Getting real time data in Tkinter

Consider the code below:

from tkinter import *

screen = Tk()

e =Entry()
e.pack()


screen.mainloop()

Now how to get to display the length of the characters entered in the e entry widget in real-time? It doesn't matter if the data is displayed in the GUI or Corresponding terminal

Solution

There are atleast 3 ways to do this here with one being better than the other:

Using trace from StringVar:

def func(*args):
    print(len(var.get()))

var = StringVar()

e = Entry(screen,textvariable=var)
e.pack()

var.trace('w',func)

Every time the value of var is changed, func will be called.

Using bind to each key release:

def func(*args):
    print(len(e.get()))

e.bind('<KeyRelease>',func)

Using after(ms,func) to keep repeating the function:

def func():
    print(len(e.get()))
    screen.after(500,func)

func()

As you can see, the first method is more efficient as it does not unnecessarily prints out values when you select all the items(with Ctrl+A) and so on. Using after() will be the most ridiculous method as it will keep printing the length always as there are no restrictions provided.