How to make specific text non-removable in tkinter?

In Tkinter, users can input text using two basic text input widgets − the Text widget and the Entry widget. The Text widget is generally used to accept multiline user input, whereas in an Entry widget, the user can type only single-line text.

You can customize these widgets and add additional functionality using built-in library functions and methods. To make specific text non-removable, you can use input validation with the register() method and validation commands.

Understanding Validation Parameters

To validate input in an Entry widget, use the config(**options) method and pass the validate and validatecommand arguments ?

• validate − Specifies when the callback function should be called for validating input. For example, "key" means the validation occurs whenever a user presses a key. Other options include focus, focusin, focusout, none, all.

• validatecommand − Specifies the callback function and passes validation data using substitution codes like %P (proposed text) or %S (inserted/deleted text).

Method 1: Using startswith() Validation

This approach validates that the text always starts with a specific non-removable prefix ?

# Import required libraries
from tkinter import *

# Create an instance of tkinter window
win = Tk()
win.geometry("700x350")
win.title("Non-removable Text Example")

# Define a function to make a text non-removable
def make_non_removable(proposed_text):
    return proposed_text.startswith("Enter your Email Id: ")

# Create an entry widget
entry = Entry(win, bg="black", fg="white", font=("Arial", 12))
entry.pack(side="top", fill="x", padx=10, pady=20)

# Add a default text
entry.insert(0, "Enter your Email Id: ")

# Register the validation function
validate_entry = (win.register(make_non_removable), '%P')
entry.config(validate='key', validatecommand=validate_entry)

win.mainloop()

Method 2: Using Text Widget with Read-only Sections

For more complex scenarios, you can use a Text widget with tags to make specific portions read-only ?

from tkinter import *

def on_key_press(event):
    # Get cursor position
    cursor_pos = text.index(INSERT)
    
    # Check if cursor is in the protected area (first 19 characters)
    if text.compare(cursor_pos, "<=", "1.19"):
        if event.keysym in ['BackSpace', 'Delete']:
            return "break"  # Prevent deletion
    return None

# Create window
win = Tk()
win.geometry("700x350")
win.title("Protected Text Example")

# Create text widget
text = Text(win, bg="lightgray", fg="black", font=("Arial", 12))
text.pack(fill="both", expand=True, padx=10, pady=20)

# Insert protected text
protected_text = "Enter your Email Id: "
text.insert("1.0", protected_text)

# Bind key events
text.bind("<KeyPress>", on_key_press)

# Position cursor after protected text
text.mark_set(INSERT, "1.19")

win.mainloop()

How It Works

The validation approach works by:

• Registration − The callback function is registered using win.register()

• Validation − On each keystroke, the function checks if the proposed text starts with the required prefix

• Return Value − If validation passes, it returns True; otherwise False, preventing the change

Comparison

Conclusion

Use startswith() validation for simple non-removable prefixes in Entry widgets. For more complex scenarios with formatting or multiline text, use Text widgets with event binding to protect specific regions.