randnum.py 文件源码

def read_random_bits(nbits):
    '''Reads 'nbits' random bits.

    If nbits isn't a whole number of bytes, an extra byte will be appended with
    only the lower bits set.
    '''

    nbytes, rbits = divmod(nbits, 8)

    # Get the random bytes
    randomdata = os.urandom(nbytes)

    # Add the remaining random bits
    if rbits > 0:
        randomvalue = ord(os.urandom(1))
        randomvalue >>= (8 - rbits)
        randomdata = byte(randomvalue) + randomdata

    return randomdata