Raspberry pi - Flash 2 LEDs on and off triggered by a button press (button is wired with pulldown resistor)

sirenLights.py

# Write your code here :-)
import time
import RPi.GPIO as GPIO

GPIO.setmode(GPIO.BCM)

# Define LEDs
GREEN_LED=14
RED_LED=4
# Setup LEDs
GPIO.setup(GREEN_LED, GPIO.OUT)
GPIO.setup(RED_LED, GPIO.OUT)
# Define Button
BUTTON = 15
# Setup Button
GPIO.setup(BUTTON, GPIO.IN, pull_up_down=GPIO.PUD_DOWN)
# Set initial state for run loop
pressed = False

def button_pressed(channel):
    global pressed
    pressed = not pressed

GPIO.add_event_detect(BUTTON, GPIO.RISING, callback=button_pressed, bouncetime=500) # setup the callback for the button pressed event

def lights_out():
    GPIO.output(GREEN_LED, False)
    GPIO.output(RED_LED, False)               
i=0

while True:
    if pressed:                   
        # set pin to other pin every iteration
        if i%2 == 0:
            pin=GREEN_LED                
        else:
            pin=RED_LED
        
        GPIO.output(pin, True)
        time.sleep(0.25)
        GPIO.output(pin, False)
        time.sleep(0.25)
        i+=1
    else:
        lights_out()
        i=0