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))
        self.timer_label.pack(pady=20)

        # 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
        self.update_timer()

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

    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.timer_label.config(text=time_str)
            self.root.after(1000, self.update_timer)  # Update every 1 second

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

Explanation:

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()".

Output:

Flowchart:

Python Code Editor:

Previous: Freehand drawing and undo.
Next: Create menu options.