accepts strings only for unpickling reasons.  This check prevents the honest
mistake of passing a string like '2:59.0' to time() and getting an insane
object.

the changes.

Treat comparing a date to a datetime like a mixed-type comparison.

New include file timefuncs.h exports private API function
_PyTime_DoubleToTimet() from timemodule.c.  timemodule should export
some other functions too (look for painful bits in datetimemodule.c).

Added insane-argument checking to datetime's assorted fromtimestamp()
and utcfromtimestamp() methods.  Added insane-argument tests of these
to test_datetime, and insane-argument tests for ctime(), localtime()
and gmtime() to test_time.

datetime.datetime and datetime.time could yield insane objects.  Thanks
to Jiwon Seo for the fix.

Bugfix candidate.  I'll backport it to 2.3.

It's possible to create insane datetime objects by using the constructor
"backdoor" inserted for fast unpickling.  Doing extensive range checking
would eliminate the backdoor's purpose (speed), but at least a little
checking can stop honest mistakes.

Bugfix candidate.

The interning of short strings violates the refcnt==1 assumption for
_PyString_Resize().

A simple fix is to boost the initial value of "totalnew" by 1.
Combined with an NULL argument to PyString_FromStringAndSize(),
this assures that resulting format string is not interned.
This will remain true even if the implementation of
PyString_FromStringAndSize() changes because only the uninitialized
strings that can be interned are those of zero length.

Added a test case.

one good use:  a subclass adding a method to express the duration as
a number of hours (or minutes, or whatever else you want to add).  The
native breakdown into days+seconds+us is often clumsy.  Incidentally
moved a large chunk of object-initialization code closer to the top of
the file, to avoid worse forward-reference trickery.

attributes and methods work, that new arguments can be passed to the
constructor, and that inherited methods and attrs still work.  Added
XXX comments about what to do when datetime becomes usably subclassable
too (it's not yet).

(This is only the tip of the iceberg; the time and datetime classes
need the same treatment.)

tickle the 2.2.2 __cmp__ bug test_datetime used to tickle, so the
workarounds for that bug no longer make sense in the test suite (which I'm
still trying to keep as closely in synch as possible with Zope3's
version).

__ne__ no longer complain if they don't know how to compare to the other
thing.  If no meaningful way to compare is known, saying "not equal" is
sensible.  This allows things like

    if adatetime in some_sequence:
and
    somedict[adatetime] = whatever

to work as expected even if some_sequence contains non-datetime objects,
or somedict non-datetime keys, because they only call __eq__.

It still complains (raises TypeError) for mixed-type comparisons in
contexts that require a total ordering, such as list.sort(), use as a
key in a BTree-based data structure, and cmp().

the tests will remain in sync:

"""
Tres discovered a weird bug when a datetime is pickled, caused by the
shadowing of __year, __month, __day and the use of proxies.

Here's a quick fix and a quick unit test.  I don't quite understand
why this wasn't caught by the pickling unit tests.
"""

Apparently MAC OS 9 doesn't have POSIX-conforming timestamps.  A test
fails as a result, but at least for this specific test it's easy enough
to get the POSIX epoch out of it.

cross-pickling tests.

anymore either, so don't.  This also allows to get rid of obscure code
making __getnewargs__ identical to __getstate__ (hmm ... hope there
wasn't more to this than I realize!).

longer needs to be public, and shoudn't be public because all datetime
objects are immutable.  The Python implementation has changed
accordingly, but still need to change the C implementation.

classes have a __reduce__ that returns (self.__class__,
self.__getstate__()).  tzinfo.__reduce__() is a bit smarter, calling
__getinitargs__ and __getstate__ if they exist, and falling back to
__dict__ if it exists and isn't empty.

compare against "the other" argument, we raise TypeError,
in order to prevent comparison from falling back to the
default (and worse than useless, in this case) comparison
by object address.

That's fine so far as it goes, but leaves no way for
another date/datetime object to make itself comparable
to our objects.  For example, it leaves Marc-Andre no way
to teach mxDateTime dates how to compare against Python
dates.

Discussion on Python-Dev raised a number of impractical
ideas, and the simple one implemented here:  when we don't
know how to compare against "the other" argument, we raise
TypeError *unless* the other object has a timetuple attr.
In that case, we return NotImplemented instead, and Python
will give the other object a shot at handling the
comparison then.

Note that comparisons of time and timedelta objects still
suffer the original problem, though.

This gives much the same treatment to datetime.fromtimestamp(stamp, tz) as
the last batch of checkins gave to datetime.now(tz):  do "the obvious"
thing with the tz argument instead of a senseless thing.

checked in two days agao:

Refactoring of, and new rules for, dt.astimezone(tz).

dt must be aware now, and tz.utcoffset() and tz.dst() must not return None.
The old dt.astimezone(None) no longer works to change an aware datetime
into a naive datetime; use dt.replace(tzinfo=None) instead.

The tzinfo base class now supplies a new fromutc(self, dt) method, and
datetime.astimezone(tz) invokes tz.fromutc().  The default implementation
of fromutc() reproduces the same results as the old astimezone()
implementation, but tzinfo subclasses can override fromutc() if the
default implementation isn't strong enough to get the correct results
in all cases (for example, this may be necessary if a tzinfo subclass
models a time zone whose "standard offset" (wrt UTC) changed in some
year(s), or in some variations of double-daylight time -- the creativity
of time zone politics can't be captured in a single default implementation).

When daylight time ends, an hour repeats on the local clock (for example,
in US Eastern, the clock jumps from 1:59 back to 1:00 again).  Times in
the repeated hour are ambiguous.  A tzinfo subclass that wants to play
with astimezone() needs to treat times in the repeated hour as being
standard time.  astimezone() previously required that such times be
treated as daylight time.  There seems no killer argument either way,
but Guido wants the standard-time version, and it does seem easier the
new way to code both American (local-time based) and European (UTC-based)
switch rules, and the astimezone() implementation is simpler.

hoped it would be, but not too bad.  A test had to change:
time.__setstate__() can no longer add a non-None tzinfo member to a time
object that didn't already have one, since storage for a tzinfo member
doesn't exist in that case.

into time.  This is little more than *exporting* the datetimetz object
under the name "datetime", and similarly for timetz.  A good implementation
of this change requires more work, but this is fully functional if you
don't stare too hard at the internals (e.g., right now a type named
"datetime" shows up as a base class of the type named "datetime").  The
docs also need extensive revision, not part of this checkin.

cases, plus even tougher tests of that.  This implementation follows
the correctness proof very closely, and should also be quicker (yes,
I wrote the proof before the code, and the code proves the proof <wink>).

(or None) now.  In 2.3a1 they could also return an int or long, but that
was an unhelpfully redundant leftover from an earlier version wherein
they couldn't return a timedelta.  TOOWTDI.

dst() returns None (instead of treating that as 0).

suggestion from Guido, along with a formal correctness proof of the
trickiest bit.  The intricacy of the proof reveals how delicate this
is, but also how robust the conclusion:  correctness doesn't rely on
dst() returning +- one hour (not all real time zones do!), it only
relies on:

1. That dst() returns a (any) non-zero value if and only if daylight
   time is in effect.

and

2. That the tzinfo subclass implements a consistent notion of time zone.

The meaning of "consistent" was a hidden assumption, which is now an
explicit requirement in the docs.  Alas, it's an unverifiable (by the
datetime implementation) requirement, but so it goes.

understood now:  it can't work.  Added comments explaining why (it's "the
usual"-- unrepresentable hours in local time --but in a slightly different
guise).

an idea from Guido.  This restores that the datetime implementation
never passes a datetime d to a tzinfo method unless d.tzinfo is the
tzinfo instance whose method is being called.  That in turn allows
enormous simplifications in user-written tzinfo classes (see the Python
sandbox US.py and EU.py for fully fleshed-out examples).

d.astimezone(tz) also raises ValueError now if d lands in the one hour
of the year that can't be expressed in tz (this can happen iff tz models
both standard and daylight time).  That it used to return a nonsense
result always ate at me, and it turned out that it seemed impossible to
force a consistent nonsense result under the new implementation (which
doesn't know anything about how tzinfo classes implement their methods --
it can only infer properties indirectly).  Guido doesn't like this --
expect it to change.

New tests of conversion between adjacent DST-aware timezones don't pass
yet, and are commented out.

Running the datetime tests in a loop under a debug build leaks 9
references per test run, but I don't believe the datetime code is the
cause (it didn't leak the last time I changed the C code, and the leak
is the same if I disable all the tests that invoke the only function
that changed here).  I'll pursue that next.

of the timetz case.  A tzinfo method will always see a datetimetz arg,
or None, now.  In the former case, it's still possible that it will get
a datetimetz argument belonging to a different timezone.  That will get
fixed next.

and that conversion to "timezone" None is the same as stripping the
tzinfo member.

west of the US zones getting converted, and also by using Eastern "as if"
it were UTC (wrt Pacific), and vice versa.

Guido has in mind an easier way for users to code this stuff, but the
only tests we have now are for fixed-offset tzinfo classes, and this
stuff is extremely delicate in the endcases (read the new test code
for why:  there are holes in time <wink>).