How to Validate a Textbox in Python

In different software development environments, working with different modes of input is very common. One such element is the textbox.

They’re used to capture string input from users. In Python, due to its wide application, especially in graphical user interface (GUI) development, textboxes serve as a key input source.

In this tutorial, we are going to learn how to validate a textbox in Python using TKinter, which is one of the most utilized GUI toolkits.

Step 1: Install the TKinter Module

First things first, we need to ensure that the TKinter library is installed on our system. Luckily, if you have Python version 3.1 or above installed, this library comes as standard. If not, you can install it via pip:

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pip install python-tk

Step 2: Import the TKinter Module

Having ensured the library is installed on your system, the next step is to import it into your script:

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import tkinter as tk
from tkinter import messagebox

Step 3: Create the Textbox and Validation Function

The next step is to create the textbox using the TKinter module and make an accompanying function that is going to be used to validate data entered into the textbox.

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root = tk.Tk()
 
def validate():
    if textbox.get().isdigit():
        messagebox.showinfo("Information","Input is valid")
    else:
        messagebox.showinfo("Warning","Please enter only numeric input")
 
textbox = tk.Entry(root)
textbox.pack()
 
button = tk.Button(root, text = "Check", command = validate)
button.pack()
 
root.mainloop()

In the above code, we first created a tkinter window (root), and then we created an entry widget (textbox) where the user can enter their input. We also created a button that when clicked, calls the validate function.

The validate() function checks if the entered string in the textbox is numeric (using the str.isdigit() method) and if true, it displays a message box saying “Input is valid”, otherwise it shows a warning “Please enter only numeric input”.

Complete Code

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import tkinter as tk
from tkinter import messagebox
 
root = tk.Tk()
 
def validate():
    if textbox.get().isdigit():
        messagebox.showinfo("Information","Input is valid")
    else:
        messagebox.showinfo("Warning","Please enter only numeric input")
 
textbox = tk.Entry(root)
textbox.pack()
 
button = tk.Button(root, text = "Check", command = validate)
button.pack()
 
root.mainloop()

Text:

Number:

Conclusion

Textbox validation is an essential step in ensuring data integrity when capturing user inputs. With tkinter and Python, this process is not only seamless but quite versatile given the functions offered by the tkinter module for different validation conditions.

Always remember, that user input is a doorway for potential errors in your application. Therefore, validating this data keeps your application robust and reliable.