n Python 3, if you are sure that :data:`n` can fit into
    :data:`blocksize` bytes, you can simply use the native method instead::

        >>> n.to_bytes(blocksize, 'big')

    For instance::

        >>> n = 80
        >>> n.to_bytes(2, 'big')
        b'\x00P'

    However, and unlike this ``long_to_bytes()`` function,
    an ``OverflowError`` exception is raised if :data:`n` does not fit.
r