What's New in Python 2.2.3 (final) ?
Release date: 30-May-2003
====================================

- SF #745055: Fix memory leaks in Tkapp_Split and Tkapp_SplitList.

- On Posix systems, as of Python 2.2, the arguments for
  socket.socket() default to AF_INET, SOCK_STREAM.  This is now so for
  the Windows-specific wrapper in socket.py as well.

- Backport SF #736892: Add argument sanity checking for __get__().

- SF #742911: Fix segfault due to clearing weak references too late
  for new-style class instances.

- Backport SF 742860: new, improved __delitem__ for WeakKeyDictionary.
  The old __delitem__ wasn't threadsafe, was very inefficient (expected
  time O(len(dict)) instead of O(1)), and could raise a spurious
  RuntimeError if another thread mutated the dict during __delitem__, or if
  a comparison function mutated it.  It also neglected to raise KeyError
  when the key wasn't present; didn't raise TypeError when the key wasn't
  of a weakly referencable type; and broke various more-or-less obscure
  dict invariants by using a sequence of equality comparisons over the
  whole set of dict keys instead of computing the key's hash code to
  narrow the search to those keys with the same hash code.  All of these
  are considered to be bugs.  A new implementation of __delitem__ repairs
  all that, but note that fixing these bugs may change visible behavior
  in code relying (whether intentionally or accidentally) on old behavior.

- Backport SF #745478: email package 2.5.3; fixes a buglet in
  multipart boundary calculation.

- RPM spec file update from Sean Reifschneider.

- Mac OS X specific backports for distutils/unixccompiler.py.  SF #723495


What's New in Python 2.2.3c1 ?
Release date: 22-May-2003
============================

- C API:  PyType_Ready():  If a type declares that it participates in gc
  (Py_TPFLAGS_HAVE_GC), and its base class does not, and its base class's
  tp_free slot is the default _PyObject_Del, and type does not define
  a tp_free slot itself, _PyObject_GC_Del is assigned to type->tp_free.
  Previously _PyObject_Del was inherited, which could at best lead to a
  segfault.  In addition, if even after this magic the type's tp_free
  slot is _PyObject_Del or NULL, and the type is a base type
  (Py_TPFLAGS_BASETYPE), TypeError is raised:  since the type is a base
  type, its dealloc function must call type->tp_free, and since the type
  is gc'able, tp_free must not be NULL or _PyObject_Del.

- Windows:  file.truncate(size) failed on large files when size didn't
  fit in 32 bits.  This was fixed by backporting new Windows truncation
  code and tests from 2.3.

- It is no longer possible to use object.__setattr__ to circumvent the
  restrictions on setting attributes of type objects.

- Implemented os.fsync() for Windows, where it calls the MS _commit()
  function.  Before, there was no way in core Python to ensure file
  writes actually showed up on disk when necessary.

- Make all the strip, lstrip, rstrip functions/methods on
  string/unicode/UserString consistent by adding and/or
  documenting the chars parameter.  The chars parameter
  specifies which characters to strip.

- Some horridly obscure problems were fixed involving interaction
  between garbage collection and classes with "ambitious" getattr hooks.
  If a class instance didn't have a __del__ method, but did have a
  __getattr__ hook, and the instance became reachable only from an
  unreachable cycle, and the hook resurrected or deleted unreachable
  objects when asked to resolve "__del__", anything up to a segfault
  could happen.  That's been repaired.

- Skip locale test on Mac OS X.

- Fixed some build problems related to Redhat Linux 9.

- Backported the "largefile" requirement for test_largefile on Mac OS X.

- Backported email package 2.5.2, which makes address parsing slightly
  more robust.

- Added new encodings for Ukrainian Cyrillic.

- SF #710576: Backport of fix for #663074, to implement per-interpreter
  codecs registries. This adds new members at the end of
  PyInterpreterState.

- SF #705836: The platform-independent routines for packing floats in
  IEEE formats (struct.pack's f, d codes; pickle and
  cPickle's protocol 1 pickling of floats) ignored that rounding can
  cause a carry to propagate.  The worst consequence was that, in rare
  cases, f could produce strings that, when unpacked again,
  were a factor of 2 away from the original float.  This has been
  fixed.

- SF #645777: list.extend() works with any iterable and is no longer
  experimental.

- Backported SF patch #676342: after using pdb, the readline command
  completion was botched.  Backport fix for SF bug #741171, pdb
  crashes when enabling a non-existent breakpoint.

- Fix problem building on OSF1 because the compiler only accepted
  preprocessor directives that start in column 1.  (SF bug #691793.)

- Fixed two places in PyObject_Generic{Get,Set}Attr() where the
  tp_descr_{get,set} slot of a descriptor's type was accessed without
  checking tp_flags whether those slots actually exist.  This could
  cause segfaults in Zope.

- The imp module now has ways to acquire and release the "import
  lock": imp.acquire_lock() and imp.release_lock().  Note: this is a
  reentrant lock, so releasing the lock only truly releases it when
  this is the last release_lock() call.  You can check with
  imp.lock_held().  (SF bug #580952 and patch #683257.)

- Through a bytecode optimizer bug (and I bet you didn't even know
  Python *had* a bytecode optimizer :-), "unsigned" hex/oct constants
  with a leading minus sign would come out with the wrong sign.
  ("Unsigned" hex/oct constants are those with a face value in the
  range sys.maxint+1 through sys.maxint*2+1, inclusive; these have
  always been interpreted as negative numbers through sign folding.)
  E.g. 0xffffffff is -1, and -(0xffffffff) is 1, but -0xffffffff would
  come out as -4294967295.  This was the case in Python 2.2 through
  2.2.2 and 2.3a1, and in Python 2.4 it will once again have that
  value, but according to PEP 237 it really needs to be 1 in Python
  2.2.3 and 2.3.  (SF #660455)

- SF bug #678518:  fix some bugs in the parser module.

- Bastion.py and rexec.py are disabled.  These modules are not safe in
  Python 2.2. or 2.3.

- SF #676155: fixed errors when trying to convert a long integer
  into a float which couldn't fit.

- SF #660476 and #513033: broken threadstate swap in readline could
  cause fatal errors when a readline hook was being invoked while a
  background thread was active.

- SF #623669: a class that inherits __rdiv__ (or another __r*__
  operator) could end up with infinite recursion.

- Fixed sundry memory leaks.

- More objects participate in garbage collection: classmethod,
  staticmethod, and cPickle Pickler and Unpickler. (SF #735247)

- Improve the robustness of the methods for random distributions so
  they can work with generators producing a full range of values
  (unlike the Wichmann-Hill generator which never produces a zero).
  The range of u=random() is [0,1), so log(u) and 1/x can fail.  Fix
  by setting u=1-random() or by reselecting for a usable value.

- SF #659709: bogus float length computation during string formatting.

- Deleted the __del__ method on socket wrappers; it's not needed and
  prevents GC to work.

- Exceptions raised by __cmp__ weren't always properly handled and
  could cause "exception set without error return" failures.

- Fixed an old bug in asyncore.py which could cause bogus read calls
  on file descriptors after a signal is handled while blocked in
  select().

- SF #643260: __rpow__ wasn't being called.

- SF #534748, #645383: in setup.py, when modules fail to import, don't
  just delete them.

- SF #529750: _Py_ResetReferences() is now a no-op.

- SF #505427: build problem on HP-UX (h_errno not defined).

- SF #564729: make FixTk.py search properly for Tix subdirectories.

- Made string.strip() work as documented.

- Implemented some additional restrictions on __class__ assignment.

- SF #630824: added keyword 'yield' to pydoc.py.

- SF #626172: fix crash using Unicode Latin-1 single character.

- SF #570655: fix misleading option text in distutils rpm creation.

- SF #624982: fix potential segfault in slot_sq_item.

- New codec for Ukrainian Cyrillic.

- SF #665913: fix crash on Solaris when closing an mmap'ed file which
  was already closed.

- SF #639945: fix crash on 64-bit AIX when loading dynamic modules.

- SF #659228, fix realpath() not being exported from os.path

- SF #667147, fix crash when printing str subclass.

- SF #557719, backported just the tiny fragment necessary to get BUILDEXE
  set properly in out-of-tree builds.

- SF #649762, fix infinite loop in asynchat when null string used as terminator

- SF #570655, fix misleading option text for bdist_rpm

- Distutils: Allow unknown keyword arguments to the setup() function
  and the Extension constructor, printing a warning about them instead
  of reporting an error and stopping.

- Distutils: Translate spaces in the machine name to underscores
  (Power Macintosh -> Power_Macintosh)

- Distutils: on Mac OS X don't use -R for runtime_library_dirs, use
  -L in stead (#723495).

- Backported SF #658233, continuation lines in .mo file metadata
  crashed gettext.GNUTranslations parsing.  Also, export more symbols
  in the gettext module's __all__.

- Other patch and bug fix backports: 734869, 497420, 728322, 730963,
  723831, 708604, 723136, 549141, 557704, 724751, 716969, 711835,
  697220, 710498, 706338, 659834, 695250, 672614, 707701, 698517,
  709428, 708201, 700798, 703471, 676990, 521782, 635570, 633359,
  610299, 491107, 687655, 684667, 642168, 682514, 675259, 654974,
  655271, 641111, 642742, 669553, 634866, 664183, 664044, 665570,
  430610, 427345, 658106, 643227, 649095, 646578, 637941, 639170,
  635929, 637807, 637810, 424106, 635595, 613605, 635656, 633560,
  632864, 618146, 632196, 616211, 577000, 546579, 626554, 606463,
  217195


What's New in Python 2.2.2 (final) ?
Release date: 14-Oct-2002
====================================

Almost everything in this release is a pure bugfix and is backported
from a corresponding bugfix already applied to Python 2.3.  While at
the time of writing, Python 2.3 is still in pre-alpha form, only
accessible via CVS, it receives continuous and extensive testing by
its developers.  The list below is not a complete list of fixed bugs;
it only lists fixed bugs that someone might be interested in hearing
about.  Documentation fixes are not listed.

Tip: to quickly find SourceForge bug or patch NNNNNN, use an URL of
the form www.python.org/sf/NNNNNN.

Here are all the changes since the 2.2.2b1 release last week, except
for documentation changes.  Below it are the (much more numerous!)
changes since the 2.2.1 release in April.

Core and builtins

- In listobject.c and tupleobject.c: added overflow checks for
  list*int, list+list, and tuple+tuple.

- In object.c: changed misleading SystemError exceptions raised in
  PyObject_Init() and PyObject_InitVar() to MemoryError.

- In stringobject.c: added an overflow check to string formatting;
  this example could segfault: '%2147483647d' % -1.  [SF bug 618623]

- In typeobject.c: removed COPYSLOT(tp_dictoffset) from
  inherit_slots().  For more info, read this python-dev thread:
  http://mail.python.org/pipermail/python-dev/2002-October/029502.html

- In stringobject.c: fixed another string formatting nit: "%r" % u"..."
  would return a Unicode string, even though repr(u"...")  returns an
  8-bit string.  Now "%r" also returns an 8-bit string.

- In pystate.c: initialize the tick_counter to zero.

Library

- This release includes the email package version 2.4.3, which fixes
  some minor bugs found in email 2.4.1 since its release.

- In urlparse.py: a one-character fix to urlunsplit() caused breakage
  when parsing relative URLs, so added a fix for the fix and a test
  for the fix.  [SF bug 620705]

- In re.py: the finditer() function was accidentally not defined.  [SF
  bug 585882]

- In webbrowser.py: fixed Konqueror support.  [SF patch 539360]

- In xml/sax/expatreader.py: fixed a bug in the expat-based SAX reader
  that allows it to work with arbitrary versions of Expat.

- In distutils/sysconfig.py: added a no-op version of
  set_python_build() back, to avoid breaking code that might call
  this.  (It remains no longer needed and hence deprecated, though.)

Build

- In configure[.in]: expand AC_CHECK_SIZEOF inline to overcome a
  autoconf 2.13 weakness.  [SF bug 620791]

- In setup.py: Be more conservative about adding a -R flag for the SSL
  code; it is needed on Solaris 8 and broke on Mac OSX 10.2.  The -R
  flag is now only added for Solaris.

Tests

- The test list(xrange(sys.maxint / 4)) test in test_b1.py was changed
  to use sys.maxint / 2 instead.  This means that the test will not
  attempt to allocate any memory, but merely check that the overflow
  detection code works correctly (as was intended).

- The MacOSX (both 10.1 and 10.2) tests will crash with SEGV in
  test_re and test_sre due to the small default stack size.  If you
  set the stack size to 2048 before doing a "make test" the failure
  can be avoided.  If you're using the tcsh (the default on OSX), or
  csh shells use "limit stacksize 2048" and for the bash shell, use
  "ulimit -s 2048".

Windows

- Fixed the "File version" field in the DLL.  This has apparently been
  broken forever.

Other

- Updated the Misc/ACKS file to acknowledge many new contributors.


What's New in Python 2.2.2b1?
Release date: 7-Oct-2002
=============================

Core and builtins

- Changed new-style class instantiation so that when C's __new__
  method returns something that's not a C instance, its __init__ is
  not called.  [SF bug #537450]  (This is arguably a semantic change,
  but it's hard to imagine a reason for wanting to depend on the old
  behavior.  If problems with this are reported within a week of the
  release of 2.2.2 beta 1, we may revert this change.)

- Fix a core dump in type_new() when looking for the tp_init() slot.
  This could call a garbage pointer when e.g. an ExtensionClass was
  given.

- A variety of very obscure end-case bugs in new-style classes were
  fixed, some of which could be made to trigger core dumps with absurd
  input.

- u'%c' will now raise a ValueError in case the argument is an
  integer outside the valid range of Unicode code point ordinals.

- Several small patches were applied that aren't bugfixes (and aren't
  even backported from 2.3!) but make life easier for tools like Armin
  Rigo's Psyco.  [SF patches 617309, 617311, 617312]

- Made conversion failure error message consistent between types.

- The complex() built-in now finds __complex__() in new-style
  classes.  [SF bug 563740]

- Fixed a problem in the UTF-8 decoder where a Unicode literal
  containing a "lone surrogate" would cause a .pyc file to be written
  that could not be read.  [SF bug 610783]

- Fixed a problem with code objects whose stacksize is >= 2**15.
  These cannot be marshalled correctly.  As a work-around, don't write
  a .pyc file in this case.  [SF bug 561858]

- Fixed several bugs that could cause issubclass() and isinstance() to
  leave an exception lingering behind while returning a non-error
  value.

- The Unicode replace() method would do the wrong thing for a unicode
  subclass when there were zero string replacements.  [SF bug 599128]

- Fixed some endcase bugs in Unicode rfind()/rindex() and endswith().
  [SF bug 595350]

- When x is an object whose class implements __mul__ and __rmul__,
  1.0*x would correctly invoke __rmul__, but 1*x would erroneously
  invoke __mul__.  This was due to the sequence-repeat code in the int
  type.  This has been fixed now.

- The __delete__ method wrapper wasn't supported.  [SF patch 588728]

- If a dying instance of a new-style class got resurrected by its
  class's __del__ method, Python aborted with a fatal error.

- Source that creates parse nodes with an extremely large number of
  children (e.g.,  test_longexp.py) triggers problems with the
  platform realloc() under several platforms (e.g., MacPython, and
  Win98).  This has been fixed via a more-aggressive overallocation
  strategy.

- Fixed a bug with a continue inside a try block and a yield in the
  finally clause.  [SF bug 567538]

- Cycles going through the __class__ link of a new-style instance are
  now detected by the garbage collector.

- Classes using __slots__ are now properly garbage collected.
  [SF bug 519621]

- Fixed an inefficiency in clearing the stack frame of new frame
  objects.

- Repaired a slow memory leak possible only in programs creating a
  great many cyclic structures involving frames [SF bug 543148].

- Fixed an esoteric performance glitch in GC.  [SF bug 574132]

- A method zfill() was added to str and unicode, that fills a numeric
  string to the left with zeros.  For example,
  "+123".zfill(6) -> "+00123".

- Complex numbers supported divmod() and the // and % operators, but
  these make no sense.  Since this was documented, they're being
  deprecated now.

- String and Unicode methods lstrip(), rstrip() and strip() now take
  an optional argument that specifies the characters to strip.  For
  example, "Foo!!!?!?!?".rstrip("?!") -> "Foo". In addition,
  "200L".strip("L") will return "200". This is useful for replacing
  code that assumed longs will always be printed with a trailing "L".

- A change to how new-style classes deal with __doc__: you can now
  supply a __doc__ descriptor that returns something different for a
  class than for instances of that class.

- Fixed bug #521782: when a file was in non-blocking mode, file.read()
  could silently lose data or wrongly throw an unknown error.

Extension modules

- In readline.c: change completion to avoid appending a space
  character; this is usually more useful when editing Python code.

- Fixed a crash in debug builds for marshal.dumps([128] * 1000).  [SF
  bug 588452]

- In cPickle.c: more robust test of whether global objects are
  accessible.  Added recursion limit to pickling [SF bug 576084].  Try
  the persistent id code *before* calling save_global().

- In mmapmodule.c: if the size passed to mmap() is larger than the
  length of the file on non-Windows platforms, a ValueError is
  raised. [SF bug 585792]

- In socketmodule.c: improve robustness of IPv6 code.

- In _hotshot.c: fix broken logic in the logreader object.

- In zlibmodule.c: fix for crash on second flush() call.  [SF bug
  544995]

Library

- The email package from the Python 2.3 development tree has been
  backported, including updated documentation.  This version
  corresponds to email 2.4.1 and should be nearly completely backward
  compatible.  However there have been lots of improvements in the
  API, so you should read the section in the library manual about the
  changes since email v1.

- In pydoc.py: Extend stripid() to handle strings ending in more than
  one '>'; add resolve() to handle looking up objects and names (fix
  SF bug 586931); add a nicer error message when given a filename that
  doesn't exist.  Pretend that the docstring for non-callable objects
  is always None; this makes for less confusing output and fixes the
  problem reported in SF patch 550290.  Change the way 'less' is
  invoked as a browser (on Unix) to make it more robust.

- In pickle.py: whichmodule() now skips dummy (None) package entries
  in sys.modules.  Try the persistent id code *before* calling
  save_global().

- A variety of fixes were applied to the compiler package.

- In distutils/: Fix distutils.sysconfig to understand that the
  running Python is part of the build tree and needs to use the
  appropriate "shape" of the tree [SF patch 547734].  Prefer rpmbuild
  over rpm if available [SF patch 619493].   util.convert_path()
  failed with empty pathname.  [SF bug 574235]

- In posixpath.py and user.py: fixed SF bug 555779, "import user
  doesn't work with CGIs."

- In site.py: fixed a problem which triggered when sys.path was empty.

- In smtpd.py: print the refused list to the DEBUGSTREAM [SF 515021];
  removed an embarrassing debug line from smtp_RCPT().

- In smtplib.py: fix multiline string in sendmail example [SF patch
  586999]; handle empty addresses [SF bug 602029].

- In urllib.py: treat file://localhost/ as local too (same as file:/
  and file:///).  [SF bug 607789]

- In warnings.py: ignore IOError when writing the message.

- In ConfigParser.py: allow internal whitespace in keys [SF bug
  583248]; use option name transform consistently in has_option() [SF
  bug 561822]; misc other patches.

- In sre_compile.py (the compile() function for the re module):
  Disable big charsets in UCS-4 builds. [SF bug 599377]

- In pre.py (the deprecated, *old* implementation of the re module):
  fix broken sub() and subn().  [SF bug 570057]

- In weakref.py: The WeakKeyDictionary constructor didn't work when a
  dict arg was given.  [SF patch 564549]

- In xml/: various fixes tracking PyXML.

- In urllib2.py: fix proxy config with user+pass authentication.  [SF
  patch 527518]

- In pdb.py: Increase the maxstring value of _saferepr.  Add exit as
  an alias for quit [SF bug 543674].  Fix crash on input line
  consisting of one or more spaces [SF bug 579701].

- In test/regrtest.py: added some sys.stdout.flush() calls.

- In random.py:

  - Deprecate (in comment) cunifvariate().  [SF bug 506647]

  - Loosened the acceptable 'start' and 'stop' arguments to
    randrange() so that any Python (bounded) ints can be used.  So,
    e.g., randrange(-sys.maxint-1, sys.maxint) no longer blows up.
    [SF bug 594996]

  - The gauss() method uses a piece of hidden state used by nothing
    else, and the .seed() and .whseed() methods failed to reset it.
    In other words, setting the seed didn't completely determine the
    sequence of results produced by random.gauss().  It does now.
    Programs repeatedly mixing calls to a seed method with calls to
    gauss() may see different results now.

  - The randint() method is rehabilitated (i.e. no longer deprecated).

-  In copy.py: when an object is copied through its __reduce__ method,
   there was no check for a __setstate__ method on the result [SF
   patch 565085]; deepcopy should treat instances of custom
   metaclasses the same way it treats instances of type 'type' [SF
   patch 560794].

- In turtle.py: update canvas before computing width; draw turtle when
  done drawing circle.  [SF bug 612595]

- In Tkinter.py: Canvas.select_item() now returns the selected item,
  if any.  [SF patch 581396]

- In multifile.py: *backed out* the change that stripped a trailing
  \r\n.  This caused more problems than it fixed.  [SF bug 514676]

- In rexec.py: fixed several security problems.  *This does not mean
  that rexec is now considered safe!*

- In os.py: security fixes for _execvpe().

- In gzip.py: open files in binary mode.

- In CGIHTTPServer.py: update os.environ regardless of hos it tries to
  handle calls (fork, popen*, etc.).  Also fixed a flush() of a
  read-only file (can't do that on MacOS X).

- In urllib.py: in splituser(), allow @ in the userinfo field.  This
  is not allowed by RFC 2396; however, other tools support unescaped
  @'s so we should also.  [SF patch 596581, bug 581529]

- In base64.py: decodestring('') should return '' instead of raising
  an exception.  [SF bug 595671]

- atexit.py: keep working if sys.exitfunc is already set when this is
  first imported.

- In copy.py: Make sure that *any* object whose id() is used as a memo
  key is kept alive in the memo.  [SF bug 592567]

- In httplib.py: fixed a variety of bugs.  The httplib.py in Python
  2.2.2 is identical to that in the CVS head (at the time of the
  release of 2.2.2).

- In rfc822.py: change the default for Message.get() back to None.

- In bdb.py: fix an old bug that made it impossible to continue after
  hitting a breakpoint while in the bottom frame.

- In Queue.py: use try/finally to ensure that all locks are properly
  released.  [SF bug 544473]

- In SocketServer.py: the correct initialization of self.wfile is
  StringIO.StringIO(), not StringIO.StringIO(self.packet).  [SF bug
  543318]

Build

- Various platform-specific problems were fixed, including most open
  64-bit platform specific issues.

- Updated Misc/RPM for Python 2.2.2b1; added Makefile.pre.in to -devel.

- The fpectl module is not built by default; it's dangerous or useless
  except in the hands of experts.  (At the same time, a fix for DEC
  Alpha under Linux was applied.)

- Better check for C++ linkage.  [SF bug 559429]

- The errno module needs to be statically linked, since it is now
  needed during the extension building phase.

- A bug was fixed that could cause COUNT_ALLOCS builds to segfault, or
  get into infinite loops, when a new-style class got garbage-collected.
  Unfortunately, to avoid this, the way COUNT_ALLOCS works requires
  that new-style classes be immortal in COUNT_ALLOCS builds.  Note that
  COUNT_ALLOCS is not enabled by default, in either release or debug
  builds, and that new-style classes are immortal only in COUNT_ALLOCS
  builds.  [SF bug 578752]

- In order to avoid problems with binutils 2.12 and later, test for
  --export-dynamic in its help output.

C API

- New C API PyUnicode_FromOrdinal() which exposes unichr() at C
  level.

Windows

- Improve handling of ^C on Windows.  [SF bug 439992]

- Provide a fallback version of ntpath.abspath() when the nt module
  can't be imported.

- Fixed asyncore on Windows to avoid calling select() with three empty
  lists.  Use time.sleep() instead, to match what happens on
  Unix/Linux in that case.  [SF item 611464]

- Fixed selectmodule.c to call WSAGetLastError() to retrieve the error
  number.

- Fixed the test for mmap so that it passes on Windows too.

- SF bug 595919:  popenN return only text mode pipes
  popen2() and popen3() created text-mode pipes even when binary mode
  was asked for.  This was specific to Windows.

- Sometimes the uninstall executable (UNWISE.EXE) vanishes.  One cause
  of that has been fixed in the installer (disabled Wise's "delete in-
  use files" uninstall option).

Other

- Most changes to IDLE were backported, including some featurettes.
  Open module can now handle hierarchical names for packages (such
  as xml.dom.minidom).  On Windows, Edit SelectAll is now called
  with Control-A rather than Alt-A.  The Edit Menu only offers
  module options (like import module, check module, or run script)
  in a module window.  Those options no longer appear in the shell
  window where they did not have meaningful application and was
  confusing new users.


What's New in Python 2.2.1 final?
Release date: 10-Apr-2002
=================================

Core and builtins

- Added new builtin function bool() and new builtin constants True and
  False to ease backporting of code developed for Python 2.3.  In 2.2,
  bool() returns 1 or 0, True == 1, and False == 0.

- Fixed super() to work correctly with class methods.  [SF bug #535444]

- Fixed two bugs reported as SF #535905: under certain conditions,
  deallocating a deeply nested structure could cause a segfault in the
  garbage collector, due to interaction with the "trashcan" code;
  access to the current frame during destruction of a local variable
  could access a pointer to freed memory.

Library

- The xml.sax.expatreader.ExpatParser class will no longer create
  circular references by using itself as the locator that gets passed
  to the content handler implementation.  [SF bug #535474]

C API

- A type can now inherit its metatype from its base type.  Previously,
  when PyType_Ready() was called, if ob_type was found to be NULL, it
  was always set to &PyType_Type; now it is set to base->ob_type,
  where base is tp_base, defaulting to &PyObject_Type.

- PyType_Ready() accidentally did not inherit tp_is_gc; now it does.

Windows

- Fixed a bug in urllib's proxy handling in Windows.  [SF bug #503031]

- The installer now installs Start menu shortcuts under (the local
  equivalent of) "All Users" when doing an Admin install.


What's New in Python 2.2.1c2?
Release date: 26-Mar-2002
=============================

There were a bunch of mostly minor fixes between 2.2.1c1 and 2.2.1c2,
including:

- I remembered to run autoconf before cutting the release tarball.

Core and builtins

- The floating point behavior fix-up continued into complex_pow.

Library

- The email package bug #531966 was fixed.  This caused exceptions to
  occur when flattening multipart/* messages with zero or one (scalar)
  attachment.

- Support for https: urls in httplib was broken (by the sendall patch
  mentioned below).

- Minor bugs in the calendar module were fixed.

- A few minor bugs in pydoc were fixed (better url recognition, proper
  quoting of some elements).

- Some distutils commands didn't list all their "boolean options"
  which made overriding them from .cfg files not work.


What's New in Python 2.2.1c1?
Release date: 18-Mar-2002
=============================

This is primarily a bugfix release.  Many bugs have been fixed since
the release of 2.2 final.  Some of the more notable are listed here.

Core and builtins

- If you try to pickle an instance of a class that has __slots__ but
  doesn't define or override __getstate__, a TypeError is now raised.
  This is done by adding a bozo __getstate__ to the class that always
  raises TypeError.  (Before, this would appear to be pickled, but the
  state of the slots would be lost.)

- (1).__nonzero__() would dump core.

- Tim has had another go at getting sensible behaviour with respect to
  floating point underflow/overflow.

- Adding an instance of subclass of int to, say, a string, could
  erroneously return "NotImplemented" instead of raising a TypeError.

- Subclassing longs could cause core dumps in certain circumstances.

- PyErr_Display will provide file and line information for all
  exceptions that have an attribute print_file_and_line, not just
  SyntaxErrors. This fixes the bug that no proper line number is given
  for bad \x escapes.

- sys.setprofile() and sys.settrace() would dump core if called with
  no arguments.

- An obscure & small memory overrun in wide unicode builds have been
  fixed.

- __doc__ can now be of arbitrary type (in particular, it can be a
  unicode string).

- complex objects are now immutable (as they should always have been).

Extension modules

- A security hole ("double free") was found in zlib-1.1.3, a popular
  third party compression library used by some Python modules.  The
  hole was quickly plugged in zlib-1.1.4, and the Windows build of
  Python 2.2.1 now ships with zlib-1.1.4.

- new.instancemethod no longer fails for new-style classes.

- The "pseudo-sequences" returned by os.stat(), os.fstat(),
  time.localtime() can now be pickled.

- Due to a cut and paste error the object exported as
  posix.statvfs_result was in fact posix.stat_result.

Library

- The copy module can be used in restricted execution mode.

- A few bugs in the email package have been fixed.

- StringIO's attitude to unicode strings has been reverted to that of
  the 2.1.x branch (note cStringIO still knows nothing about unicode).

- webbrowser: tightened up the command passed to os.system() so that
  arbitrary shell code can't be executed because a bogus URL was
  passed in.

- Recursive structures containing new-style classes can now by
  deep-copied.

- ftplib defaults to passive mode (again).

Tools

- Bugs in IDLE's autoindent when using new-style division were fixed.


What's New in Python 2.2 final?
Release date: 21-Dec-2001
===============================

Type/class unification and new-style classes

- pickle.py, cPickle: allow pickling instances of new-style classes
  with a custom metaclass.

Core and builtins

- weakref proxy object: when comparing, unwrap both arguments if both
  are proxies.

Extension modules

- binascii.b2a_base64(): fix a potential buffer overrun when encoding
  very short strings.

- cPickle: the obscure "fast" mode was suspected of causing stack
  overflows on the Mac.  Hopefully fixed this by setting the recursion
  limit much smaller.  If the limit is too low (it only affects
  performance), you can change it by defining PY_CPICKLE_FAST_LIMIT
  when compiling cPickle.c (or in pyconfig.h).

Library

- dumbdbm.py: fixed a dumb old bug (the file didn't get synched at
  close or delete time).

- rfc822.py: fixed a bug where the address '<>' was converted to None
  instead of an empty string (also fixes the email.Utils module).

- xmlrpclib.py: version 1.0.0; uses precision for doubles.

- test suite: the pickle and cPickle tests were not executing any code
  when run from the standard regresssion test.

Tools/Demos

Build

C API

New platforms

Tests

Windows

- distutils package: fixed broken Windows installers (bdist_wininst).

- tempfile.py: prevent mysterious warnings when TemporaryFileWrapper
  instances are deleted at process exit time.

- socket.py: prevent mysterious warnings when socket instances are
  deleted at process exit time.

- posixmodule.c: fix a Windows crash with stat() of a filename ending
  in backslash.

Mac

- The Carbon toolbox modules have been upgraded to Universal Headers
  3.4, and experimental CoreGraphics and CarbonEvents modules have
  been added.  All only for framework-enabled MacOSX.


What's New in Python 2.2c1?
Release date: 14-Dec-2001
===========================

Type/class unification and new-style classes

- Guido's tutorial introduction to the new type/class features has
  been extensively updated.  See

      http://www.python.org/2.2/descrintro.html

  That remains the primary documentation in this area.

- Fixed a leak: instance variables declared with __slots__ were never
  deleted!

- The "delete attribute" method of descriptor objects is called
  __delete__, not __del__.  In previous releases, it was mistakenly
  called __del__, which created an unfortunate overloading condition
  with finalizers.  (The "get attribute" and "set attribute" methods
  are still called __get__ and __set__, respectively.)

- Some subtle issues with the super built-in were fixed:

  (a) When super itself is subclassed, its __get__ method would still
      return an instance of the base class (i.e., of super).

  (b) super(C, C()).__class__ would return C rather than super.  This
      is confusing.  To fix this, I decided to change the semantics of
      super so that it only applies to code attributes, not to data
      attributes.  After all, overriding data attributes is not
      supported anyway.

  (c) The __get__ method didn't check whether the argument was an
      instance of the type used in creation of the super instance.

- Previously, hash() of an instance of a subclass of a mutable type
  (list or dictionary) would return some value, rather than raising
  TypeError.  This has been fixed.  Also, directly calling
  dict.__hash__ and list.__hash__ now raises the same TypeError
  (previously, these were the same as object.__hash__).

- New-style objects now support deleting their __dict__.  This is for
  all intents and purposes equivalent to assigning a brand new empty
  dictionary, but saves space if the object is not used further.

Core and builtins

- -Qnew now works as documented in PEP 238:  when -Qnew is passed on
  the command line, all occurrences of "/" use true division instead
  of classic division.  See the PEP for details.  Note that "all"
  means all instances in library and 3rd-party modules, as well as in
  your own code.  As the PEP says, -Qnew is intended for use only in
  educational environments with control over the libraries in use.
  Note that test_coercion.py in the standard Python test suite fails
  under -Qnew; this is expected, and won't be repaired until true
  division becomes the default (in the meantime, test_coercion is
  testing the current rules).

- complex() now only allows the first argument to be a string
  argument, and raises TypeError if either the second arg is a string
  or if the second arg is specified when the first is a string.

Extension modules

- gc.get_referents was renamed to gc.get_referrers.

Library

- Functions in the os.spawn() family now release the global interpreter
  lock around calling the platform spawn.  They should always have done
  this, but did not before 2.2c1.  Multithreaded programs calling
  an os.spawn function with P_WAIT will no longer block all Python threads
  until the spawned program completes.  It's possible that some programs
  relies on blocking, although more likely by accident than by design.

- webbrowser defaults to netscape.exe on OS/2 now.

- Tix.ResizeHandle exposes detach_widget, hide, and show.

- The charset alias windows_1252 has been added.

- types.StringTypes is a tuple containing the defined string types;
  usually this will be (str, unicode), but if Python was compiled
  without Unicode support it will be just (str,).

- The pulldom and minidom modules were synchronized to PyXML.

Tools/Demos

- A new script called Tools/scripts/google.py was added, which fires
  off a search on Google.

Build

- Note that release builds of Python should arrange to define the
  preprocessor symbol NDEBUG on the command line (or equivalent).
  In the 2.2 pre-release series we tried to define this by magic in
  Python.h instead, but it proved to cause problems for extension
  authors.  The Unix, Windows and Mac builds now all define NDEBUG in
  release builds via cmdline (or equivalent) instead.  Ports to
  other platforms should do likewise.

- It is no longer necessary to use --with-suffix when building on a
  case-insensitive file system (such as Mac OS X HFS+). In the build
  directory an extension is used, but not in the installed python.

C API

- New function PyDict_MergeFromSeq2() exposes the builtin dict
  constructor's logic for updating a dictionary from an iterable object
  producing key-value pairs.

- PyArg_ParseTupleAndKeywords() requires that the number of entries in
  the keyword list equal the number of argument specifiers.  This
  wasn't checked correctly, and PyArg_ParseTupleAndKeywords could even
  dump core in some bad cases.  This has been repaired.  As a result,
  PyArg_ParseTupleAndKeywords may raise RuntimeError in bad cases that
  previously went unchallenged.

New platforms

Tests

Windows

Mac

- In unix-Python on Mac OS X (and darwin) sys.platform is now "darwin",
  without any trailing digits.

- Changed logic for finding python home in Mac OS X framework Pythons.
  Now sys.executable points to the executable again, in stead of to
  the shared library. The latter is used only for locating the python
  home.


What's New in Python 2.2b2?
Release date: 16-Nov-2001
===========================

Type/class unification and new-style classes

- Multiple inheritance mixing new-style and classic classes in the
  list of base classes is now allowed, so this works now:

      class Classic: pass
      class Mixed(Classic, object): pass

  The MRO (method resolution order) for each base class is respected
  according to its kind, but the MRO for the derived class is computed
  using new-style MRO rules if any base clase is a new-style class.
  This needs to be documented.

- The new builtin dictionary() constructor, and dictionary type, have
  been renamed to dict.  This reflects a decade of common usage.

- dict() now accepts an iterable object producing 2-sequences.  For
  example, dict(d.items()) == d for any dictionary d.  The argument,
  and the elements of the argument, can be any iterable objects.

- New-style classes can now have a __del__ method, which is called
  when the instance is deleted (just like for classic classes).

- Assignment to object.__dict__ is now possible, for objects that are
  instances of new-style classes that have a __dict__ (unless the base
  class forbids it).

- Methods of built-in types now properly check for keyword arguments
  (formerly these were silently ignored).  The only built-in methods
  that take keyword arguments are __call__, __init__ and __new__.

- The socket function has been converted to a type; see below.

Core and builtins

- Assignment to __debug__ raises SyntaxError at compile-time.  This
  was promised when 2.1c1 was released as "What's New in Python 2.1c1"
  (see below) says.

- Clarified the error messages for unsupported operands to an operator
  (like 1 + '').

Extension modules

- mmap has a new keyword argument, "access", allowing a uniform way for
  both Windows and Unix users to create read-only, write-through and
  copy-on-write memory mappings.  This was previously possible only on
  Unix.  A new keyword argument was required to support this in a
  uniform way because the mmap() signuatures had diverged across
  platforms.  Thanks to Jay T Miller for repairing this!

- By default, the gc.garbage list now contains only those instances in
  unreachable cycles that have __del__ methods; in 2.1 it contained all
  instances in unreachable cycles.  "Instances" here has been generalized
  to include instances of both new-style and old-style classes.

- The socket module defines a new method for socket objects,
  sendall().  This is like send() but may make multiple calls to
  send() until all data has been sent.  Also, the socket function has
  been converted to a subclassable type, like list and tuple (etc.)
  before it; socket and SocketType are now the same thing.

- Various bugfixes to the curses module.  There is now a test suite
  for the curses module (you have to run it manually).

- binascii.b2a_base64 no longer places an arbitrary restriction of 57
  bytes on its input.

Library

- tkFileDialog exposes a Directory class and askdirectory
  convenience function.

- Symbolic group names in regular expressions must be unique.  For
  example, the regexp r'(?P)(?P)' is not allowed, because a
  single name can't mean both "group 1" and "group 2" simultaneously.
  Python 2.2 detects this error at regexp compilation time;
  previously, the error went undetected, and results were
  unpredictable.  Also in sre, the pattern.split(), pattern.sub(), and
  pattern.subn() methods have been rewritten in C.  Also, an
  experimental function/method finditer() has been added, which works
  like findall() but returns an iterator.

- Tix exposes more commands through the classes DirSelectBox,
  DirSelectDialog, ListNoteBook, Meter, CheckList, and the
  methods tix_addbitmapdir, tix_cget, tix_configure, tix_filedialog,
  tix_getbitmap, tix_getimage, tix_option_get, and tix_resetoptions.

- Traceback objects are now scanned by cyclic garbage collection, so
  cycles created by casual use of sys.exc_info() no longer cause
  permanent memory leaks (provided garbage collection is enabled).

- os.extsep -- a new variable needed by the RISCOS support.  It is the
  separator used by extensions, and is '.' on all platforms except
  RISCOS, where it is '/'.  There is no need to use this variable
  unless you have a masochistic desire to port your code to RISCOS.

- mimetypes.py has optional support for non-standard, but commonly
  found types.  guess_type() and guess_extension() now accept an
  optional `strict' flag, defaulting to true, which controls whether
  recognize non-standard types or not.  A few non-standard types we
  know about have been added.  Also, when run as a script, there are
  new -l and -e options.

- statcache is now deprecated.

- email.Utils.formatdate() now produces the preferred RFC 2822 style
  dates with numeric timezones (it used to produce obsolete dates
  hard coded to "GMT" timezone).  An optional `localtime' flag is
  added to produce dates in the local timezone, with daylight savings
  time properly taken into account.

- In pickle and cPickle, instead of masking errors in load() by
  transforming them into SystemError, we let the original exception
  propagate out.  Also, implement support for __safe_for_unpickling__
  in pickle, as it already was supported in cPickle.

Tools/Demos

Build

- The dbm module is built using libdb1 if available.  The bsddb module
  is built with libdb3 if available.

- Misc/Makefile.pre.in has been removed by BDFL pronouncement.

C API

- New function PySequence_Fast_GET_SIZE() returns the size of a non-
  NULL result from PySequence_Fast(), more quickly than calling
  PySequence_Size().

- New argument unpacking function PyArg_UnpackTuple() added.

- New functions PyObject_CallFunctionObjArgs() and
  PyObject_CallMethodObjArgs() have been added to make it more
  convenient and efficient to call functions and methods from C.

- PyArg_ParseTupleAndKeywords() no longer masks errors, so it's
  possible that this will propagate errors it didn't before.

- New function PyObject_CheckReadBuffer(), which returns true if its
  argument supports the single-segment readable buffer interface.

New platforms

- We've finally confirmed that this release builds on HP-UX 11.00,
  *with* threads, and passes the test suite.

- Thanks to a series of patches from Michael Muller, Python may build
  again under OS/2 Visual Age C++.

- Updated RISCOS port by Dietmar Schwertberger.

Tests

- Added a test script for the curses module.  It isn't run automatically;
  regrtest.py must be run with '-u curses' to enable it.

Windows

Mac

- PythonScript has been moved to unsupported and is slated to be
  removed completely in the next release.

- It should now be possible to build applets that work on both OS9 and
  OSX.

- The core is now linked with CoreServices not Carbon; as a side
  result, default 8bit encoding on OSX is now ASCII.

- Python should now build on OSX 10.1.1


What's New in Python 2.2b1?
Release date: 19-Oct-2001
===========================

Type/class unification and new-style classes

- New-style classes are now always dynamic (except for built-in and
  extension types).  There is no longer a performance penalty, and I
  no longer see another reason to keep this baggage around.  One relic
  remains: the __dict__ of a new-style class is a read-only proxy; you
  must set the class's attribute to modify it.  As a consequence, the
  __defined__ attribute of new-style types no longer exists, for lack
  of need: there is once again only one __dict__ (although in the
  future a __cache__ may be resurrected with a similar function, if I
  can prove that it actually speeds things up).

- C.__doc__ now works as expected for new-style classes (in 2.2a4 it
  always returned None, even when there was a class docstring).

- doctest now finds and runs docstrings attached to new-style classes,
  class methods, static methods, and properties.

Core and builtins

- A very subtle syntactical pitfall in list comprehensions was fixed.
  For example: [a+b for a in 'abc', for b in 'def'].  The comma in
  this example is a mistake.  Previously, this would silently let 'a'
  iterate over the singleton tuple ('abc',), yielding ['abcd', 'abce',
  'abcf'] rather than the intended ['ad', 'ae', 'af', 'bd', 'be',
  'bf', 'cd', 'ce', 'cf'].  Now, this is flagged as a syntax error.
  Note that [a for a in ] is a convoluted way to say
  [] anyway, so it's not like any expressiveness is lost.

- getattr(obj, name, default) now only catches AttributeError, as
  documented, rather than returning the default value for all
  exceptions (which could mask bugs in a __getattr__ hook, for
  example).

- Weak reference objects are now part of the core and offer a C API.
  A bug which could allow a core dump when binary operations involved
  proxy reference has been fixed.  weakref.ReferenceError is now a
  built-in exception.

- unicode(obj) now behaves more like str(obj), accepting arbitrary
  objects, and calling a __unicode__ method if it exists.
  unicode(obj, encoding) and unicode(obj, encoding, errors) still
  require an 8-bit string or character buffer argument.

- isinstance() now allows any object as the first argument and a
  class, a type or something with a __bases__ tuple attribute for the
  second argument.  The second argument may also be a tuple of a
  class, type, or something with __bases__, in which case isinstance()
  will return true if the first argument is an instance of any of the
  things contained in the second argument tuple.  E.g.

  isinstance(x, (A, B))

  returns true if x is an instance of A or B.

Extension modules

- thread.start_new_thread() now returns the thread ID (previously None).

- binascii has now two quopri support functions, a2b_qp and b2a_qp.

- readline now supports setting the startup_hook and the
  pre_event_hook, and adds the add_history() function.

- os and posix supports chroot(), setgroups() and unsetenv() where
  available.  The stat(), fstat(), statvfs() and fstatvfs() functions
  now return "pseudo-sequences" -- the various fields can now be
  accessed as attributes (e.g. os.stat("/").st_mtime) but for
  backwards compatibility they also behave as a fixed-length sequence.
  Some platform-specific fields (e.g. st_rdev) are only accessible as
  attributes.

- time: localtime(), gmtime() and strptime() now return a
  pseudo-sequence similar to the os.stat() return value, with
  attributes like tm_year etc.

- Decompression objects in the zlib module now accept an optional
  second parameter to decompress() that specifies the maximum amount
  of memory to use for the uncompressed data.

- optional SSL support in the socket module now exports OpenSSL
  functions RAND_add(), RAND_egd(), and RAND_status().  These calls
  are useful on platforms like Solaris where OpenSSL does not
  automatically seed its PRNG.  Also, the keyfile and certfile
  arguments to socket.ssl() are now optional.

- posixmodule (and by extension, the os module on POSIX platforms) now
  exports O_LARGEFILE, O_DIRECT, O_DIRECTORY, and O_NOFOLLOW.

Library

- doctest now excludes functions and classes not defined by the module
  being tested, thanks to Tim Hochberg.

- HotShot, a new profiler implemented using a C-based callback, has
  been added.  This substantially reduces the overhead of profiling,
  but it is still quite preliminary.  Support modules and
  documentation will be added in upcoming releases (before 2.2 final).

- profile now produces correct output in situations where an exception
  raised in Python is cleared by C code (e.g. hasattr()).  This used
  to cause wrong output, including spurious claims of recursive
  functions and attribution of time spent to the wrong function.

  The code and documentation for the derived OldProfile and HotProfile
  profiling classes was removed.  The code hasn't worked for years (if
  you tried to use them, they raised exceptions).  OldProfile
  intended to reproduce the behavior of the profiler Python used more
  than 7 years ago, and isn't interesting anymore.  HotProfile intended
  to provide a faster profiler (but producing less information), and
  that's a worthy goal we intend to meet via a different approach (but
  without losing information).

- Profile.calibrate() has a new implementation that should deliver
  a much better system-specific calibration constant.  The constant can
  now be specified in an instance constructor, or as a Profile class or
  instance variable, instead of by editing profile.py's source code.
  Calibration must still be done manually (see the docs for the profile
  module).

  Note that Profile.calibrate() must be overriden by subclasses.
  Improving the accuracy required exploiting detailed knowledge of
  profiler internals; the earlier method abstracted away the details
  and measured a simplified model instead, but consequently computed
  a constant too small by a factor of 2 on some modern machines.

- quopri's encode and decode methods take an optional header parameter,
  which indicates whether output is intended for the header 'Q'
  encoding.

- The SocketServer.ThreadingMixIn class now closes the request after
  finish_request() returns.  (Not when it errors out though.)

- The nntplib module's NNTP.body() method has grown a `file' argument
  to allow saving the message body to a file.

- The email package has added a class email.Parser.HeaderParser which
  only parses headers and does not recurse into the message's body.
  Also, the module/class MIMEAudio has been added for representing
  audio data (contributed by Anthony Baxter).

- ftplib should be able to handle files > 2GB.

- ConfigParser.getboolean() now also interprets TRUE, FALSE, YES, NO,
  ON, and OFF.

- xml.dom.minidom NodeList objects now support the length attribute
  and item() method as required by the DOM specifications.

Tools/Demos

- Demo/dns was removed.  It no longer serves any purpose; a package
  derived from it is now maintained by Anthony Baxter, see
  http://PyDNS.SourceForge.net.

- The freeze tool has been made more robust, and two new options have
  been added: -X and -E.

Build

- configure will use CXX in LINKCC if CXX is used to build main() and
  the system requires to link a C++ main using the C++ compiler.

C API

- The documentation for the tp_compare slot is updated to require that
  the return value must be -1, 0, 1; an arbitrary number <0 or >0 is
  not correct.  This is not yet enforced but will be enforced in
  Python 2.3; even later, we may use -2 to indicate errors and +2 for
  "NotImplemented".  Right now, -1 should be used for an error return.

- PyLong_AsLongLong() now accepts int (as well as long) arguments.
  Consequently, PyArg_ParseTuple's 'L' code also accepts int (as well
  as long) arguments.

- PyThread_start_new_thread() now returns a long int giving the thread
  ID, if one can be calculated; it returns -1 for error, 0 if no
  thread ID is calculated (this is an incompatible change, but only
  the thread module used this API).  This code has only really been
  tested on Linux and Windows; other platforms please beware (and
  report any bugs or strange behavior).

- PyUnicode_FromEncodedObject() no longer accepts Unicode objects as
  input.

New platforms

Tests

Windows

- Installer:  If you install IDLE, and don't disable file-extension
  registration, a new "Edit with IDLE" context (right-click) menu entry
  is created for .py and .pyw files.

- The signal module now supports SIGBREAK on Windows, thanks to Steven
  Scott.  Note that SIGBREAK is unique to Windows.  The default SIGBREAK
  action remains to call Win32 ExitProcess().  This can be changed via
  signal.signal().  For example:

  # Make Ctrl+Break raise KeyboardInterrupt, like Python's default Ctrl+C
  # (SIGINT) behavior.
  import signal
  signal.signal(signal.SIGBREAK,
                signal.default_int_handler)

  try:
      while 1:
          pass
  except KeyboardInterrupt:
      # We get here on Ctrl+C or Ctrl+Break now; if we had not changed
      # SIGBREAK, only on Ctrl+C (and Ctrl+Break would terminate the
      # program without the possibility for any Python-level cleanup).
      print "Clean exit"


What's New in Python 2.2a4?
Release date: 28-Sep-2001
===========================

Type/class unification and new-style classes

- pydoc and inspect are now aware of new-style classes;
  e.g. help(list) at the interactive prompt now shows proper
  documentation for all operations on list objects.

- Applications using Jim Fulton's ExtensionClass module can now safely
  be used with Python 2.2.  In particular, Zope 2.4.1 now works with
  Python 2.2 (as well as with Python 2.1.1).  The Demo/metaclass
  examples also work again.  It is hoped that Gtk and Boost also work
  with 2.2a4 and beyond.  (If you can confirm this, please write
  webmaster@python.org; if there are still problems, please open a bug
  report on SourceForge.)

- property() now takes 4 keyword arguments:  fget, fset, fdel and doc.
  These map to readonly attributes 'fget', 'fset', 'fdel', and '__doc__'
  in the constructed property object.  fget, fset and fdel weren't
  discoverable from Python in 2.2a3.  __doc__ is new, and allows to
  associate a docstring with a property.

- Comparison overloading is now more completely implemented.  For
  example, a str subclass instance can properly be compared to a str
  instance, and it can properly overload comparison.  Ditto for most
  other built-in object types.

- The repr() of new-style classes has changed; instead of  a new-style class is now rendered as ,
  *except* for built-in types, which are still rendered as  (to avoid upsetting existing code that might parse or
  otherwise rely on repr() of certain type objects).

- The repr() of new-style objects is now always ;
  previously, it was sometimes .

- For new-style classes, what was previously called __getattr__ is now
  called __getattribute__.  This method, if defined, is called for
  *every* attribute access.  A new __getattr__ hook more similar to the
  one in classic classes is defined which is called only if regular
  attribute access raises AttributeError; to catch *all* attribute
  access, you can use __getattribute__ (for new-style classes).  If
  both are defined, __getattribute__ is called first, and if it raises
  AttributeError, __getattr__ is called.

- The __class__ attribute of new-style objects can be assigned to.
  The new class must have the same C-level object layout as the old
  class.

- The builtin file type can be subclassed now.  In the usual pattern,
  "file" is the name of the builtin type, and file() is a new builtin
  constructor, with the same signature as the builtin open() function.
  file() is now the preferred way to open a file.

- Previously, __new__ would only see sequential arguments passed to
  the type in a constructor call; __init__ would see both sequential
  and keyword arguments.  This made no sense whatsoever any more, so
  now both __new__ and __init__ see all arguments.

- Previously, hash() applied to an instance of a subclass of str or
  unicode always returned 0.  This has been repaired.

- Previously, an operation on an instance of a subclass of an
  immutable type (int, long, float, complex, tuple, str, unicode),
  where the subtype didn't override the operation (and so the
  operation was handled by the builtin type), could return that
  instance instead a value of the base type.  For example, if s was of
  a str sublass type, s[:] returned s as-is.  Now it returns a str
  with the same value as s.

- Provisional support for pickling new-style objects has been added.

Core

- file.writelines() now accepts any iterable object producing strings.

- PyUnicode_FromEncodedObject() now works very much like
  PyObject_Str(obj) in that it tries to use __str__/tp_str
  on the object if the object is not a string or buffer. This
  makes unicode() behave like str() when applied to non-string/buffer
  objects.

- PyFile_WriteObject now passes Unicode objects to the file's write
  method. As a result, all file-like objects which may be the target
  of a print statement must support Unicode objects, i.e. they must
  at least convert them into ASCII strings.

- Thread scheduling on Solaris should be improved; it is no longer
  necessary to insert a small sleep at the start of a thread in order
  to let other runnable threads be scheduled.

Library

- StringIO.StringIO instances and cStringIO.StringIO instances support
  read character buffer compatible objects for their .write() methods.
  These objects are converted to strings and then handled as such
  by the instances.

- The "email" package has been added.  This is basically a port of the
  mimelib package  with API changes
  and some implementations updated to use iterators and generators.

- difflib.ndiff() and difflib.Differ.compare() are generators now.  This
  restores the ability of Tools/scripts/ndiff.py to start producing output
  before the entire comparison is complete.

- StringIO.StringIO instances and cStringIO.StringIO instances support
  iteration just like file objects (i.e. their .readline() method is
  called for each iteration until it returns an empty string).

- The codecs module has grown four new helper APIs to access
  builtin codecs: getencoder(), getdecoder(), getreader(),
  getwriter().

- SimpleXMLRPCServer: a new module (based upon SimpleHTMLServer)
  simplifies writing XML RPC servers.

- os.path.realpath(): a new function that returns the absolute pathname
  after interpretation of symbolic links.  On non-Unix systems, this
  is an alias for os.path.abspath().

- operator.indexOf() (PySequence_Index() in the C API) now works with any
  iterable object.

- smtplib now supports various authentication and security features of
  the SMTP protocol through the new login() and starttls() methods.

- hmac: a new module implementing keyed hashing for message
  authentication.

- mimetypes now recognizes more extensions and file types.  At the
  same time, some mappings not sanctioned by IANA were removed.

- The "compiler" package has been brought up to date to the state of
  Python 2.2 bytecode generation.  It has also been promoted from a
  Tool to a standard library package.  (Tools/compiler still exists as
  a sample driver.)

Tools

Build

- Large file support (LFS) is now automatic when the platform supports
  it; no more manual configuration tweaks are needed.  On Linux, at
  least, it's possible to have a system whose C library supports large
  files but whose kernel doesn't; in this case, large file support is
  still enabled but doesn't do you any good unless you upgrade your
  kernel or share your Python executable with another system whose
  kernel has large file support.

- The configure script now supplies plausible defaults in a
  cross-compilation environment.  This doesn't mean that the supplied
  values are always correct, or that cross-compilation now works
  flawlessly -- but it's a first step (and it shuts up most of
  autoconf's warnings about AC_TRY_RUN).

- The Unix build is now a bit less chatty, courtesy of the parser
  generator.  The build is completely silent (except for errors) when
  using "make -s", thanks to a -q option to setup.py.

C API

- The "structmember" API now supports some new flag bits to deny read
  and/or write access to attributes in restricted execution mode.

New platforms

- Compaq's iPAQ handheld, running the "familiar" Linux distribution
  (http://familiar.handhelds.org).

Tests

- The "classic" standard tests, which work by comparing stdout to
  an expected-output file under Lib/test/output/, no longer stop at
  the first mismatch.  Instead the test is run to completion, and a
  variant of ndiff-style comparison is used to report all differences.
  This is much easier to understand than the previous style of reporting.

- The unittest-based standard tests now use regrtest's test_main()
  convention, instead of running as a side-effect of merely being
  imported.  This allows these tests to be run in more natural and
  flexible ways as unittests, outside the regrtest framework.

- regrtest.py is much better integrated with unittest and doctest now,
  especially in regard to reporting errors.

Windows

- Large file support now also works for files > 4GB, on filesystems
  that support it (NTFS under Windows 2000).  See "What's New in
  Python 2.2a3" for more detail.


What's New in Python 2.2a3?
Release Date: 07-Sep-2001
===========================

Core

- Conversion of long to float now raises OverflowError if the long is too
  big to represent as a C double.

- The 3-argument builtin pow() no longer allows a third non-None argument
  if either of the first two arguments is a float, or if both are of
  integer types and the second argument is negative (in which latter case
  the arguments are converted to float, so this is really the same
  restriction).

- The builtin dir() now returns more information, and sometimes much
  more, generally naming all attributes of an object, and all attributes
  reachable from the object via its class, and from its class's base
  classes, and so on from them too.  Example:  in 2.2a2, dir([]) returned
  an empty list.  In 2.2a3,

  >>> dir([])
  ['__add__', '__class__', '__contains__', '__delattr__', '__delitem__',
   '__eq__', '__ge__', '__getattr__', '__getitem__', '__getslice__',
   '__gt__', '__hash__', '__iadd__', '__imul__', '__init__', '__le__',
   '__len__', '__lt__', '__mul__', '__ne__', '__new__', '__repr__',
   '__rmul__', '__setattr__', '__setitem__', '__setslice__', '__str__',
   'append', 'count', 'extend', 'index', 'insert', 'pop', 'remove',
   'reverse', 'sort']

  dir(module) continues to return only the module's attributes, though.

- Overflowing operations on plain ints now return a long int rather
  than raising OverflowError.  This is a partial implementation of PEP
  237.  You can use -Wdefault::OverflowWarning to enable a warning for
  this situation, and -Werror::OverflowWarning to revert to the old
  OverflowError exception.

- A new command line option, -Q, is added to control run-time
  warnings for the use of classic division.  (See PEP 238.)  Possible
  values are -Qold, -Qwarn, -Qwarnall, and -Qnew.  The default is
  -Qold, meaning the / operator has its classic meaning and no
  warnings are issued.  Using -Qwarn issues a run-time warning about
  all uses of classic division for int and long arguments; -Qwarnall
  also warns about classic division for float and complex arguments
  (for use with fixdiv.py).
  [Note:  the remainder of this paragraph (preserved below) became
   obsolete in 2.2c1 -- -Qnew has global effect in 2.2]
  
  Using -Qnew is questionable; it turns on new division by default, but
  only in the __main__ module.  You can usefully combine -Qwarn or
  -Qwarnall and -Qnew: this gives the __main__ module new division, and
  warns about classic division everywhere else.
  

- Many built-in types can now be subclassed.  This applies to int,
  long, float, str, unicode, and tuple.  (The types complex, list and
  dictionary can also be subclassed; this was introduced earlier.)
  Note that restrictions apply when subclassing immutable built-in
  types: you can only affect the value of the instance by overloading
  __new__.  You can add mutable attributes, and the subclass instances
  will have a __dict__ attribute, but you cannot change the "value"
  (as implemented by the base class) of an immutable subclass instance
  once it is created.

- The dictionary constructor now takes an optional argument, a
  mapping-like object, and initializes the dictionary from its
  (key, value) pairs.

- A new built-in type, super, has been added.  This facilitates making
  "cooperative super calls" in a multiple inheritance setting.  For an
  explanation, see http://www.python.org/2.2/descrintro.html#cooperation

- A new built-in type, property, has been added.  This enables the
  creation of "properties".  These are attributes implemented by
  getter and setter functions (or only one of these for read-only or
  write-only attributes), without the need to override __getattr__.
  See http://www.python.org/2.2/descrintro.html#property

- The syntax of floating-point and imaginary literals has been
  liberalized, to allow leading zeroes.  Examples of literals now
  legal that were SyntaxErrors before:

      00.0    0e3   0100j   07.5   00000000000000000008.

- An old tokenizer bug allowed floating point literals with an incomplete
  exponent, such as 1e and 3.1e-.  Such literals now raise SyntaxError.

Library

- telnetlib includes symbolic names for the options, and support for
  setting an option negotiation callback.

- The new C standard no longer requires that math libraries set errno to
  ERANGE on overflow.  For platform libraries that exploit this new
  freedom, Python's overflow-checking was wholly broken.  A new overflow-
  checking scheme attempts to repair that, but may not be reliable on all
  platforms (C doesn't seem to provide anything both useful and portable
  in this area anymore).

- Asynchronous timeout actions are available through the new class
  threading.Timer.

- math.log and math.log10 now return sensible results for even huge
  long arguments.  For example, math.log10(10 ** 10000) ~= 10000.0.

- A new function, imp.lock_held(), returns 1 when the import lock is
  currently held.  See the docs for the imp module.

- pickle, cPickle and marshal on 32-bit platforms can now correctly read
  dumps containing ints written on platforms where Python ints are 8 bytes.
  When read on a box where Python ints are 4 bytes, such values are
  converted to Python longs.

- In restricted execution mode (using the rexec module), unmarshalling
  code objects is no longer allowed.  This plugs a security hole.

- unittest.TestResult instances no longer store references to tracebacks
  generated by test failures. This prevents unexpected dangling references
  to objects that should be garbage collected between tests.

Tools

- Tools/scripts/fixdiv.py has been added which can be used to fix
  division operators as per PEP 238.

Build

- If you are an adventurous person using Mac OS X you may want to look at
  Mac/OSX. There is a Makefile there that will build Python as a real Mac
  application, which can be used for experimenting with Carbon or Cocoa.
  Discussion of this on pythonmac-sig, please.

C API

- New function PyObject_Dir(obj), like Python __builtin__.dir(obj).

- Note that PyLong_AsDouble can fail!  This has always been true, but no
  callers checked for it.  It's more likely to fail now, because overflow
  errors are properly detected now.  The proper way to check:

  double x = PyLong_AsDouble(some_long_object);
  if (x == -1.0 && PyErr_Occurred()) {
          /* The conversion failed. */
  }

- The GC API has been changed.  Extensions that use the old API will still
  compile but will not participate in GC.  To upgrade an extension
  module:

    - rename Py_TPFLAGS_GC to PyTPFLAGS_HAVE_GC

    - use PyObject_GC_New or PyObject_GC_NewVar to allocate objects and
      PyObject_GC_Del to deallocate them

    - rename PyObject_GC_Init to PyObject_GC_Track and PyObject_GC_Fini
      to PyObject_GC_UnTrack

    - remove PyGC_HEAD_SIZE from object size calculations

    - remove calls to PyObject_AS_GC and PyObject_FROM_GC

- Two new functions: PyString_FromFormat() and PyString_FromFormatV().
  These can be used safely to construct string objects from a
  sprintf-style format string (similar to the format string supported
  by PyErr_Format()).

New platforms

- Stephen Hansen contributed patches sufficient to get a clean compile
  under Borland C (Windows), but he reports problems running it and ran
  out of time to complete the port.  Volunteers?  Expect a MemoryError
  when importing the types module; this is probably shallow, and
  causing later failures too.

Tests

Windows

- Large file support is now enabled on Win32 platforms as well as on
  Win64.  This means that, for example, you can use f.tell() and f.seek()
  to manipulate files larger than 2 gigabytes (provided you have enough
  disk space, and are using a Windows filesystem that supports large
  partitions).  Windows filesystem limits:  FAT has a 2GB (gigabyte)
  filesize limit, and large file support makes no difference there.
  FAT32's limit is 4GB, and files >= 2GB are easier to use from Python now.
  NTFS has no practical limit on file size, and files of any size can be
  used from Python now.

- The w9xpopen hack is now used on Windows NT and 2000 too when COMPSPEC
  points to command.com (patch from Brian Quinlan).


What's New in Python 2.2a2?
Release Date: 22-Aug-2001
===========================

Build

- Tim Peters developed a brand new Windows installer using Wise 8.1,
  generously donated to us by Wise Solutions.

- configure supports a new option --enable-unicode, with the values
  ucs2 and ucs4 (new in 2.2a1). With --disable-unicode, the Unicode
  type and supporting code is completely removed from the interpreter.

- A new configure option --enable-framework builds a Mac OS X framework,
  which "make frameworkinstall" will install. This provides a starting
  point for more mac-like functionality, join pythonmac-sig@python.org
  if you are interested in helping.

- The NeXT platform is no longer supported.

- The `new' module is now statically linked.

Tools

- The new Tools/scripts/cleanfuture.py can be used to automatically
  edit out obsolete future statements from Python source code.  See
  the module docstring for details.

Tests

- regrtest.py now knows which tests are expected to be skipped on some
  platforms, allowing to give clearer test result output.  regrtest
  also has optional --use/-u switch to run normally disabled tests
  which require network access or consume significant disk resources.

- Several new tests in the standard test suite, with special thanks to
  Nick Mathewson.

Core

- The floor division operator // has been added as outlined in PEP
  238.  The / operator still provides classic division (and will until
  Python 3.0) unless "from __future__ import division" is included, in
  which case the / operator will provide true division.  The operator
  module provides truediv() and floordiv() functions.  Augmented
  assignment variants are included, as are the equivalent overloadable
  methods and C API methods.  See the PEP for a full discussion:
  

- Future statements are now effective in simulated interactive shells
  (like IDLE).  This should "just work" by magic, but read Michael
  Hudson's "Future statements in simulated shells" PEP 264 for full
  details:  .

- The type/class unification (PEP 252-253) was integrated into the
  trunk and is not so tentative any more (the exact specification of
  some features is still tentative).  A lot of work has done on fixing
  bugs and adding robustness and features (performance still has to
  come a long way).

- Warnings about a mismatch in the Python API during extension import
  now use the Python warning framework (which makes it possible to
  write filters for these warnings).

- A function's __dict__ (aka func_dict) will now always be a
  dictionary.  It used to be possible to delete it or set it to None,
  but now both actions raise TypeErrors.  It is still legal to set it
  to a dictionary object.  Getting func.__dict__ before any attributes
  have been assigned now returns an empty dictionary instead of None.

- A new command line option, -E, was added which disables the use of
  all environment variables, or at least those that are specifically
  significant to Python.  Usually those have a name starting with
  "PYTHON".  This was used to fix a problem where the tests fail if
  the user happens to have PYTHONHOME or PYTHONPATH pointing to an
  older distribution.

Library

- New class Differ and new functions ndiff() and restore() in difflib.py.
  These package the algorithms used by the popular Tools/scripts/ndiff.py,
  for programmatic reuse.

- New function xml.sax.saxutils.quoteattr():  Quote an XML attribute
  value using the minimal quoting required for the value; more
  reliable than using xml.sax.saxutils.escape() for attribute values.

- Readline completion support for cmd.Cmd was added.

- Calling os.tempnam() or os.tmpnam() generate RuntimeWarnings.

- Added function threading.BoundedSemaphore()

- Added Ka-Ping Yee's cgitb.py module.

- The `new' module now exposes the CO_xxx flags.

- The gc module offers the get_referents function.

New platforms

C API

- Two new APIs PyOS_snprintf() and PyOS_vsnprintf() were added
  which provide a cross-platform implementations for the
  relatively new snprintf()/vsnprintf() C lib APIs. In contrast to
  the standard sprintf() and vsprintf() C lib APIs, these versions
  apply bounds checking on the used buffer which enhances protection
  against buffer overruns.

- Unicode APIs now use name mangling to assure that mixing interpreters
  and extensions using different Unicode widths is rendered next to
  impossible. Trying to import an incompatible Unicode-aware extension
  will result in an ImportError.  Unicode extensions writers must make
  sure to check the Unicode width compatibility in their extensions by
  using at least one of the mangled Unicode APIs in the extension.

- Two new flags METH_NOARGS and METH_O are available in method definition
  tables to simplify implementation of methods with no arguments and a
  single untyped argument. Calling such methods is more efficient than
  calling corresponding METH_VARARGS methods. METH_OLDARGS is now
  deprecated.

Windows

- "import module" now compiles module.pyw if it exists and nothing else
  relevant is found.


What's New in Python 2.2a1?
Release date: 18-Jul-2001
===========================

Core

- TENTATIVELY, a large amount of code implementing much of what's
  described in PEP 252 (Making Types Look More Like Classes) and PEP
  253 (Subtyping Built-in Types) was added.  This will be released
  with Python 2.2a1.  Documentation will be provided separately
  through http://www.python.org/2.2/.  The purpose of releasing this
  with Python 2.2a1 is to test backwards compatibility.  It is
  possible, though not likely, that a decision is made not to release
  this code as part of 2.2 final, if any serious backwards
  incompapatibilities are found during alpha testing that cannot be
  repaired.

- Generators were added; this is a new way to create an iterator (see
  below) using what looks like a simple function containing one or
  more 'yield' statements.  See PEP 255.  Since this adds a new
  keyword to the language, this feature must be enabled by including a
  future statement: "from __future__ import generators" (see PEP 236).
  Generators will become a standard feature in a future release
  (probably 2.3).  Without this future statement, 'yield' remains an
  ordinary identifier, but a warning is issued each time it is used.
  (These warnings currently don't conform to the warnings framework of
  PEP 230; we intend to fix this in 2.2a2.)

- The UTF-16 codec was modified to be more RFC compliant. It will now
  only remove BOM characters at the start of the string and then
  only if running in native mode (UTF-16-LE and -BE won't remove a
  leading BMO character).

- Strings now have a new method .decode() to complement the already
  existing .encode() method. These two methods provide direct access
  to the corresponding decoders and encoders of the registered codecs.

  To enhance the usability of the .encode() method, the special
  casing of Unicode object return values was dropped (Unicode objects
  were auto-magically converted to string using the default encoding).

  Both methods will now return whatever the codec in charge of the
  requested encoding returns as object, e.g. Unicode codecs will
  return Unicode objects when decoding is requested ("äöü".decode("latin-1")
  will return u"äöü"). This enables codec writer to create codecs
  for various simple to use conversions.

  New codecs were added to demonstrate these new features (the .encode()
  and .decode() columns indicate the type of the returned objects):

  Name     | .encode() | .decode() | Description
  ----------------------------------------------------------------------
  uu       | string    | string    | UU codec (e.g. for email)
  base64   | string    | string    | base64 codec
  quopri   | string    | string    | quoted-printable codec
  zlib     | string    | string    | zlib compression
  hex      | string    | string    | 2-byte hex codec
  rot-13   | string    | Unicode   | ROT-13 Unicode charmap codec

- Some operating systems now support the concept of a default Unicode
  encoding for file system operations.  Notably, Windows supports 'mbcs'
  as the default.  The Macintosh will also adopt this concept in the medium
  term, although the default encoding for that platform will be other than
  'mbcs'.

  On operating system that support non-ASCII filenames, it is common for
  functions that return filenames (such as os.listdir()) to return Python
  string objects pre-encoded using the default file system encoding for
  the platform.  As this encoding is likely to be different from Python's
  default encoding, converting this name to a Unicode object before passing
  it back to the Operating System would result in a Unicode error, as Python
  would attempt to use its default encoding (generally ASCII) rather than
  the default encoding for the file system.

  In general, this change simply removes surprises when working with
  Unicode and the file system, making these operations work as you expect,
  increasing the transparency of Unicode objects in this context.
  See [????] for more details, including examples.

- Float (and complex) literals in source code were evaluated to full
  precision only when running from a .py file; the same code loaded from a
  .pyc (or .pyo) file could suffer numeric differences starting at about the
  12th significant decimal digit.  For example, on a machine with IEEE-754
  floating arithmetic,

      x = 9007199254740992.0
      print long(x)

  printed 9007199254740992 if run directly from .py, but 9007199254740000
  if from a compiled (.pyc or .pyo) file.  This was due to marshal using
  str(float) instead of repr(float) when building code objects.  marshal
  now uses repr(float) instead, which should reproduce floats to full
  machine precision (assuming the platform C float<->string I/O conversion
  functions are of good quality).

  This may cause floating-point results to change in some cases, and
  usually for the better, but may also cause numerically unstable
  algorithms to break.

- The implementation of dicts suffers fewer collisions, which has speed
  benefits.  However, the order in which dict entries appear in dict.keys(),
  dict.values() and dict.items() may differ from previous releases for a
  given dict.  Nothing is defined about this order, so no program should
  rely on it.  Nevertheless, it's easy to write test cases that rely on the
  order by accident, typically because of printing the str() or repr() of a
  dict to an "expected results" file.  See Lib/test/test_support.py's new
  sortdict(dict) function for a simple way to display a dict in sorted
  order.

- Many other small changes to dicts were made, resulting in faster
  operation along the most common code paths.

- Dictionary objects now support the "in" operator: "x in dict" means
  the same as dict.has_key(x).

- The update() method of dictionaries now accepts generic mapping
  objects.  Specifically the argument object must support the .keys()
  and __getitem__() methods.  This allows you to say, for example,
  {}.update(UserDict())

- Iterators were added; this is a generalized way of providing values
  to a for loop.  See PEP 234.  There's a new built-in function iter()
  to return an iterator.  There's a new protocol to get the next value
  from an iterator using the next() method (in Python) or the
  tp_iternext slot (in C).  There's a new protocol to get iterators
  using the __iter__() method (in Python) or the tp_iter slot (in C).
  Iterating (i.e. a for loop) over a dictionary generates its keys.
  Iterating over a file generates its lines.

- The following functions were generalized to work nicely with iterator
  arguments:
    map(), filter(), reduce(), zip()
    list(), tuple() (PySequence_Tuple() and PySequence_Fast() in C API)
    max(), min()
    join() method of strings
    extend() method of lists
    'x in y' and 'x not in y' (PySequence_Contains() in C API)
    operator.countOf() (PySequence_Count() in C API)
    right-hand side of assignment statements with multiple targets, such as
        x, y, z = some_iterable_object_returning_exactly_3_values

- Accessing module attributes is significantly faster (for example,
  random.random or os.path or yourPythonModule.yourAttribute).

- Comparing dictionary objects via == and != is faster, and now works even
  if the keys and values don't support comparisons other than ==.

- Comparing dictionaries in ways other than == and != is slower:  there were
  insecurities in the dict comparison implementation that could cause Python
  to crash if the element comparison routines for the dict keys and/or
  values mutated the dicts.  Making the code bulletproof slowed it down.

- Collisions in dicts are resolved via a new approach, which can help
  dramatically in bad cases.  For example, looking up every key in a dict
  d with d.keys() == [i << 16 for i in range(20000)] is approximately 500x
  faster now.  Thanks to Christian Tismer for pointing out the cause and
  the nature of an effective cure (last December! better late than never).

- repr() is much faster for large containers (dict, list, tuple).


Library

- The constants ascii_letters, ascii_lowercase. and ascii_uppercase
  were added to the string module.  These a locale-indenpendent
  constants, unlike letters, lowercase, and uppercase.  These are now
  use in appropriate locations in the standard library.

- The flags used in dlopen calls can now be configured using
  sys.setdlopenflags and queried using sys.getdlopenflags.

- Fredrik Lundh's xmlrpclib is now a standard library module.  This
  provides full client-side XML-RPC support.  In addition,
  Demo/xmlrpc/ contains two server frameworks (one SocketServer-based,
  one asyncore-based).  Thanks to Eric Raymond for the documentation.

- The xrange() object is simplified: it no longer supports slicing,
  repetition, comparisons, efficient 'in' checking, the tolist()
  method, or the start, stop and step attributes.  See PEP 260.

- A new function fnmatch.filter to filter lists of file names was added.

- calendar.py uses month and day names based on the current locale.

- strop is now *really* obsolete (this was announced before with 1.6),
  and issues DeprecationWarning when used (except for the four items
  that are still imported into string.py).

- Cookie.py now sorts key+value pairs by key in output strings.

- pprint.isrecursive(object) didn't correctly identify recursive objects.
  Now it does.

- pprint functions now much faster for large containers (tuple, list, dict).

- New 'q' and 'Q' format codes in the struct module, corresponding to C
  types "long long" and "unsigned long long" (on Windows, __int64).  In
  native mode, these can be used only when the platform C compiler supports
  these types (when HAVE_LONG_LONG is #define'd by the Python config
  process), and then they inherit the sizes and alignments of the C types.
  In standard mode, 'q' and 'Q' are supported on all platforms, and are
  8-byte integral types.

- The site module installs a new built-in function 'help' that invokes
  pydoc.help.  It must be invoked as 'help()'; when invoked as 'help',
  it displays a message reminding the user to use 'help()' or
  'help(object)'.

Tests

- New test_mutants.py runs dict comparisons where the key and value
  comparison operators mutute the dicts randomly during comparison.  This
  rapidly causes Python to crash under earlier releases (not for the faint
  of heart:  it can also cause Win9x to freeze or reboot!).

- New test_pprint.py verfies that pprint.isrecursive() and
  pprint.isreadable() return sensible results.  Also verifies that simple
  cases produce correct output.

C API

- Removed the unused last_is_sticky argument from the internal
  _PyTuple_Resize().  If this affects you, you were cheating.


======================================================================


What's New in Python 2.1 (final)?
=================================

We only changed a few things since the last release candidate, all in
Python library code:

- A bug in the locale module was fixed that affected locales which
  define no grouping for numeric formatting.

- A few bugs in the weakref module's implementations of weak
  dictionaries (WeakValueDictionary and WeakKeyDictionary) were fixed,
  and the test suite was updated to check for these bugs.

- An old bug in the os.path.walk() function (introduced in Python
  2.0!) was fixed: a non-existent file would cause an exception
  instead of being ignored.

- Fixed a few bugs in the new symtable module found by Neil Norwitz's
  PyChecker.


What's New in Python 2.1c2?
===========================

A flurry of small changes, and one showstopper fixed in the nick of
time made it necessary to release another release candidate.  The list
here is the *complete* list of patches (except version updates):

Core

- Tim discovered a nasty bug in the dictionary code, caused by
  PyDict_Next() calling dict_resize(), and the GC code's use of
  PyDict_Next() violating an assumption in dict_items().  This was
  fixed with considerable amounts of band-aid, but the net effect is a
  saner and more robust implementation.

- Made a bunch of symbols static that were accidentally global.

Build and Ports

- The setup.py script didn't check for a new enough version of zlib
  (1.1.3 is needed).  Now it does.

- Changed "make clean" target to also remove shared libraries.

- Added a more general warning about the SGI Irix optimizer to README.

Library

- Fix a bug in urllib.basejoin("http://host", "../file.html") which
  omitted the slash between host and file.html.

- The mailbox module's _Mailbox class contained a completely broken
  and undocumented seek() method.  Ripped it out.

- Fixed a bunch of typos in various library modules (urllib2, smtpd,
  sgmllib, netrc, chunk) found by Neil Norwitz's PyChecker.

- Fixed a few last-minute bugs in unittest.

Extensions

- Reverted the patch to the OpenSSL code in socketmodule.c to support
  RAND_status() and the EGD, and the subsequent patch that tried to
  fix it for pre-0.9.5 versions; the problem with the patch is that on
  some systems it issues a warning whenever socket is imported, and
  that's unacceptable.

Tests

- Fixed the pickle tests to work with "import test.test_pickle".

- Tweaked test_locale.py to actually run the test Windows.

- In distutils/archive_util.py, call zipfile.ZipFile() with mode "w",
  not "wb" (which is not a valid mode at all).

- Fix pstats browser crashes.  Import readline if it exists to make
  the user interface nicer.

- Add "import thread" to the top of test modules that import the
  threading module (test_asynchat and test_threadedtempfile).  This
  prevents test failures caused by a broken threading module resulting
  from a previously caught failed import.

- Changed test_asynchat.py to set the SO_REUSEADDR option; this was
  needed on some platforms (e.g. Solaris 8) when the tests are run
  twice in succession.

- Skip rather than fail test_sunaudiodev if no audio device is found.


What's New in Python 2.1c1?
===========================

This list was significantly updated when 2.1c2 was released; the 2.1c1
release didn't mention most changes that were actually part of 2.1c1:

Legal

- Copyright was assigned to the Python Software Foundation (PSF) and a
  PSF license (very similar to the CNRI license) was added.

- The CNRI copyright notice was updated to include 2001.

Core

- After a public outcry, assignment to __debug__ is no longer illegal;
  instead, a warning is issued.  It will become illegal in 2.2.

- Fixed a core dump with "%#x" % 0, and changed the semantics so that
  "%#x" now always prepends "0x", even if the value is zero.

- Fixed some nits in the bytecode compiler.

- Fixed core dumps when calling certain kinds of non-functions.

- Fixed various core dumps caused by reference count bugs.

Build and Ports

- Use INSTALL_SCRIPT to install script files.

- New port: SCO Unixware 7, by Billy G. Allie.

- Updated RISCOS port.

- Updated BeOS port and notes.

- Various other porting problems resolved.

Library

- The TERMIOS and SOCKET modules are now truly obsolete and
  unnecessary.  Their symbols are incorporated in the termios and
  socket modules.

- Fixed some 64-bit bugs in pickle, cPickle, and struct, and added
  better tests for pickling.

- threading: make Condition.wait() robust against KeyboardInterrupt.

- zipfile: add support to zipfile to support opening an archive
  represented by an open file rather than a file name.  Fix bug where
  the archive was not properly closed.  Fixed a bug in this bugfix
  where flush() was called for a read-only file.

- imputil: added an uninstall() method to the ImportManager.

- Canvas: fixed bugs in lower() and tkraise() methods.

- SocketServer: API change (added overridable close_request() method)
  so that the TCP server can explicitly close the request.

- pstats: Eric Raymond added a simple interactive statistics browser,
  invoked when the module is run as a script.

- locale: fixed a problem in format().

- webbrowser: made it work when the BROWSER environment variable has a
  value like "/usr/bin/netscape".  Made it auto-detect Konqueror for
  KDE 2.  Fixed some other nits.

- unittest: changes to allow using a different exception than
  AssertionError, and added a few more function aliases.  Some other
  small changes.

- urllib, urllib2: fixed redirect problems and a coupleof other nits.

- asynchat: fixed a critical bug in asynchat that slipped through the
  2.1b2 release.  Fixed another rare bug.

- Fix some unqualified except: clauses (always a bad code example).

XML

- pyexpat: new API get_version_string().

- Fixed some minidom bugs.

Extensions

- Fixed a core dump in _weakref.  Removed the weakref.mapping()
  function (it adds nothing to the API).

- Rationalized the use of header files in the readline module, to make
  it compile (albeit with some warnings) with the very recent readline
  4.2, without breaking for earlier versions.

- Hopefully fixed a buffering problem in linuxaudiodev.

- Attempted a fix to make the OpenSSL support in the socket module
  work again with pre-0.9.5 versions of OpenSSL.

Tests

- Added a test case for asynchat and asyncore.

- Removed coupling between tests where one test failing could break
  another.

Tools

- Ping added an interactive help browser to pydoc, fixed some nits
  in the rest of the pydoc code, and added some features to his
  inspect module.

- An updated python-mode.el version 4.1 which integrates Ken
  Manheimer's pdbtrack.el.  This makes debugging Python code via pdb
  much nicer in XEmacs and Emacs.  When stepping through your program
  with pdb, in either the shell window or the *Python* window, the
  source file and line will be tracked by an arrow.  Very cool!

- IDLE: syntax warnings in interactive mode are changed into errors.

- Some improvements to Tools/webchecker (ignore some more URL types,
  follow some more links).

- Brought the Tools/compiler package up to date.


What's New in Python 2.1 beta 2?
================================

(Unlisted are many fixed bugs, more documentation, etc.)

Core language, builtins, and interpreter

- The nested scopes work (enabled by "from __future__ import
  nested_scopes") is completed; in particular, the future now extends
  into code executed through exec, eval() and execfile(), and into the
  interactive interpreter.

- When calling a base class method (e.g. BaseClass.__init__(self)),
  this is now allowed even if self is not strictly spoken a class
  instance (e.g. when using metaclasses or the Don Beaudry hook).

- Slice objects are now comparable but not hashable; this prevents
  dict[:] from being accepted but meaningless.

- Complex division is now calculated using less braindead algorithms.
  This doesn't change semantics except it's more likely to give useful
  results in extreme cases.  Complex repr() now uses full precision
  like float repr().

- sgmllib.py now calls handle_decl() for simple  declarations.

- It is illegal to assign to the name __debug__, which is set when the
  interpreter starts.  It is effectively a compile-time constant.

- A warning will be issued if a global statement for a variable
  follows a use or assignment of that variable.

Standard library

- unittest.py, a unit testing framework by Steve Purcell (PyUNIT,
  inspired by JUnit), is now part of the standard library.  You now
  have a choice of two testing frameworks: unittest requires you to
  write testcases as separate code, doctest gathers them from
  docstrings.  Both approaches have their advantages and
  disadvantages.

- A new module Tix was added, which wraps the Tix extension library
  for Tk.  With that module, it is not necessary to statically link
  Tix with _tkinter, since Tix will be loaded with Tcl's "package
  require" command.  See Demo/tix/.

- tzparse.py is now obsolete.

- In gzip.py, the seek() and tell() methods are removed -- they were
  non-functional anyway, and it's better if callers can test for their
  existence with hasattr().

Python/C API

- PyDict_Next(): it is now safe to call PyDict_SetItem() with a key
  that's already in the dictionary during a PyDict_Next() iteration.
  This used to fail occasionally when a dictionary resize operation
  could be triggered that would rehash all the keys.  All other
  modifications to the dictionary are still off-limits during a
  PyDict_Next() iteration!

- New extended APIs related to passing compiler variables around.

- New abstract APIs PyObject_IsInstance(), PyObject_IsSubclass()
  implement isinstance() and issubclass().

- Py_BuildValue() now has a "D" conversion to create a Python complex
  number from a Py_complex C value.

- Extensions types which support weak references must now set the
  field allocated for the weak reference machinery to NULL themselves;
  this is done to avoid the cost of checking each object for having a
  weakly referencable type in PyObject_INIT(), since most types are
  not weakly referencable.

- PyFrame_FastToLocals() and PyFrame_LocalsToFast() copy bindings for
  free variables and cell variables to and from the frame's f_locals.

- Variants of several functions defined in pythonrun.h have been added
  to support the nested_scopes future statement.  The variants all end
  in Flags and take an extra argument, a PyCompilerFlags *; examples:
  PyRun_AnyFileExFlags(), PyRun_InteractiveLoopFlags().  These
  variants may be removed in Python 2.2, when nested scopes are
  mandatory.

Distutils

- the sdist command now writes a PKG-INFO file, as described in PEP 241,
  into the release tree.

- several enhancements to the bdist_wininst command from Thomas Heller
  (an uninstaller, more customization of the installer's display)

- from Jack Jansen: added Mac-specific code to generate a dialog for
  users to specify the command-line (because providing a command-line with
  MacPython is awkward).  Jack also made various fixes for the Mac
  and the Metrowerks compiler.

- added 'platforms' and 'keywords' to the set of metadata that can be
  specified for a distribution.

- applied patches from Jason Tishler to make the compiler class work with
  Cygwin.


What's New in Python 2.1 beta 1?
================================

Core language, builtins, and interpreter

- Following an outcry from the community about the amount of code
  broken by the nested scopes feature introduced in 2.1a2, we decided
  to make this feature optional, and to wait until Python 2.2 (or at
  least 6 months) to make it standard.  The option can be enabled on a
  per-module basis by adding "from __future__ import nested_scopes" at
  the beginning of a module (before any other statements, but after
  comments and an optional docstring).  See PEP 236 (Back to the
  __future__) for a description of the __future__ statement.  PEP 227
  (Statically Nested Scopes) has been updated to reflect this change,
  and to clarify the semantics in a number of endcases.

- The nested scopes code, when enabled, has been hardened, and most
  bugs and memory leaks in it have been fixed.

- Compile-time warnings are now generated for a number of conditions
  that will break or change in meaning when nested scopes are enabled:

  - Using "from...import *" or "exec" without in-clause in a function
    scope that also defines a lambda or nested function with one or
    more free (non-local) variables.  The presence of the import* or
    bare exec makes it impossible for the compiler to determine the
    exact set of local variables in the outer scope, which makes it
    impossible to determine the bindings for free variables in the
    inner scope.  To avoid the warning about import *, change it into
    an import of explicitly name object, or move the import* statement
    to the global scope; to avoid the warning about bare exec, use
    exec...in... (a good idea anyway -- there's a possibility that
    bare exec will be deprecated in the future).

  - Use of a global variable in a nested scope with the same name as a
    local variable in a surrounding scope.  This will change in
    meaning with nested scopes: the name in the inner scope will
    reference the variable in the outer scope rather than the global
    of the same name.  To avoid the warning, either rename the outer
    variable, or use a global statement in the inner function.

- An optional object allocator has been included.  This allocator is
  optimized for Python objects and should be faster and use less memory
  than the standard system allocator.  It is not enabled by default
  because of possible thread safety problems.  The allocator is only
  protected by the Python interpreter lock and it is possible that some
  extension modules require a thread safe allocator.  The object
  allocator can be enabled by providing the "--with-pymalloc" option to
  configure.

Standard library

- pyexpat now detects the expat version if expat.h defines it. A
  number of additional handlers are provided, which are only available
  since expat 1.95. In addition, the methods SetParamEntityParsing and
  GetInputContext of Parser objects are available with 1.95.x
  only. Parser objects now provide the ordered_attributes and
  specified_attributes attributes. A new module expat.model was added,
  which offers a number of additional constants if 1.95.x is used.

- xml.dom offers the new functions registerDOMImplementation and
  getDOMImplementation.

- xml.dom.minidom offers a toprettyxml method. A number of DOM
  conformance issues have been resolved. In particular, Element now
  has an hasAttributes method, and the handling of namespaces was
  improved.

- Ka-Ping Yee contributed two new modules: inspect.py, a module for
  getting information about live Python code, and pydoc.py, a module
  for interactively converting docstrings to HTML or text.
  Tools/scripts/pydoc, which is now automatically installed into
  /bin, uses pydoc.py to display documentation; try running
  "pydoc -h" for instructions.  "pydoc -g" pops up a small GUI that
  lets you browse the module docstrings using a web browser.

- New library module difflib.py, primarily packaging the SequenceMatcher
  class at the heart of the popular ndiff.py file-comparison tool.

- doctest.py (a framework for verifying Python code examples in docstrings)
  is now part of the std library.

Windows changes

- A new entry in the Start menu, "Module Docs", runs "pydoc -g" -- a
  small GUI that lets you browse the module docstrings using your
  default web browser.

- Import is now case-sensitive.  PEP 235 (Import on Case-Insensitive
  Platforms) is implemented.  See

      http://python.sourceforge.net/peps/pep-0235.html

  for full details, especially the "Current Lower-Left Semantics" section.
  The new Windows import rules are simpler than before:

  A. If the PYTHONCASEOK environment variable exists, same as
     before:  silently accept the first case-insensitive match of any
     kind; raise ImportError if none found.

  B. Else search sys.path for the first case-sensitive match; raise
     ImportError if none found.

  The same rules have been implented on other platforms with case-
  insensitive but case-preserving filesystems too (including Cygwin, and
  several flavors of Macintosh operating systems).

- winsound module:  Under Win9x, winsound.Beep() now attempts to simulate
  what it's supposed to do (and does do under NT and 2000) via direct
  port manipulation.  It's unknown whether this will work on all systems,
  but it does work on my Win98SE systems now and was known to be useless on
  all Win9x systems before.

- Build:  Subproject _test (effectively) renamed to _testcapi.

New platforms

- 2.1 should compile and run out of the box under MacOS X, even using HFS+.
  Thanks to Steven Majewski!

- 2.1 should compile and run out of the box on Cygwin.  Thanks to Jason
  Tishler!

- 2.1 contains new files and patches for RISCOS, thanks to Dietmar
  Schwertberger!  See RISCOS/README for more information -- it seems
  that because of the bizarre filename conventions on RISCOS, no port
  to that platform is easy.


What's New in Python 2.1 alpha 2?
=================================

Core language, builtins, and interpreter

- Scopes nest.  If a name is used in a function or class, but is not
  local, the definition in the nearest enclosing function scope will
  be used.  One consequence of this change is that lambda statements
  could reference variables in the namespaces where the lambda is
  defined.  In some unusual cases, this change will break code.

  In all previous version of Python, names were resolved in exactly
  three namespaces -- the local namespace, the global namespace, and
  the builtin namespace.  According to this old definition, if a
  function A is defined within a function B, the names bound in B are
  not visible in A.  The new rules make names bound in B visible in A,
  unless A contains a name binding that hides the binding in B.

  Section 4.1 of the reference manual describes the new scoping rules
  in detail.  The test script in Lib/test/test_scope.py demonstrates
  some of the effects of the change.

  The new rules will cause existing code to break if it defines nested
  functions where an outer function has local variables with the same
  name as globals or builtins used by the inner function.  Example:

    def munge(str):
        def helper(x):
            return str(x)
        if type(str) != type(''):
            str = helper(str)
        return str.strip()

  Under the old rules, the name str in helper() is bound to the
  builtin function str().  Under the new rules, it will be bound to
  the argument named str and an error will occur when helper() is
  called.

- The compiler will report a SyntaxError if "from ... import *" occurs
  in a function or class scope.  The language reference has documented
  that this case is illegal, but the compiler never checked for it.
  The recent introduction of nested scope makes the meaning of this
  form of name binding ambiguous.  In a future release, the compiler
  may allow this form when there is no possibility of ambiguity.

- repr(string) is easier to read, now using hex escapes instead of octal,
  and using \t, \n and \r instead of \011, \012 and \015 (respectively):

  >>> "\texample \r\n" + chr(0) + chr(255)
  '\texample \r\n\x00\xff'         # in 2.1
  '\011example \015\012\000\377'   # in 2.0

- Functions are now compared and hashed by identity, not by value, since
  the func_code attribute is writable.

- Weak references (PEP 205) have been added.  This involves a few
  changes in the core, an extension module (_weakref), and a Python
  module (weakref).  The weakref module is the public interface.  It
  includes support for "explicit" weak references, proxy objects, and
  mappings with weakly held values.

- A 'continue' statement can now appear in a try block within the body
  of a loop.  It is still not possible to use continue in a finally
  clause.

Standard library

- mailbox.py now has a new class, PortableUnixMailbox which is
  identical to UnixMailbox but uses a more portable scheme for
  determining From_ separators.  Also, the constructors for all the
  classes in this module have a new optional `factory' argument, which
  is a callable used when new message classes must be instantiated by
  the next() method.

- random.py is now self-contained, and offers all the functionality of
  the now-deprecated whrandom.py.  See the docs for details.  random.py
  also supports new functions getstate() and setstate(), for saving
  and restoring the internal state of the generator; and jumpahead(n),
  for quickly forcing the internal state to be the same as if n calls to
  random() had been made.  The latter is particularly useful for multi-
  threaded programs, creating one instance of the random.Random() class for
  each thread, then using .jumpahead() to force each instance to use a
  non-overlapping segment of the full period.

- random.py's seed() function is new.  For bit-for-bit compatibility with
  prior releases, use the whseed function instead.  The new seed function
  addresses two problems:  (1) The old function couldn't produce more than
  about 2**24 distinct internal states; the new one about 2**45 (the best
  that can be done in the Wichmann-Hill generator).  (2) The old function
  sometimes produced identical internal states when passed distinct
  integers, and there was no simple way to predict when that would happen;
  the new one guarantees to produce distinct internal states for all
  arguments in [0, 27814431486576L).

- The socket module now supports raw packets on Linux.  The socket
  family is AF_PACKET.

- test_capi.py is a start at running tests of the Python C API.  The tests
  are implemented by the new Modules/_testmodule.c.

- A new extension module, _symtable, provides provisional access to the
  internal symbol table used by the Python compiler.  A higher-level
  interface will be added on top of _symtable in a future release.

- Removed the obsolete soundex module.

- xml.dom.minidom now uses the standard DOM exceptions. Node supports
  the isSameNode method; NamedNodeMap the get method.

- xml.sax.expatreader supports the lexical handler property; it
  generates comment, startCDATA, and endCDATA events.

Windows changes

- Build procedure:  the zlib project is built in a different way that
  ensures the zlib header files used can no longer get out of synch with
  the zlib binary used.  See PCbuild\readme.txt for details.  Your old
  zlib-related directories can be deleted; you'll need to download fresh
  source for zlib and unpack it into a new directory.

- Build:  New subproject _test for the benefit of test_capi.py (see above).

- Build:  New subproject _symtable, for new DLL _symtable.pyd (a nascent
  interface to some Python compiler internals).

- Build:  Subproject ucnhash is gone, since the code was folded into the
  unicodedata subproject.

What's New in Python 2.1 alpha 1?
=================================

Core language, builtins, and interpreter

- There is a new Unicode companion to the PyObject_Str() API
  called PyObject_Unicode(). It behaves in the same way as the
  former, but assures that the returned value is an Unicode object
  (applying the usual coercion if necessary).

- The comparison operators support "rich comparison overloading" (PEP
  207).  C extension types can provide a rich comparison function in
  the new tp_richcompare slot in the type object.  The cmp() function
  and the C function PyObject_Compare() first try the new rich
  comparison operators before trying the old 3-way comparison.  There
  is also a new C API PyObject_RichCompare() (which also falls back on
  the old 3-way comparison, but does not constrain the outcome of the
  rich comparison to a Boolean result).

  The rich comparison function takes two objects (at least one of
  which is guaranteed to have the type that provid