Create a stopwatch using python

This article focus on creating a stopwatch using Tkinter in python 
Tkinter : Tkinter is the standard GUI library for Python. Python when combined with Tkinter provides a fast and easy way to create GUI applications. Tkinter provides a powerful object-oriented interface to the Tk GUI toolkit. It’s very easy to get started with Tkinter, here are some sample codes to get your hands on Tkinter in python. 

Python3

# Python program to illustrate a stop watch
# using Tkinter
#importing the required libraries
import tkinter as Tkinter
from datetime import datetime
counter = 66600
running = False
def counter_label(label):
    def count():
        if running:
            global counter

            # To manage the initial delay.
            if counter==66600:
                display="Starting..."
            else:
                tt = datetime.fromtimestamp(counter)
                string = tt.strftime("%H:%M:%S")
                display=string

            label['text']=display   # Or label.config(text=display)

            # label.after(arg1, arg2) delays by
            # first argument given in milliseconds
            # and then calls the function given as second argument.
            # Generally like here we need to call the
            # function in which it is present repeatedly.
            # Delays by 1000ms=1 seconds and call count again.
            label.after(1000, count)
            counter += 1

    # Triggering the start of the counter.
    count()

# start function of the stopwatch
def Start(label):
    global running
    running=True
    counter_label(label)
    start['state']='disabled'
    stop['state']='normal'
    reset['state']='normal'

# Stop function of the stopwatch
def Stop():
    global running
    start['state']='normal'
    stop['state']='disabled'
    reset['state']='normal'
    running = False

# Reset function of the stopwatch
def Reset(label):
    global counter
    counter=66600

    # If rest is pressed after pressing stop.
    if running==False:
        reset['state']='disabled'
        label['text']='Welcome!'

    # If reset is pressed while the stopwatch is running.
    else:
        label['text']='Starting...'

root = Tkinter.Tk()
root.title("Stopwatch")

# Fixing the window size.
root.minsize(width=250, height=70)
label = Tkinter.Label(root, text="Welcome!", fg="black", font="Verdana 30 bold")
label.pack()
f = Tkinter.Frame(root)
start = Tkinter.Button(f, text='Start', width=6, command=lambda:Start(label))
stop = Tkinter.Button(f, text='Stop',width=6,state='disabled', command=Stop)
reset = Tkinter.Button(f, text='Reset',width=6, state='disabled', command=lambda:Reset(label))
f.pack(anchor = 'center',pady=5)
start.pack(side="left")
stop.pack(side ="left")
reset.pack(side="left")
root.mainloop()

Output:

Creating Stopwatch using Tkinter

Now lets try to create a program using Tkinter module to create a stopwatch. 
A stopwatch is a handheld timepiece designed to measure the amount of time elapsed from a particular time when it is activated to the time when the piece is deactivated. A large digital version of a stopwatch designed for viewing at a distance, as in a sports stadium, is called a stop clock. In manual timing, the clock is started and stopped by a person pressing a button. In fully automatic time, both starting and stopping are triggered automatically, by sensors. 
Required Modules: We are only going to use Tkinter for creating GUI and no other libraries will be used in this program.
Source Code:

Output: