Change Background colour of Entry widget based on number of chars entered

Change in background colour using config()

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.

str1.trace_add('write',my_bg) # trigger when varaible changes

More about StringVar()

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 ) .

We used one if elif code block to configure the background colour of the Entry box.

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')

Change in background colour based on Number of chars entered in Tkinter

Full code is here

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()

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Subhendu Mohapatra

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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.

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Configure Background based on Number of Chars

trace() method

Function my_bg()

Subhendu Mohapatra