An example usage of an encryption algorithm (AES, in this case) is:

>>> from Crypto.Cipher import AES

>>> obj = AES.new('This is a key123', AES.MODE_CBC, 'This is an IV456')

>>> message = "The answer is no"

>>> ciphertext = obj.encrypt(message)

>>> ciphertext

'\xd6\x83\x8dd!VT\x92\xaa`A\x05\xe0\x9b\x8b\xf1'

>>> obj2 = AES.new('This is a key123', AES.MODE_CBC, 'This is an IV456')

>>> obj2.decrypt(ciphertext)

'The answer is no'