Binary Sort on Python List __xor__

[evan.schalton at gmail.com]

I frequently use binary as bool placeholders and find myself filtering lists based on those bools, this seems to have a similar semantic meaning as the bit wise ^ or __xor__ operator and could add syntactic sugar to the base list class.

Use Case:

Controlling a stepper at half-step has the following cycle steps:

CYCLE = [
  [1,0,0,0],
  [1,1,0,0],
  [0,1,0,0],
  [0,1,1,0],
  [0,0,1,0],
  [0,0,1,1],
  [0,0,0,1],
  [1,0,0,1],
]

which can be represented as follows:

CYCLE = [
    1<<3,
    1<<3|1<<2,
    1<<2,
    1<<2|1<<1,
    1<<1,
    1<<1|1<<0,
    1<<0,
    1<<3|1<<0
]

or more cleanly:

CYCLE = [8, 12, 4, 6, 2, 3, 1, 9]

on a raspberrypi, using (for illustration's sake) GPIO pins 1,2,3,4 I'd like to use the __xor__ method (currently not implemented) to perform the bit-wise filter as follows:

class MyList(list):
    def __init__(self, *args):
        super().__init__(args)
    
    def __xor__(self, num):
        return [self[i] for i in [-index-1 for index, i in enumerate(bin(num)[:1:-1]) if i !='0']][::-1]

PINS = MyList(1,2,3,4)

PINS ^ 8
# [1]

PINS ^ 12
# [1, 2]

PINS ^ 4
# [2]

PINS ^ 6
# [2, 3]

PINS ^ 2
# [3]

PINS ^ 3
# [3, 4]

PINS ^ 1
# [4]

PINS ^ 9
# [1, 4]

The need here isn't strictly pi/stepper related; I've run into this several times in the past when evaluating combinations * permutations of items where a bitwise filter would be useful.