"Are you worried that Python 2.2 will break all your
old Python code? Don't be! Help us make Python 2.2 as compatible
and stable as any release before it. I've released the first alpha
release, Python 2.2a1, for your perusal.
New features in this release include:
TENTATIVELY, a new way of introspecting instances of
built-in types (PEP 252) and the ability to subclass built-in types
(PEP 253) have been added. This falls under the header of
"type/class unification". More about this below.
Iterators (PEP 234) and generators (PEP 255) were added. The
second PEP adds a new reserved word, "yield", which must be enabled
by adding "from __future__ import generators" to the top of every
module that uses it. Without that, "yield" is treated as an
identifier but a warning is issued."