Python script for Raspberry Pi to alternate flashing of two LEDs with two buttons for modifying the duration of the delays between alternations.

flashingledswithbuttoncontrolleddelay.py

from gpiozero import LED, Button
from time import sleep

minimum = 0.0625
maximum = 1.00
increment = 0.0625
delay = minimum

def set_delay(offset):
    global delay, minimum, maximum
    newdelay = delay + offset
    if newdelay >= minimum and newdelay <= maximum:
        print("set " + str(newdelay))
        delay = newdelay
    else:
        print("not set " + str(newdelay))

def increase_delay():
    global increment
    set_delay(increment)

def decrease_delay():
    global increment
    set_delay(-increment)

greenled = LED("GPIO04")
redled = LED("GPIO18")
upbutton = Button("GPIO26")
downbutton = Button("GPIO20")
upbutton.when_released = increase_delay
downbutton.when_released = decrease_delay
while True:
    greenled.on()
    redled.off()
    sleep(delay)
    greenled.off()
    redled.on()
    sleep(delay)