How Can I Create Blinking Rectangle Animations Using Tkinter's `after()` Method?

Executing Functions over Time in Tkinter

In event-driven programming, the application runs continuously, responding to events as they occur. Rather than executing functions sequentially, event-driven programming places functions on a queue to execute at specific times.

Case Study: Blinking Rectangle Animation

To create a blinking rectangle animation in Tkinter, we can define a function for the animation and schedule it to run at intervals. Here's how to approach the problem:

1. Define the Animation Function:

def blink(rect, canvas):
    current_color = canvas.itemcget(rect, "fill")
    new_color = "red" if current_color == "white" else "white"
    canvas.itemconfigure(rect, fill=new_color)

This function toggles the rectangle's color between red and white.

2. Schedule the Function:

To make the rectangle blink repeatedly, we schedule the blink function to run after specified intervals:

root.after(1000, blink, rect, canv)
root.after(2000, blink, rect, canv)
root.after(3000, blink, rect, canv)

After one, two, and three seconds, the rectangle's color will change accordingly.

3. Iterate the Animation (Optional):

To make the animation run indefinitely, we can call the blink function within itself:

def blink(rect, canvas):
    ...
    canvas.after(1000, blink, rect, canvas)

This approach continues the animation indefinitely until a stop condition is met (e.g., a button click).

4. Class-Based Approach (Optional):

For larger programs, it's recommended to organize the code as a class:

from tkinter import *

classMyApp(Tk):
    def __init__(self):
        ...
        self.start_button = Button(self, text="start blinking", command=self.start_blinking)
        ...

    def start_blinking(self):
        ...
        canvas.after(1000, self.blink)

This approach encapsulates the animation logic within a class, making it easier to manage.

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