How to Setup Change Event for Entry Widget in Tkinter Python

Setup Change Event for Entry Widget in Tkinter Python

In Tkinter, the Entry widget is used to accept single-line text input. To detect changes in the input field, we can use a Tkinter StringVar variable with a trace callback.

By setting up a change event, we can execute a function whenever the user types or modifies the input in the Entry widget.

Examples

1. Using StringVar with trace_add for Entry Widget

Another approach to detect text changes is by using a Tkinter StringVar variable. The trace_add method monitors changes and executes a callback function.

import tkinter as tk

def on_text_change(*args):
    print("Updated text:", text_var.get())

root = tk.Tk()
root.title("Entry Change Event - tutorialkart.com")
root.geometry("400x200")

# StringVar to track changes
text_var = tk.StringVar()
text_var.trace_add("write", on_text_change)

entry = tk.Entry(root, textvariable=text_var)
entry.pack(pady=10)

root.mainloop()

Output in Windows:

As the user types, the updated text is printed to the console.

2. Displaying Live Changes in a Label when Value in Entry Widget Changes

We can also update a Label dynamically as the user types in the Entry widget.

import tkinter as tk

def on_text_change(*args):
    label.config(text="You typed: " + text_var.get())

root = tk.Tk()
root.title("Entry Change Event - tutorialkart.com")
root.geometry("400x200")

text_var = tk.StringVar()
text_var.trace_add("write", on_text_change)

entry = tk.Entry(root, textvariable=text_var)
entry.pack(pady=10)

label = tk.Label(root, text="You typed: ")
label.pack(pady=10)

root.mainloop()

Output in Windows:

As the user types, the label updates dynamically to reflect the input.

Conclusion

In this tutorial, we explored different methods to detect and handle change events in Tkinter’s Entry widget:

• Using the <<Modified>> event to trigger changes.
• Using a StringVar with trace_add to monitor text updates.
• Displaying live updates using a Label.

These methods help in real-time text validation, search suggestions, and dynamic UI updates in Tkinter applications.