What I have at the moment is the below loop which lights each led on a strand of 24 in turn.

```
while True:
    for i in range(24):
        pixels = [ (0,0,0) ] * numLEDs
        pixels[i] = (100, 100, 100)
        client.put_pixels(pixels)
        time.sleep(0.02) 

```

What I would like to have is that the previously lit leds stay on for each iteration. So the number of lit leds increases by one each time round.

I assumed I could simply select from the start of the list to the i'th item as below.
However this returns a "TypeError: 'int' object is not iterable".

I'm not really clear why this doesn't work.

```
while True:
    for i in range(24):
        pixels = [ (0,0,0) ] * numLEDs
        pixels[:i] = (100, 100, 100)
        client.put_pixels(pixels)
        time.sleep(0.02) 

```

While I've got your attention, is there a better way to time these loops other than using time.sleep()? Although I am using threading, the sleeps still cause some delays when the led patterns change.