I have a raspberry PI 2. With a relay board, what i use to for a switch sequence (like a traffic light). 
I use a tool, called "webiopi" what create buttons on a website. When the button is clicked the function of the python script below is started. 

What i want is to break out of the loop (or pause it) when another button is clicked. However, as long this loop is running, the tool don't look at the webpage 

A kind of similar question is asked here [Exiting a continuous loop in python via webiopi](https://stackoverflow.com/questions/33400886/exiting-a-continuous-loop-in-python-via-webiopi) but this is for a single event and the solution doesn't work in my case. 

Question is. How can I make this script look at a button what is clicked (can be a gpio switch as well) while the loop is running

```
GPIO_nek=11 
GPIO_schouder=12
GPIO_rug1=8
GPIO_ONOFF=18
interval1 = 2
interval2 = 4
for x in range(0, 20):
    GPIO.digitalWrite(GPIO_nek, GPIO.LOW)
    time.sleep(interval1)
    GPIO.digitalWrite(GPIO_schouder, GPIO.LOW)
    time.sleep(interval1)
    GPIO.digitalWrite(GPIO_nek, GPIO.HIGH)
    time.sleep(interval1)
    GPIO.digitalWrite(GPIO_rug1, GPIO.LOW)
    time.sleep(interval2)
    GPIO.digitalWrite(GPIO_schouder, GPIO.HIGH)
    if (GPIO.digitalRead(GPIO_ONOFF) == GPIO.LOW):
        GPIO.digitalWrite(GPIO_ONOFF, GPIO.HIGH)
        break

```