Python - I want two entry widgets Sum without using button

Question

I do not understand how to do this. I need to sum of two entries and then put the sum into another entry widget without any Buttons.

Example one

from tkinter import *
def sum():
a=float(t1.get())
b=float(t2.get())
c=a+b
t3.insert(0,c)
win=Tk()
win.geometry('850x450')

l1=Label(win,text="First Number")
l1.grid(row=0,column=0)
t1=Entry(win)
t1.grid(row=0,column=1)

l2=Label(win,text="Second Number")
l2.grid(row=1,column=0)
t2=Entry(win)
t2.grid(row=1,column=1)

l3=Label(win,text="Result")
l3.grid(row=2,column=0)
t3=Entry(win)
t3.grid(row=2,column=1)

b1=Button(win,text="Click For SUM",command=sum)
b1.grid(row=3,column=1)

win.mainloop()

I hope anyone can handle this..

Thanks in advance..

Answer 1

You can run a function that regularly every one second resets the third entry's value to the sum of the first and the second like so-:

try :
    import tkinter as tk # Python 3
except :
    import Tkinter as tk # Python 2

def update_sum() :
    # Sets the sum of values of e1 and e2 as val of e3
    try :
        sum_tk.set((int(e1_tk.get().replace(' ', '')) + int(e2_tk.get().replace(' ', ''))))
    except :
        pass
    
    root.after(1000, update_sum) # reschedule the event
    return

root = tk.Tk()

e1_tk = tk.StringVar(root) # Initializes a text variable of tk to use to get e1's val.
e2_tk = tk.StringVar(root) # Initializes a text variable of tk to use to get e2's val.
sum_tk = tk.StringVar(root) # Initializes a text variable of tk to use to set e3's val.

# Entries
e1 = tk.Entry(root, textvariable = e1_tk)
e2 = tk.Entry(root, textvariable = e2_tk)
e3 = tk.Entry(root, textvariable = sum_tk)

e1.pack()
e2.pack()
e3.pack()

# Will update the sum every second 1000 ms = 1 second it takes ms as arg.
root.after(1000, update_sum)
root.mainloop()

You can adjust the delay between updates as you wish.