It seems to be working consistently (see UTF-16 extreme example below),
but I had expected it to act similarly to Python 2.6, which it does not.
I suppose this is due to the distinction now made between strings and
bytes in Python 3.0.

I was initially concerned that Python 3.0 was always just giving an
ASCII byte stream no matter what encoding was chosen (since you can't
tell between ASCII and UTF-8 for the characters being used in the
example), but the UTF-16 example shows its fine.

I agree that as long as the documentation in Python 3.X notes it will
return "bytes", then its fine. Thanks for the clarification/confirmation.

Python 3.0 (r30:67507, Dec  3 2008, 20:14:27) [MSC v.1500 32 bit
(Intel)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import calendar
>>> calendar.HTMLCalendar().formatyearpage(2009, encoding="utf-8")[0:50]
b'<?xml version="1.0" encoding="utf-8"?>\n<!DOCTYPE h'
>>> calendar.HTMLCalendar().formatyearpage(2009, encoding="ascii")[0:50]
b'<?xml version="1.0" encoding="ascii"?>\n<!DOCTYPE h'
>>> calendar.HTMLCalendar().formatyearpage(2009, encoding="utf-16")[0:50]
b'\xff\xfe<\x00?\x00x\x00m\x00l\x00
\x00v\x00e\x00r\x00s\x00i\x00o\x00n\x00=\x00"\x001\x00.\x000\x00"\x00
\x00e\x00n\x00c\x00o\x00'

Python 2.6.1 (r261:67517, Dec  4 2008, 16:51:00) [MSC v.1500 32 bit
(Intel)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import calendar
>>> calendar.HTMLCalendar().formatyearpage(2009, encoding="utf-8")[0:50]
'<?xml version="1.0" encoding="utf-8"?>\n<!DOCTYPE h'
>>> calendar.HTMLCalendar().formatyearpage(2009, encoding="ascii")[0:50]
'<?xml version="1.0" encoding="ascii"?>\n<!DOCTYPE h'
>>> calendar.HTMLCalendar().formatyearpage(2009, encoding="utf-16")[0:50]
'\xff\xfe<\x00?\x00x\x00m\x00l\x00
\x00v\x00e\x00r\x00s\x00i\x00o\x00n\x00=\x00"\x001\x00.\x000\x00"\x00
\x00e\x00n\x00c\x00o\x00'