For example, if I have a unicode string, I can encode it as an ASCII string like so:
>>> u\'\\u003cfoo/\\u003e\'.encode(\'ascii\')
It took me a while to figure this one out, but this page had the best answer:
>>> s = '\u003cfoo/\u003e'
>>> s.decode( 'unicode-escape' )
u' '
>>> s.decode( 'unicode-escape' ).encode( 'ascii' )
' '
There's also a 'raw-unicode-escape' codec to handle the other way to specify Unicode strings -- check the "Unicode Constructors" section of the linked page for more details (since I'm not that Unicode-saavy).
EDIT: See also Python Standard Encodings.