gistfile1.py

def bitstruct(structure, value):
    result = []
    index = 8
    for part in structure:
        result.append((value & ((2 ** index - 1) - (2 ** (index - part) - 1))) >> (index - part))
        index -= part
    return tuple(result)

if __name__ == "__main__":
    assert bitstruct((8, ), 42) == (42, )
    assert bitstruct((1, ), 128) == (1, )
    assert bitstruct((1, ), 64) == (0, )
    assert bitstruct((1, 1), 64) == (0, 1)
    assert bitstruct((4, 4), 127) == (7, 15)