transform list of integers into bitmaps bytes and back

list_to_bitmaps.py

import numpy as np

ids = [1, 5, 7, 12]
bitmaps = np.zeros(max(ids) + 1, dtype=np.bool)
bitmaps[ids] = True
bitmaps = np.packbits(bitmaps).tostring()
print(bitmaps)
# b'E\x08'
# could be use as a binary field to be stored in database

origin_ids = np.where(
    np.unpackbits(
        np.frombuffer(bitmaps,
                      dtype=np.uint8)))[0].tolist()
print(origin_ids)
# [1, 5, 7, 12]