In this tutorial, I will explain how to master the Python Tkinter mainloop in detail with real-world examples. One of my team members asked me about Tkinter mainloop which made me explore more about this topic and I will share my experiences and provide a step-by-step guide to help you master Python Tkinter mainloop.
Python Tkinter Mainloop
The Tkinter mainloop() is an infinite loop that runs in the background of your Python GUI application. It waits for events to occur, such as user interactions (clicks, key presses) or system events, and processes them accordingly. The mainloop() keeps the application running until the user closes the window or the program explicitly calls the quit() method.
Read How to Cancel Scheduled Functions with after_cancel() in Python Tkinter?
Master the Python Tkinter Mainloop
Let’s get into some practical examples of using the Tkinter mainloop() in real-world scenarios specific to the United States.
Example 1: A Simple User Registration Form
Suppose you’re creating a user registration form for a website targeting users in the United States. Here’s how you can use Tkinter and the mainloop() to achieve this:
import tkinter as tk
from tkinter import ttk
def submit_form():
name = name_entry.get()
email = email_entry.get()
state = state_combobox.get()
print(f"Name: {name}")
print(f"Email: {email}")
print(f"State: {state}")
root = tk.Tk()
root.title("User Registration Form")
name_label = ttk.Label(root, text="Name:")
name_label.grid(row=0, column=0, padx=5, pady=5)
name_entry = ttk.Entry(root)
name_entry.grid(row=0, column=1, padx=5, pady=5)
email_label = ttk.Label(root, text="Email:")
email_label.grid(row=1, column=0, padx=5, pady=5)
email_entry = ttk.Entry(root)
email_entry.grid(row=1, column=1, padx=5, pady=5)
state_label = ttk.Label(root, text="State:")
state_label.grid(row=2, column=0, padx=5, pady=5)
state_combobox = ttk.Combobox(root, values=["California", "Texas", "Florida", "New York"])
state_combobox.grid(row=2, column=1, padx=5, pady=5)
submit_button = ttk.Button(root, text="Submit", command=submit_form)
submit_button.grid(row=3, column=0, columnspan=2, padx=5, pady=5)
root.mainloop()You can look at the output in the screenshot below.
In this example, we create a user registration form with fields for name, email, and state. The mainloop() is called at the end to start the event loop and keep the application running until the user closes the window. When the user clicks the “Submit” button, the submit_form() function is called, which retrieves the entered values and prints them.
Check out How to Create GUI Layouts with Python Tkinter Separator?
Example 2: A Tkinter Application with Multiple Windows
Let’s say you’re building a Tkinter application for a US-based company that requires multiple windows. Here’s how you can structure your code and use the mainloop():
import tkinter as tk
from tkinter import ttk
def open_settings_window():
settings_window = tk.Toplevel(root)
settings_window.title("Settings")
# Add widgets to the settings window
settings_window.mainloop()
root = tk.Tk()
root.title("Main Window")
main_label = ttk.Label(root, text="Welcome to the Main Window")
main_label.pack(padx=20, pady=20)
settings_button = ttk.Button(root, text="Open Settings", command=open_settings_window)
settings_button.pack(padx=20, pady=10)
root.mainloop()You can look at the output in the screenshot below.
In this example, we have a main window with a label and a button. When the “Open Settings” button is clicked, the open_settings_window() function is called, which creates a new window (Toplevel) for the settings. The mainloop() is called for both the main window and the settings window to ensure they remain responsive to user interactions.
Read How to Add Functions to Python Tkinter?
Example 3: A Tkinter Mainloop exit
Suppose you are building a Tkinter application for a US-based company that requires an exit button to exit from the window. Here’s how you can structure your code and use the mainloop():
from tkinter import *
ws = Tk()
ws.title('PythonGuides')
ws.geometry('300x200')
Button(
ws,
text='Exit',
command=lambda:ws.destroy()
).pack(expand=True)
ws.mainloop()Python Tkinter provides a destroy() function using which we can exit the mainloop in Python Tkinter. destroy() function can be applied on parent windows, frames, canvas, etc.
You can look at the output in the screenshot below.
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Handle the Mainloop Blocking Effect
One common issue developers face when using the Tkinter mainloop() is its blocking effect. Once the mainloop() is called, the program execution stays within that loop until the window is closed. This can be problematic if you need to perform other tasks concurrently.
To overcome this, you can use techniques like threading or the after() method to schedule tasks to run alongside the mainloop(). For example, if you want to update a label every second while the main window is running, you can use the after() method:
import tkinter as tk
from tkinter import ttk
import time
def update_time():
current_time = time.strftime("%H:%M:%S")
time_label.config(text=current_time)
root.after(1000, update_time)
root = tk.Tk()
root.title("Current Time")
time_label = ttk.Label(root, font=("Arial", 24))
time_label.pack(padx=20, pady=20)
update_time() # Start updating the time
root.mainloop()You can look at the output in the screenshot below.
In this example, the update_time() function is called initially and then scheduled to run every 1000 milliseconds (1 second) using the after() method. This allows the time to be updated continuously while the main event loop is running.
Read How to Create a Python Tkinter Panel with Search Functionality?
Best Practices for Using the Tkinter Mainloop
Here are some best practices to keep in mind when working with the Tkinter mainloop():
- Always call
mainloop()at the end of your Tkinter program to start the event loop and keep the application running. - If you have multiple windows in your application, call
mainloop()for each window to ensure they remain responsive. - Use techniques like threading or the
after()method to perform tasks concurrently with themainloop()when necessary. - Avoid blocking the
mainloop()with long-running tasks, as it will freeze your application. Instead, use appropriate concurrency mechanisms. - Keep your event handlers (callbacks) short and efficient to maintain a responsive user interface.
Check out How to Create Scrollable Frames with Python Tkinter?
Conclusion
In this tutorial, We discussed various examples to master the Python Tkinter mainloop like an example of a simple user registration form, a Tkinter application with multiple windows, and a Tkinter mainloop exit. We also learned how to handle the mainloop blocking effect and some best practices for using the Tkinter mainloop.
You may read:
- How to Display Images in Python Tkinter?
- How to Use Colors in Python Tkinter?
- How to Create a Text Box in Python Tkinter?
I am Bijay Kumar, a Microsoft MVP in SharePoint. Apart from SharePoint, I started working on Python, Machine learning, and artificial intelligence for the last 5 years. During this time I got expertise in various Python libraries also like Tkinter, Pandas, NumPy, Turtle, Django, Matplotlib, Tensorflow, Scipy, Scikit-Learn, etc… for various clients in the United States, Canada, the United Kingdom, Australia, New Zealand, etc. Check out my profile.
