.encrypt(b)

is equivalent to:

     >>> c.encrypt(a+b)

That also means that you cannot reuse an object for encrypting
or decrypting other data with the same key.

This function does not add any padding to the plaintext.

:Parameters:
  plaintext : bytes/bytearray/memoryview
    The piece of data to encrypt.
    Its lenght must be multiple of the cipher block size.
:Keywords:
  output : bytearray/memoryview
    The location where the ciphertext must be written to.
    If ``None``, the ciphertext is returned.
:Return:
  If ``output`` is ``None``, the ciphertext is returned as ``bytes``.
  Otherwise, ``None``.
r