Just copying some details here about codecs.encode() and
codec.decode() from python-dev:

"""
Just as reminder: we have the general purpose
encode()/decode() functions in the codecs module:

import codecs
r13 = codecs.encode('hello world', 'rot-13')

These interface directly to the codec interfaces, without
enforcing type restrictions. The codec defines the supported
input and output types.
"""

As Nick found, these aren't documented, which is a documentation
bug (I probably forgot to add documentation back then).
They have been in Python since 2004:

http://hg.python.org/cpython-fullhistory/rev/8ea2cb1ec598

These API are nice for general purpose codec work and
that's why I added them back in 2004.

For the codecs in question, it would still be nice to have
a more direct way to access them via methods on the types
that you typically use them with.