Binding multiple events on Tkinter Entry?

Question

I want to capture the time(in milliseconds) taken by a person to type a password, that is, from the first key press to the time the person presses Enter button. To accomplish this, I have the following code:

import tkinter as tk
import time

class MyApp(object):
    start=0.0
    end=0.0
    total_time=0.0
    def __init__(self, master):
        self.pass1 = tk.Entry(master,show="*")
        self.pass1.bind('<Key>', self.callback1)
        self.pass1.pack()

    def callback1(self, event): # Called Only by first key press
        self.start=time.time()*1000.0 # start variable must be modified ONLY by  first key press

    def callback2(self,event): # called by Enter Key press
        self.end=time.time()*1000.0
        self.total_time=self.start-self.end
        print(self.totaltime)

root = tk.Tk()
app = MyApp(root)
root.mainloop()

The problem I am having is I am not able to bind callback1and callback2 on pass1. What I wanted was that when a person hit the first key of their password, startis set to the current time and when the person press Enter endis initialized to the current time. I hope these two would give me an approximate of the time.

How can i modify the program above to accomplish what I want? Thanks.

Answer 1

Firstly, you need to bind callback2 to the Enter / Return Key this is done using '<Return>'.

def __init__(self, master):
    self.pass1 = tk.Entry(master,show="*")
    self.pass1.bind('<Key>', self.callback1)
    self.pass1.bind('<Return>', self.callback2) # callback2 bound to Enter / Return key
    self.pass1.pack()

Next, you want to only allow callback1 to run once. To do this, unbind it from the widget like so

def callback1(self, event):
    self.start=time.time()*1000.0 
    self.pass1.unbind('<Key>') # unbind callback1

And then finally rebind it once the Enter key is pressed, so in the callback2 function

def callback2(self,event): # called by Enter Key press
    self.end=time.time()*1000.0
    self.total_time=self.end-self.start
    print(self.total_time)
    self.pass1.bind('<Key>', self.callback1) # rebind callback1

Side Notes:

As you can see I changed the ordering for the time to end - start instead of what you had before which was start - end which gives you a negative value.

I also suggest changing '<Key>' to '<KeyRelease>'

Your other options if you don't want to unbind the function is to use an if statement checking if self.start has a value.

if self.start == 0.0:
    self.start=time.time()*1000.0

You should also put your variables inside the __init__ function.

def __init__(self, master):
    self.start=0.0
    self.end=0.0
    self.total_time=0.0
    ...