Python Tkinter timer App - Countdown timer

Python Tkinter Events and Event Handling: Exercise-10 with Solution

Write a Python program that builds a timer application using Tkinter. The application starts a countdown when a "Start" button is clicked and stops when a "Stop" button is clicked.

Sample Solution:

Python Code:

import tkinter as tk

class TimerApp:
    def __init__(self, root):
        self.root = root
        self.root.title("Timer App")

        # Initialize timer variables
        self.seconds = 0
        self.timer_running = False

        # Create a label to display the timer
        self.timer_label = tk.Label(root, text="00:00", font=("Helvetica", 48))

        # Create Start and Stop buttons
        self.start_button = tk.Button(root, text="Start", command=self.start_timer)
        self.stop_button = tk.Button(root, text="Stop", command=self.stop_timer)
        self.start_button.pack(side=tk.LEFT, padx=10)
        self.stop_button.pack(side=tk.LEFT, padx=10)

        # Update the timer display

    def start_timer(self):
        if not self.timer_running:
            self.timer_running = True

    def stop_timer(self):
        self.timer_running = False

    def update_timer(self):
        if self.timer_running:
            self.seconds += 1
            minutes = self.seconds // 60
            seconds = self.seconds % 60
            time_str = f"{minutes:02}:{seconds:02}"
            self.root.after(1000, self.update_timer)  # Update every 1 second

if __name__ == "__main__":
    root = tk.Tk()
    app = TimerApp(root)


In the exercise above -

  • Import the "tkinter" library.
  • Create a "TimerApp" class that represents the timer application.
  • The 'init' method initializes the main application window and timer variables. Additionally, labels are created for displaying the timer and buttons for starting and stopping it.
  • The "start_timer()" method starts the timer by setting the timer_running flag to True.
  • The "stop_timer()" method stops the timer by setting the timer_running flag to False.
  • The "update_timer()" method is called repeatedly if the timer is running. The timer is incremented by one second and the timer display is updated.
  • Finally, start the Tkinter main loop with "root.mainloop()".


Tkinter: Countdown timer. Part-1
Tkinter: Countdown timer. Part-2


Flowchart: Countdown timer.
Flowchart: Countdown timer.

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