Steps to Validate Entry Widget in Tkinter

There are a number of ways to validate an Entry widget. Here we will create a Tkinter window which will have a label, an entry widget, and a button. When the user enters some data in the Entry widget and clicks the Button, a function is called to validate the data entered by the user. It will then display a message popup window displaying whether the data is valid or invalid.

Let us see the steps to create such a validity check on the Entry widget.

Import Modules

The first step is to import the modules, that is the Tkinter and messagebox widget. The Tkinter module is used to create the main window application and other widgets whereas the messagebox widget is used for a popup window that displays a message.

import tkinter as tk
from tkinter import messagebox

Create Tkinter Window

Next, create the main application window using tk.Tk() class. It is the parent or root window that contains all other Tkinter widgets such as buttons, labels, entries, etc. We can also provide a title and dimensions for the Tkinter window.

root = tk.Tk()
root.title("title_to_display")
root.geometry("300x200")

Create Required Widgets

Add the necessary widgets that you want to display on the Tkinter window. Here we require three widgets – Label, Entry, and Button.

label = tk.Label(root, text="text_to_display")
entry = tk.Entry(root)
btn = tk.Button(root, text="text_to_display")
label.pack()
entry.pack()
btn.pack()

Define Validation Function

Create a function to validate the input based on specific criteria, such as checking for only digits, and alphabets and making sure the entry widget is not empty.

data.isdigit()
data.isalpha()

Bind Validation to Submit Button

Validate the input when the user presses the submit button. The Button() function’s third parameter, that is command will have the value of a function name that is to be called when the button is clicked. This function will check for validity.

btn = tk.Button(root, text="text_to_display", command=function_to_call)

Run the Main Event Loop

Finally, run the main event loop to display the window and make the application responsive to user interactions.

root.mainloop()

When developing graphical user interfaces (GUIs) in Python, Tkinter is a powerful and widely-used toolkit that simplifies the process. One of the common tasks in GUI applications is obtaining user input through form fields. Tkinter’s Entry widget is designed for this purpose, allowing users to input text. However, ensuring the correctness of the entered data is crucial. This article will discuss how to validate input in the Entry widget using Tkinter, providing practical examples to illustrate the concept.