bitfield.py

import math

class Bitfield:
    def __init__(self, size):
        self.size = size
        self.bytes = bytearray(math.ceil(size / 8))

    def __len__(self):
        return self.size

    def __getitem__(self, idx):
        return self.bytes[idx // 8] >> (idx % 8) & 1

    def __setitem__(self, idx, value):
        mask = 1 << (idx % 8)
        if value:
            self.bytes[idx // 8] |= mask
        else:
            self.bytes[idx // 8] &= ~mask