We can validate a text entry in Tkinter with the help of callback functions of button widget in tkinter.
Button classThe Button class is used to create buttons in tkinter.
The syntax to create a button is as follows:
ttk.Button(parent, options)
parent: This is the parent component on which the button will be placed.options: There are a lot of options. Some of the important options we use in this answer are as follows:| Option | Description |
|---|---|
text |
The text to display on the button. |
padx |
Padding to the button in x or horizontal direction. |
pady |
Padding to the button in y or vertical direction. |
command |
The callback function to be called. |
Let’s learn this with the help of an example.
We build a simple GUI using Python Tkinter. Firstly, we create a simple interface to accept the user input and a submit button. When the user clicks on the submit button, a validation function is invoked.
import tkinter as tk
from tkinter import messagebox
window_screen = tk.Tk()
window_screen.title('Validation Demo')
window_screen.geometry('300x200')
def validation():
text = text_tf.get()
msg = "The input text is correct"
if len(text) == 0:
msg = "The text can\'t be empty"
elif len(text) > 20:
msg = "The text can\'t be greater than 20 characters"
messagebox.showinfo('message', msg)
frame = tk.Frame(window_screen, padx=10, pady=10)
frame.pack(pady=20)
tk.Label(frame, text='Enter Text').grid(row=0, column=0)
text_tf = tk.Entry(frame, font=('calibre',10,'normal'))
text_tf.grid(row=0, column=1)
tk.Button(frame, text='Submit', pady=10, padx=20, command=validation).grid(row=1, columnspan=2)
window_screen.mainloop()
Lines 1–2: We import the relevant dependencies.
Line 4: We create an instance of Tk() called window_screen.
Line 5: We set the title of the window_screen using the title() method.
Line 6: We set the shape of the window_screen using the geometry() method.
Lines 8–17: We define a method called validation() which gets called when the submit button is clicked.
Line 9: We retrieve the content of the text entry using the get() method.
Line 10: A variable called msg is defined that contains the message to be shown to the user after the validation.
Lines 12–15: We check if the input text is empty or more than 20 characters.
Line 17: We use the message box to show the validation result to the user.
Line 19: A frame called frame is created.
Line 22: A label for the text entry widget is created.
Line 23: A text entry widget is created with the help of the Entry class.
Line 25: A button is created with the command parameter set to the validation function. The validation function is invoked once the button is clicked.
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