python - Tkinter: Change button background when pressed

Question

I know that I should use bttn['text'] = 'text', but I'm creating buttons by for. I want to button changing its colour for red when it presssed.

Example code:

from tkinter import *

root = Tk()

btn = [i for i in range(10)]

for i in range(len(btn)):
    b = Button(root, text=str(i), command=lambda c=i: print(i))
    b.pack()

root.mainloop()

What need I replace instead print(i)?

Answer 1

To do that you need to pass the Button object "b" into the callback function. In order to do that you need to set the command on the next line, so that the "b" object is available. Like this:

from tkinter import *

root = Tk()

def change_to_red(bttn):
    bttn.config(bg='red', activebackground='red') # same as bttn['bg'] = 'red';  bttn['activebackground'] = 'red'
    print(bttn['text'])

btn = [i for i in range(10)]

for i in range(len(btn)):
    b = Button(root, text=str(i), width=6)
    b.config(command=lambda c=b: change_to_red(c))
    b.pack()

root.mainloop()

But actually this would be a great place to learn about subclasses. You can modify tkinter's Button to make your own type of Button that does what you want in addition to it's normal actions:

import tkinter as tk

class Desync192Button(tk.Button):
    def __init__(self, master=None, **kwargs):
        self.command = kwargs.pop('command', None)
        super().__init__(master, command=self.on_click, **kwargs)
    def on_click(self):
        self.config(bg='red', activebackground='red')
        if self.command: self.command()

# demo:
root = tk.Tk()

for i in range(10):
    b = Desync192Button(root, text=i, width=6, command=lambda c=i: print(c))
    b.pack()

root.mainloop()