Configure Background based on Number of Chars
Managing background colour of Tkinter Entry based on number of chars entered by user using config()
trace() method
Our string variable str1 trace() method triggers the callback function my_bg() when the value of str1 changes[cite: 10].str1.trace_add('write',my_bg) # trigger when varaible changes Function my_bg()
We use the get() method of string variable str1 to read the string entered by the user and then used len() function to calculate the number of chars in the user entered string ( variable x )[cite: 10].We used one if elif code block to configure the background colour of the Entry box[cite: 10].
def my_bg(*args):
x=len(str1.get()) # Number of chars entered
str2.set(x) # Display the number ( value of x)
if(x<=3): # check value of x
e1.config(bg='red')
elif(x<=6):
e1.config(bg='yellow')
elif(x<=9):
e1.config(bg='lightgreen')
Full code is here[cite: 10]
import tkinter as tk
my_w = tk.Tk()
my_w.geometry("400x200") # Size of the window
my_w.title("www.plus2net.com") # Adding a title
font1 = ("Times", 26, "normal") # increase the font size and style
def my_bg(*args):
x = len(str1.get()) # Number of chars entered
str2.set(x) # Display the number (value of x)
if(x <= 3): # check value of x
e1.config(bg="red")
elif(x <= 6):
e1.config(bg="yellow")
elif(x <= 9):
e1.config(bg="lightgreen")
str1 = tk.StringVar(my_w) # declare StringVar()
str2 = tk.StringVar() # to show number of chars entered
l1 = tk.Label(my_w, textvariable=str2, width=5, font=font1)
l1.grid(row=0, column=0) # show the number of chars entered
e1 = tk.Entry(my_w, textvariable=str1, font=font1, width=10)
e1.grid(row=0, column=1, pady=20)
# str1.trace('w', my_bg) # trace is deprecated
str1.trace_add('write', my_bg) # trigger when variable changes
my_w.mainloop()Frequently Asked Questions (FAQ)
You can bind an Entry widget to a StringVar and use the
trace_add() method to listen for 'write' operations. This automatically triggers a callback function whenever the user inputs or deletes characters inside the Entry box. For more advanced input control, check out our guide on data validation.
Tkinter Entry Show Hide Password Using Checkbutton Tkinter Text How to Validate user entered data
Subhendu Mohapatra
Author & Instructor at plus2net
I write and maintain practical tutorials on Python, PHP, SQL, JavaScript, HTML, jQuery, and web development at plus2net. The tutorials focus on clear explanations, working examples, and code that readers can test and adapt while learning.
Connect:
Subscribe to our YouTube Channel here
This article is written by plus2net.com team.
https://www.plus2net.com
Python Video Tutorials