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How to Build a Digital Clock in Python Tkinter

Step-by-step guide to creating a live-updating digital clock with Tkinter in Python, including 12/24-hour format toggle and date display using ttkthemes for styling.

Creating a digital clock is an excellent way to learn the basics of GUI programming in Python. This guide will walk you through building a desktop application using the tkinter library. The application will feature a live clock, current date display, and a toggle button to switch between 12-hour and 24-hour formats.

Prerequisites

We will use tkinter for the interface and ttkthemes to improve the visual style.

First, install the necessary libraries:

sudo apt-get install python3-tk -y
pip install ttkthemes

Step 1: Imports and Setup

Create a file named digital_clock.py. We begin by importing tkinter, styling modules, and the time formatting function.

import tkinter as tk
from tkinter import ttk
from ttkthemes import ThemedStyle
from time import strftime

Step 2: Defining the Logic

We need two core functions:

  1. time(): Fetches the current time, updates the label, and schedules itself to run again in 1 second.
  2. toggle_time_format(): Switches the global flag between 12-hour and 24-hour modes.
is_24_hour_format = True

def toggle_time_format():
    """Switches between 12-hour and 24-hour formats."""
    global is_24_hour_format
    is_24_hour_format = not is_24_hour_format
    time_format_button.config(text="12 Hour" if is_24_hour_format else "24 Hour")

def time():
    """Updates the time and date labels every second."""
    current_time_format = "%H:%M:%S" if is_24_hour_format else "%I:%M:%S %p"
    
    current_time = strftime(current_time_format)
    current_date = strftime("%A, %B %d, %Y")
    
    label_time.config(text=current_time)
    label_date.config(text=current_date)
    
    label_time.after(1000, time)

Step 3: Creating the GUI

We initialize the main window, apply a theme, and arrange our widgets (Labels and Button) using a Frame.

root = tk.Tk()
root.title("Digital Clock")
root.geometry("400x250")

style = ThemedStyle(root)
style.set_theme("plastik")  # Options: plastik, arc, radiance, etc.

style.configure("TLabel", foreground="#FF5733", background="#333333")
style.configure("TButton", foreground="#FF5733", background="#333333", font=("calibri", 10, "bold"))
style.configure("TFrame", background="#333333")

frame = ttk.Frame(root, style="TFrame", padding=20)
frame.place(relx=0.5, rely=0.5, anchor="center")

label_time = ttk.Label(frame, font=("calibri", 48, "bold"))
label_time.pack()

label_date = ttk.Label(frame, font=("calibri", 16))
label_date.pack()

time_format_button = ttk.Button(
    frame, 
    text="12 Hour", 
    command=toggle_time_format, 
    style="TButton"
)
time_format_button.pack(pady=20)

Step 4: Running the Application

Finally, trigger the first update manually and start the main event loop.

time()

root.mainloop()

To run the application:

python digital_clock.py

Conclusion

You have successfully built a GUI application in Python.

  1. tk.Tk() creates the main window.
  2. root.mainloop() keeps the window open and listening for events.
  3. widget.after() allows for periodic updates (like a clock tick) without freezing the UI.
  4. strftime provides flexible string formatting for time and date objects.
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