从Tkinter Entry小部件自动更新变量

Question

I am trying to make a real-time searching algorithm in GUI with tkinter in Python 3. So I have this window and entry box for typing keywords in for searching:

from tkinter import *

root = Tk()
root.geometry('800x400')
root.resizable(False,False)
root.title('Window')

var = StringVar()

root.SearchBox = ttk.Entry(root, textvariable=var, font='Fixedsys 28')
root.SearchBox.place(relx=0.5, rely=0.5, height=50, width=400, anchor="center")
search_input = var.get()

What should I put here, without an enter button for the search box

...Some codes here...

To get the following results?

When the tkinter window is already open and some keywords typed into the search entry box

>>>print(search_input)
Search Terms

and as soon as the search entry box search_input =! '' search_input =! '' how could I get a global variable to change, say is_entry_box_empty = False to is_entry_box_empty = True

I found this to be impossible without threading, since the GUI window will block any codes after it.

Many thanks

Answer 1

You can trace changes in the textvariable:

var.trace('w',var_change_callback_function)

and write a function to deal with the changes.