LED Patterns with Loops and Arrays

The big idea: once you can control one LED with your Raspberry Pi Pico, controlling six is not six times harder — it is almost the same amount of code. The trick is to stop copying and pasting one command per LED, and instead put all your LEDs into a single list (also called an array) and then walk through that list with a for loop.

In this lesson you will turn a row of little lights into animations: lights that chase each other, bounce back and forth, count in binary, sparkle randomly, and even act as a real traffic light. Every one of these effects is just a list of LEDs plus a clever loop. Master this and you have unlocked the core skill behind almost every light show, scoreboard, and status display ever built.

What you will be able to do

Wire 4 to 6 LEDs, each on its own GPIO pin, each with its own resistor.
Store many Pin objects in one Python list and understand what a list actually is.
Use a for loop to turn all LEDs on or off with just two or three lines.
Build a running light (the famous "Knight Rider" chase) and a bounce effect.
Show numbers in binary on your LEDs, and understand what binary means.
Make a random sparkle using the random module.
Wrap each pattern in a function so you can reuse it by name.
Change the animation speed from a single variable.
Understand why time.ticks_ms() can be better than sleep() (non-blocking timing).
Build a working traffic light and fix the two most common wiring/order bugs.

1. Wiring 4 to 6 LEDs

An LED (Light-Emitting Diode) is a tiny light that only lets electricity flow one way. It has two legs:

The long leg is the anode (the plus, + side). This connects toward the GPIO pin.

LED Patterns with Loops and Arrays