event.py

import simplegui

size = 10
radius = 10

# Define event handlers
def incr_button_handler():
    """Increment the size"""
    global size
    size += 1
    label.set_text("Value: "+str(size))

def decr_button_handler():
    """Decrement the size"""
    global size
    if size > 1:
        size -= 1
        label.set_text("Value: "+str(size))

def change_circle_handler():
    """Change the circle radius"""
    global radius
    radius = size
    radius_label.set_text("Radius: "+str(radius))

def draw_handler(canvas):
    """Draw the circle"""
    canvas.draw_circle((100, 100), radius, 5, "Red")

# Create a frame and assign callback to event handlers.
frame = simplegui.create_frame("Home", 200, 200)
label = frame.add_label("Value: "+str(size))
frame.add_button("Increase", incr_button_handler)
frame.add_button("Decrease", decr_button_handler)
radius_label = frame.add_label("Radius: "+str(radius))
frame.add_button("Change circle", change_circle_handler)
frame.set_draw_handler(draw_handler)

# Start the frame animation
frame.start()