Lists in Python

Support
#1

I have a project using the Plasma 2040 programmed in Python. I have a Python list of 8 items which I wish to step through sequentially for each press of the “Boot” button but to then return to the first item when I reach the last in the list and start again, “ad infinitum” (or at least until I switch Off!). Any thoughts?

#2

Demo below on a method using Pico Display V1 and button A

import time
from pimoroni import Button
button_a = Button(12)

list = ["a","b","c","d","e","f","g","h"]

p = -1
while True:
    if button_a.read():
        p = (p + 1) % 8
        print(p,list[p])

Produces this:

MicroPython 99c2589 on 2022-07-07; Raspberry Pi Pico W with RP2040

Type "help()" for more information.
>>> %Run -c $EDITOR_CONTENT
0 a
1 b
2 c
3 d
4 e
5 f
6 g
7 h
0 a
1 b
2 c
3 d
4 e
5 f

Hope this is what you wanted.

#3

Thank you Tony for a very prompt response and I think this will get me where I want to be. Sorry if it seemed to be a “Noddy” problem but I am still learning Python and have been scratching my head over this for a few days. Thanks again!
Mick Farmer

#4

p = (p + 1) % 8

Huh, I’d made a mental note to reply to this and had an if p == 8, p = 0 loop in mind for the roll-over, but using % 8 is a super-elegant way to do that. You learn something every day!

#5

I only twigged this myself a couple of weeks ago while working on a Neopixel ring and I’ve been coding since 1968!
The beauty of it is that it works in both directions (+1 and -1).