Random bytes generation in Python

randbytes.py

import random as random_mod


try:
    import ctypes

    _long_as_byte_array = ctypes.pythonapi._PyLong_AsByteArray
    _long_as_byte_array.argtypes = [
        ctypes.py_object,
        ctypes.POINTER(ctypes.c_char),
        ctypes.c_size_t,
        ctypes.c_int,
        ctypes.c_int
    ]

    def _long_to_bytes(num, size):
        buf = ctypes.create_string_buffer(size)
        _long_as_byte_array(num, buf, size, 0, 0)
        return buf.raw
except ImportError:
    import binascii

    def _long_to_bytes(num, size):
        return binascii.unhexlify(hex(num)[2: -1].zfill(2 * size))


def randbytes(size, random=None):
    if size < 1:
        return ''
    if random is None:
        random = random_mod
    return _long_to_bytes(random.getrandbits(8 * size), size)