My standard "Hello, world" for a micro-controller with a NeoPixel on it.

neopixel_test.py

# Based on code from Adafruit Industries
# SPDX-License-Identifier: MIT
"""Rob's CircuitPython blink example for built-in NeoPixel LED"""
import time
import board
import neopixel
import random


k = 20 # number of steps up or down

def fade_in_and_out(pix, r, g, b):
    """Fade up from black to the indicated color, then down again, in 1 second."""
    for i in range(k):
        pix.fill((i*r/k, i*g/k, i*b/k))
        time.sleep(.5/k)
    for i in range(k, 0, -1):
        pix.fill((i*r/k, i*g/k, i*b/k))
        time.sleep(.5/k)


pixel = neopixel.NeoPixel(board.NEOPIXEL, 1)
pixel.fill((0, 0, 0)) # black

while True:
    r = random.randint(0, 255)
    g = random.randint(0, 255)
    b = random.randint(0, 255)
    # print(f"({r},{g},{b})")
    fade_in_and_out(pixel, r, g, b)