.StringVar()
lsv.trace_add("read", ????). # lambda *args: func2() ?
lsv.set("Hello World")

label = ttk.Label(frame, text=lsv.get())
label.pack()

root.mainloop()

With this code, I manage to print out "func." every time I add text in the Entry, However. I don't understand how to get the label to change from "Hello World" to "CHANGED!".

I assume I need the trace_add in lsv . But I can't figure out exactly what else I need to do. The trace_add requires a callback function, so I tried just setting one that returns. (func2)

Would appreciate your help! Thanks

Answer 1

You're making things too hard. All you need is one StringVar that is the textvariable of both the Entry and the Label . You're function func isn't really needed, but I left it in.

import tkinter
from tkinter import ttk


def func():
    print("func!")
#    sv.set("CHANGED!")  # Not needed.


root = tkinter.Tk()

frame = ttk.Frame(root)
frame.pack()

sv = tkinter.StringVar()
sv.trace_add("write", lambda *args: func())

entry = ttk.Entry(frame, textvariable=sv, width=25)
entry.pack()

label = ttk.Label(frame, textvariable=sv)
label.pack()

entry.focus_set()
root.mainloop()