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Python News

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(editors: check NEWS.help for information about editing NEWS using ReST.)

What's New in Python 2.3 alpha 2?

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

*Release date: XX-XXX-2003

Core and builtins

-----------------

Extension modules

-----------------

- fcntl now exposes the strops.h I_* constants.

Library

-------

Tools/Demos

-----------

Build

-----

C API

-----

New platforms

-------------

Tests

-----

Windows

-------

Mac

---

What's New in Python 2.3 alpha 1?

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

*Release date: 31-Dec-2002*

Type/class unification and new-style classes

--------------------------------------------

- One can now assign to __bases__ and __name__ of new-style classes.

- dict() now accepts keyword arguments so that dict(one=1, two=2)

is the equivalent of {"one": 1, "two": 2}. Accordingly,

the existing (but undocumented) 'items' keyword argument has

been eliminated. This means that dict(items=someMapping) now has

a different meaning than before.

- int() now returns a long object if the argument is outside the

integer range, so int("4"*1000), int(1e200) and int(1L<<1000) will

all return long objects instead of raising an OverflowError.

- Assignment to __class__ is disallowed if either the old or the new

class is a statically allocated type object (such as defined by an

extension module). This prevents anomalies like 2.__class__ = bool.

- New-style object creation and deallocation have been sped up

significantly; they are now faster than classic instance creation

and deallocation.

- The __slots__ variable can now mention "private" names, and the

right thing will happen (e.g. __slots__ = ["__foo"]).

- The built-ins slice() and buffer() are now callable types. The

types classobj (formerly class), code, function, instance, and

instancemethod (formerly instance-method), which have no built-in

names but are accessible through the types module, are now also

callable. The type dict-proxy is renamed to dictproxy.

- 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]

- Tightened the __slots__ rules: a slot name must be a valid Python

identifier.

- The constructor for the module type now requires a name argument and

takes an optional docstring argument. Previously, this constructor

ignored its arguments. As a consequence, deriving a class from a

module (not from the module type) is now illegal; previously this

created an unnamed module, just like invoking the module type did.

[SF bug 563060]

- A new type object, 'basestring', is added. This is a common base type

for 'str' and 'unicode', and can be used instead of

types.StringTypes, e.g. to test whether something is "a string":

isinstance(x, basestring) is True for Unicode and 8-bit strings. This

is an abstract base class and cannot be instantiated directly.

- 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]

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

- 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.)

Core and builtins

-----------------

- Import from zipfiles is now supported. The name of a zipfile placed

on sys.path causes the import statement to look for importable Python

modules (with .py, pyc and .pyo extensions) and packages inside the

zipfile. The zipfile import follows the specification (though not

the sample implementation) of PEP 273. The semantics of __path__ are

compatible with those that have been implemented in Jython since

Jython 2.1.

- PEP 302 has been accepted. Although it was inititally developed to

support zipimport, it offers a new, general import hook mechanism.

Several new variables have been added to the sys module:

sys.meta_path, sys.path_hooks, and sys.path_importer_cache; these

make extending the import statement much more convenient than

overriding the __import__ built-in function. For a description of

these, see PEP 302.

- A frame object's f_lineno attribute can now be written to from a

trace function to change which line will execute next. A command to

exploit this from pdb has been added. [SF patch #643835]

- The _codecs support module for codecs.py was turned into a builtin

module to assure that at least the builtin codecs are available

to the Python parser for source code decoding according to PEP 263.

- issubclass now supports a tuple as the second argument, just like

isinstance does. ``issubclass(X, (A, B))`` is equivalent to

``issubclass(X, A) or issubclass(X, B)``.

- Thanks to Armin Rigo, the last known way to provoke a system crash

by cleverly arranging for a comparison function to mutate a list

during a list.sort() operation has been fixed. The effect of

attempting to mutate a list, or even to inspect its contents or

length, while a sort is in progress, is not defined by the language.

The C implementation of Python 2.3 attempts to detect mutations,

and raise ValueError if one occurs, but there's no guarantee that

all mutations will be caught, or that any will be caught across

releases or implementations.

- Unicode file name processing for Windows (PEP 277) is implemented.

All platforms now have an os.path.supports_unicode_filenames attribute,

which is set to True on Windows NT/2000/XP, and False elsewhere.

- Codec error handling callbacks (PEP 293) are implemented.

Error handling in unicode.encode or str.decode can now be customized.

- A subtle change to the semantics of the built-in function intern():

interned strings are no longer immortal. You must keep a reference

to the return value intern() around to get the benefit.

- Use of 'None' as a variable, argument or attribute name now

issues a SyntaxWarning. In the future, None may become a keyword.

- SET_LINENO is gone. co_lnotab is now consulted to determine when to

call the trace function. C code that accessed f_lineno should call

PyCode_Addr2Line instead (f_lineno is still there, but only kept up

to date when there is a trace function set).

- There's a new warning category, FutureWarning. This is used to warn

about a number of situations where the value or sign of an integer

result will change in Python 2.4 as a result of PEP 237 (integer

unification). The warnings implement stage B0 mentioned in that

PEP. The warnings are about the following situations:

- Octal and hex literals without 'L' prefix in the inclusive range

[0x80000000..0xffffffff]; these are currently negative ints, but

in Python 2.4 they will be positive longs with the same bit

pattern.

- Left shifts on integer values that cause the outcome to lose

bits or have a different sign than the left operand. To be

precise: x<<n where this currently doesn't yield the same value

as long(x)<<n; in Python 2.4, the outcome will be long(x)<<n.

- Conversions from ints to string that show negative values as

unsigned ints in the inclusive range [0x80000000..0xffffffff];

this affects the functions hex() and oct(), and the string

formatting codes %u, %o, %x, and %X. In Python 2.4, these will

show signed values (e.g. hex(-1) currently returns "0xffffffff";

in Python 2.4 it will return "-0x1").

- The bits manipulated under the cover by sys.setcheckinterval() have

been changed. Both the check interval and the ticker used to be

per-thread values. They are now just a pair of global variables.

In addition, the default check interval was boosted from 10 to 100

bytecode instructions. This may have some effect on systems that

relied on the old default value. In particular, in multi-threaded

applications which try to be highly responsive, response time will

increase by some (perhaps imperceptible) amount.

- When multiplying very large integers, a version of the so-called

Karatsuba algorithm is now used. This is most effective if the

inputs have roughly the same size. If they both have about N digits,

Karatsuba multiplication has O(N**1.58) runtime (the exponent is

log_base_2(3)) instead of the previous O(N**2). Measured results may

be better or worse than that, depending on platform quirks. Besides

the O() improvement in raw instruction count, the Karatsuba algorithm

appears to have much better cache behavior on extremely large integers

(starting in the ballpark of a million bits). Note that this is a

simple implementation, and there's no intent here to compete with,

e.g., GMP. It gives a very nice speedup when it applies, but a package

devoted to fast large-integer arithmetic should run circles around it.

- u'%c' will now raise a ValueError in case the argument is an

integer outside the valid range of Unicode code point ordinals.

- The tempfile module has been overhauled for enhanced security. The

mktemp() function is now deprecated; new, safe replacements are

mkstemp() (for files) and mkdtemp() (for directories), and the

higher-level functions NamedTemporaryFile() and TemporaryFile().

Use of some global variables in this module is also deprecated; the

new functions have keyword arguments to provide the same

functionality. All Lib, Tools and Demo modules that used the unsafe

interfaces have been updated to use the safe replacements. Thanks

to Zack Weinberg!

- 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.

- Previously, "str1 in str2" required str1 to be a string of length 1.

This restriction has been relaxed to allow str1 to be a string of

any length. Thus "'el' in 'hello world'" returns True now.

- File objects are now their own iterators. For a file f, iter(f) now

returns f (unless f is closed), and f.next() is similar to

f.readline() when EOF is not reached; however, f.next() uses a

readahead buffer that messes up the file position, so mixing

f.next() and f.readline() (or other methods) doesn't work right.

Calling f.seek() drops the readahead buffer, but other operations

don't. It so happens that this gives a nice additional speed boost

to "for line in file:"; the xreadlines method and corresponding

module are now obsolete. Thanks to Oren Tirosh!

- Encoding declarations (PEP 263, phase 1) have been implemented. A

comment of the form "# -*- coding: <encodingname> -*-" in the first

or second line of a Python source file indicates the encoding.

- list.sort() has a new implementation. While cross-platform results

may vary, and in data-dependent ways, this is much faster on many

kinds of partially ordered lists than the previous implementation,

and reported to be just as fast on randomly ordered lists on

several major platforms. This sort is also stable (if A==B and A

precedes B in the list at the start, A precedes B after the sort too),

although the language definition does not guarantee stability. A

potential drawback is that list.sort() may require temp space of

len(list)*2 bytes (``*4`` on a 64-bit machine). It's therefore possible

for list.sort() to raise MemoryError now, even if a comparison function

does not. See <http://www.python.org/sf/587076> for full details.

- All standard iterators now ensure that, once StopIteration has been

raised, all future calls to next() on the same iterator will also

raise StopIteration. There used to be various counterexamples to

this behavior, which could caused confusion or subtle program

breakage, without any benefits. (Note that this is still an

iterator's responsibility; the iterator framework does not enforce

this.)

- Ctrl+C handling on Windows has been made more consistent with

other platforms. KeyboardInterrupt can now reliably be caught,

and Ctrl+C at an interactive prompt no longer terminates the

process under NT/2k/XP (it never did under Win9x). Ctrl+C will

interrupt time.sleep() in the main thread, and any child processes

created via the popen family (on win2k; we can't make win9x work

reliably) are also interrupted (as generally happens on for Linux/Unix.)

[SF bugs 231273, 439992 and 581232]

- sys.getwindowsversion() has been added on Windows. This

returns a tuple with information about the version of Windows

currently running.

- Slices and repetitions of buffer objects now consistently return

a string. Formerly, strings would be returned most of the time,

but a buffer object would be returned when the repetition count

was one or when the slice range was all inclusive.

- Unicode objects in sys.path are no longer ignored but treated

as directory names.

- Fixed string.startswith and string.endswith builtin methods

so they accept negative indices. [SF bug 493951]

- Fixed a bug with a continue inside a try block and a yield in the

finally clause. [SF bug 567538]

- Most builtin sequences now support "extended slices", i.e. slices

with a third "stride" parameter. For example, "hello world"[::-1]

gives "dlrow olleh".

- A new warning PendingDeprecationWarning was added to provide

direction on features which are in the process of being deprecated.

The warning will not be printed by default. To see the pending

deprecations, use -Walways::PendingDeprecationWarning::

as a command line option or warnings.filterwarnings() in code.

- Deprecated features of xrange objects have been removed as

promised. The start, stop, and step attributes and the tolist()

method no longer exist. xrange repetition and slicing have been

removed.

- New builtin function enumerate(x), from PEP 279. Example:

enumerate("abc") is an iterator returning (0,"a"), (1,"b"), (2,"c").

The argument can be an arbitrary iterable object.

- The assert statement no longer tests __debug__ at runtime. This means

that assert statements cannot be disabled by assigning a false value

to __debug__.

- 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".

- There's a new dictionary constructor (a class method of the dict

class), dict.fromkeys(iterable, value=None). It constructs a

dictionary with keys taken from the iterable and all values set to a

single value. It can be used for building sets and for removing

duplicates from sequences.

- Added a new dict method pop(key). This removes and returns the

value corresponding to key. [SF patch #539949]

- A new built-in type, bool, has been added, as well as built-in

names for its two values, True and False. Comparisons and sundry

other operations that return a truth value have been changed to

return a bool instead. Read PEP 285 for an explanation of why this

is backward compatible.

- 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.

- The optional object allocator ("pymalloc") has been enabled by

default. The recommended practice for memory allocation and

deallocation has been streamlined. A header file is included,

Misc/pymemcompat.h, which can be bundled with 3rd party extensions

and lets them use the same API with Python versions from 1.5.2

onwards.

- PyErr_Display will provide file and line information for all exceptions

that have an attribute print_file_and_line, not just SyntaxErrors.

- The UTF-8 codec will now encode and decode Unicode surrogates

correctly and without raising exceptions for unpaired ones.

- Universal newlines (PEP 278) is implemented. Briefly, using 'U'

instead of 'r' when opening a text file for reading changes the line

ending convention so that any of '\r', '\r\n', and '\n' is

recognized (even mixed in one file); all three are converted to

'\n', the standard Python line end character.

- file.xreadlines() now raises a ValueError if the file is closed:

Previously, an xreadlines object was returned which would raise

a ValueError when the xreadlines.next() method was called.

- sys.exit() inadvertently allowed more than one argument.

An exception will now be raised if more than one argument is used.

- Changed evaluation order of dictionary literals to conform to the

general left to right evaluation order rule. Now {f1(): f2()} will

evaluate f1 first.

- Fixed bug #521782: when a file was in non-blocking mode, file.read()

could silently lose data or wrongly throw an unknown error.

- The sq_repeat, sq_inplace_repeat, sq_concat and sq_inplace_concat

slots are now always tried after trying the corresponding nb_* slots.

This fixes a number of minor bugs (see bug #624807).

Extension modules

-----------------

- posix.openpty now works on all systems that have /dev/ptmx.

- A module zipimport exists to support importing code from zip

archives.

- The new datetime module supplies classes for manipulating dates and

times. The basic design came from the Zope "fishbowl process", and

favors practical commercial applications over calendar esoterica. See

http://www.zope.org/Members/fdrake/DateTimeWiki/FrontPage

- _tkinter now returns Tcl objects, instead of strings. Objects which

have Python equivalents are converted to Python objects, other objects

are wrapped. This can be configured through the wantobjects method,

or Tkinter.wantobjects.

- The PyBSDDB wrapper around the Sleepycat Berkeley DB library has

been added as the package bsddb. The traditional bsddb module is

still available in source code, but not built automatically anymore,

and is now named bsddb185. This supports Berkeley DB versions from

3.0 to 4.1.

- unicodedata was updated to Unicode 3.2. It supports normalization

and names for Hangul syllables and CJK unified ideographs.

- resource.getrlimit() now returns longs instead of ints.

- readline now dynamically adjusts its input/output stream if

sys.stdin/stdout changes.

- The _tkinter module (and hence Tkinter) has dropped support for

Tcl/Tk 8.0 and 8.1. Only Tcl/Tk versions 8.2, 8.3 and 8.4 are

supported.

- cPickle.BadPickleGet is now a class.

- The time stamps in os.stat_result are floating point numbers

after stat_float_times has been called.

- If the size passed to mmap.mmap() is larger than the length of the

file on non-Windows platforms, a ValueError is raised. [SF bug 585792]

- The xreadlines module is slated for obsolescence.

- The strptime function in the time module is now always available (a

Python implementation is used when the C library doesn't define it).

- The 'new' module is no longer an extension, but a Python module that

only exists for backwards compatibility. Its contents are no longer

functions but callable type objects.

- The bsddb.*open functions can now take 'None' as a filename.

This will create a temporary in-memory bsddb that won't be

written to disk.

- posix.getloadavg, posix.lchown, posix.killpg, posix.mknod, and

posix.getpgid have been added where available.

- The locale module now exposes the C library's gettext interface. It

also has a new function getpreferredencoding.

- 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 now ships with zlib-1.1.4.

- pwd, grp, and resource return enhanced tuples now, with symbolic

field names.

- array.array is now a type object. A new format character

'u' indicates Py_UNICODE arrays. For those, .tounicode and

.fromunicode methods are available. Arrays now support __iadd__

and __imul__.

- dl now builds on every system that has dlfcn.h. Failure in case

of sizeof(int)!=sizeof(long)!=sizeof(void*) is delayed until dl.open

is called.

- signal.sigpending, signal.sigprocmask and signal.sigsuspend have

been added where available.

- The sys module acquired a new attribute, api_version, which evaluates

to the value of the PYTHON_API_VERSION macro with which the

interpreter was compiled.

- Fixed bug #470582: sre module would return a tuple (None, 'a', 'ab')

when applying the regular expression '^((a)c)?(ab)$' on 'ab'. It now

returns (None, None, 'ab'), as expected. Also fixed handling of

lastindex/lastgroup match attributes in similar cases. For example,

when running the expression r'(a)(b)?b' over 'ab', lastindex must be

1, not 2.

- Fixed bug #581080: sre scanner was not checking the buffer limit

before increasing the current pointer. This was creating an infinite

loop in the search function, once the pointer exceeded the buffer

limit.

- The os.fdopen function now enforces a file mode starting with the

letter 'r', 'w' or 'a', otherwise a ValueError is raised. This fixes

bug #623464.

Library

-------

- Freeze's modulefinder.py has been moved to the standard library;

slightly improved so it will issue less false missing submodule

reports (see sf path #643711 for details). Documentation will follow

with Python 2.3a2.

- os.path exposes getctime.

- unittest.py now has two additional methods called assertAlmostEqual()

and failIfAlmostEqual(). They implement an approximate comparision

by rounding the difference between the two arguments and comparing

the result to zero. Approximate comparision is essential for

unit tests of floating point results.

- calendar.py now depends on the new datetime module rather than

the time module. As a result, the range of allowable dates

has been increased.

- pdb has a new 'j(ump)' command to select the next line to be

executed.

- The distutils created windows installers now can run a

postinstallation script.

- doctest.testmod can now be called without argument, which means to

test the current module.

- When cancelling a server that implemented threading with a keyboard

interrupt, the server would shut down but not terminate (waiting on

client threads). A new member variable, daemon_threads, was added to

the ThreadingMixIn class in SocketServer.py to make it explicit that

this behavior needs to be controlled.

- A new module, optparse, provides a fancy alternative to getopt for

command line parsing. It is a slightly modified version of Greg

Ward's Optik package.

- UserDict.py now defines a DictMixin class which defines all dictionary

methods for classes that already have a minimum mapping interface.

This greatly simplifies writing classes that need to be substitutable

for dictionaries (such as the shelve module).

- shelve.py now subclasses from UserDict.DictMixin. Now shelve supports

all dictionary methods. This eases the transition to persistent

storage for scripts originally written with dictionaries in mind.

- shelve.open and the various classes in shelve.py now accept an optional

binary flag, which defaults to False. If True, the values stored in the

shelf are binary pickles.

- A new package, logging, implements the logging API defined by PEP

282. The code is written by Vinay Sajip.

- StreamReader, StreamReaderWriter and StreamRecoder in the codecs

modules are iterators now.

- gzip.py now handles files exceeding 2GB. Files over 4GB also work

now (provided the OS supports it, and Python is configured with large

file support), but in that case the underlying gzip file format can

record only the least-significant 32 bits of the file size, so that

some tools working with gzipped files may report an incorrect file

size.

- xml.sax.saxutils.unescape has been added, to replace entity references

with their entity value.

- Queue.Queue.{put,get} now support an optional timeout argument.

- Various features of Tk 8.4 are exposed in Tkinter.py. The multiple

option of tkFileDialog is exposed as function askopenfile{,name}s.

- Various configure methods of Tkinter have been stream-lined, so that

tag_configure, image_configure, window_configure now return a

dictionary when invoked with no argument.

- Importing the readline module now no longer has the side effect of

calling setlocale(LC_CTYPE, ""). The initial "C" locale, or

whatever locale is explicitly set by the user, is preserved. If you

want repr() of 8-bit strings in your preferred encoding to preserve

all printable characters of that encoding, you have to add the

following code to your $PYTHONSTARTUP file or to your application's

main():

import locale

locale.setlocale(locale.LC_CTYPE, "")

- shutil.move was added. shutil.copytree now reports errors as an

exception at the end, instead of printing error messages.

- Encoding name normalization was generalized to not only

replace hyphens with underscores, but also all other non-alphanumeric

characters (with the exception of the dot which is used for Python

package names during lookup). The aliases.py mapping was updated

to the new standard.

- mimetypes has two new functions: guess_all_extensions() which

returns a list of all known extensions for a mime type, and

add_type() which adds one mapping between a mime type and

an extension to the database.

- New module: sets, defines the class Set that implements a mutable

set type using the keys of a dict to represent the set. There's

also a class ImmutableSet which is useful when you need sets of sets

or when you need to use sets as dict keys, and a class BaseSet which

is the base class of the two.

- Added operator.pow(a,b) which is equivalent to a**b.

- Added random.sample(population,k) for random sampling without replacement.

Returns a k length list of unique elements chosen from the population.

- random.randrange(-sys.maxint-1, sys.maxint) no longer raises

OverflowError. That is, it now accepts any combination of 'start'

and 'stop' arguments so long as each is in the range of Python's

bounded integers.

- Thanks to Raymond Hettinger, random.random() now uses a new core

generator. The Mersenne Twister algorithm is implemented in C,

threadsafe, faster than the previous generator, has an astronomically

large period (2**19937-1), creates random floats to full 53-bit

precision, and may be the most widely tested random number generator

in existence.

The random.jumpahead(n) method has different semantics for the new

generator. Instead of jumping n steps ahead, it uses n and the

existing state to create a new state. This means that jumpahead()

continues to support multi-threaded code needing generators of

non-overlapping sequences. However, it will break code which relies

on jumpahead moving a specific number of steps forward.

The attributes random.whseed and random.__whseed have no meaning for

the new generator. Code using these attributes should switch to a

new class, random.WichmannHill which is provided for backward

compatibility and to make an alternate generator available.

- New "algorithms" module: heapq, implements a heap queue. Thanks to

Kevin O'Connor for the code and François Pinard for an entertaining

write-up explaining the theory and practical uses of heaps.

- New encoding for the Palm OS character set: palmos.

- binascii.crc32() and the zipfile module had problems on some 64-bit

platforms. These have been fixed. On a platform with 8-byte C longs,

crc32() now returns a signed-extended 4-byte result, so that its value

as a Python int is equal to the value computed a 32-bit platform.

- xml.dom.minidom.toxml and toprettyxml now take an optional encoding

argument.

- Some fixes in the copy module: 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].

- Sockets now support timeout mode. After s.settimeout(T), where T is

a float expressing seconds, subsequent operations raise an exception

if they cannot be completed within T seconds. To disable timeout

mode, use s.settimeout(None). There's also a module function,

socket.setdefaulttimeout(T), which sets the default for all sockets

created henceforth.

- getopt.gnu_getopt was added. This supports GNU-style option

processing, where options can be mixed with non-option arguments.

- Stop using strings for exceptions. String objects used for

exceptions are now classes deriving from Exception. The objects

changed were: Tkinter.TclError, bdb.BdbQuit, macpath.norm_error,

tabnanny.NannyNag, and xdrlib.Error.

- Constants BOM_UTF8, BOM_UTF16, BOM_UTF16_LE, BOM_UTF16_BE,

BOM_UTF32, BOM_UTF32_LE and BOM_UTF32_BE that represent the Byte

Order Mark in UTF-8, UTF-16 and UTF-32 encodings for little and

big endian systems were added to the codecs module. The old names

BOM32_* and BOM64_* were off by a factor of 2.

- Added conversion functions math.degrees() and math.radians().

- math.log() now takes an optional argument: math.log(x[, base]).

- ftplib.retrlines() now tests for callback is None rather than testing

for False. Was causing an error when given a callback object which

was callable but also returned len() as zero. The change may

create new breakage if the caller relied on the undocumented behavior

and called with callback set to [] or some other False value not

identical to None.

- random.gauss() 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 pickle.Pickler class grew a clear_memo() method to mimic that

provided by cPickle.Pickler.

- difflib's SequenceMatcher class now does a dynamic analysis of

which elements are so frequent as to constitute noise. For

comparing files as sequences of lines, this generally works better

than the IS_LINE_JUNK function, and function ndiff's linejunk

argument defaults to None now as a result. A happy benefit is

that SequenceMatcher may run much faster now when applied

to large files with many duplicate lines (for example, C program

text with lots of repeated "}" and "return NULL;" lines).

- New Text.dump() method in Tkinter module.

- New distutils commands for building packagers were added to

support pkgtool on Solaris and swinstall on HP-UX.

- distutils now has a new abstract binary packager base class

command/bdist_packager, which simplifies writing packagers.

This will hopefully provide the missing bits to encourage

people to submit more packagers, e.g. for Debian, FreeBSD

and other systems.

- The UTF-16, -LE and -BE stream readers now raise a

NotImplementedError for all calls to .readline(). Previously, they

used to just produce garbage or fail with an encoding error --

UTF-16 is a 2-byte encoding and the C lib's line reading APIs don't

work well with these.

- compileall now supports quiet operation.

- The BaseHTTPServer now implements optional HTTP/1.1 persistent

connections.

- socket module: the SSL support was broken out of the main

_socket module C helper and placed into a new _ssl helper

which now gets imported by socket.py if available and working.

- encodings package: added aliases for all supported IANA character

sets

- ftplib: to safeguard the user's privacy, anonymous login will use

"anonymous@" as default password, rather than the real user and host

name.

- 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.

- gettext.translation has an optional fallback argument, and

gettext.find an optional all argument. Translations will now fallback

on a per-message basis. The module supports plural forms, by means

of gettext.[d]ngettext and Translation.[u]ngettext.

- distutils bdist commands now offer a --skip-build option.

- warnings.warn now accepts a Warning instance as first argument.

- 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]

- The email.Parser.Parser class now properly parses strings regardless

of their line endings, which can be any of \r, \n, or \r\n (CR, LF,

or CRLF). Also, the Header class's constructor default arguments

has changed slightly so that an explicit maxlinelen value is always

honored, and so unicode conversion error handling can be specified.

- distutils' build_ext command now links c++ extensions with the c++

compiler available in the Makefile or CXX environment variable, if

running under *nix.

- New module bz2: provides a comprehensive interface for the bz2 compression

library. It implements a complete file interface, one-shot (de)compression

functions, and types for sequential (de)compression.

- New pdb command `pp' which is like `p' except that it pretty-prints

the value of its expression argument.

- Now bdist_rpm distutils command understands a verify_script option in

the config file, including the contents of the referred filename in

the "%verifyscript" section of the rpm spec file.

- Fixed bug #495695: webbrowser module would run graphic browsers in a

unix environment even if DISPLAY was not set. Also, support for

skipstone browser was included.

- Fixed bug #636769: rexec would run unallowed code if subclasses of

strings were used as parameters for certain functions.

Tools/Demos

-----------

- pygettext.py now supports globbing on Windows, and accepts module

names in addition to accepting file names.

- The SGI demos (Demo/sgi) have been removed. Nobody thought they

were interesting any more. (The SGI library modules and extensions

are still there; it is believed that at least some of these are

still used and useful.)

- IDLE supports the new encoding declarations (PEP 263); it can also

deal with legacy 8-bit files if they use the locale's encoding. It

allows non-ASCII strings in the interactive shell and executes them

in the locale's encoding.

- freeze.py now produces binaries which can import shared modules,

unlike before when this failed due to missing symbol exports in

the generated binary.

Build

-----

- On Unix, IDLE is now installed automatically.

- The fpectl module is not built by default; it's dangerous or useless

except in the hands of experts.

- The public Python C API will generally be declared using PyAPI_FUNC

and PyAPI_DATA macros, while Python extension module init functions

will be declared with PyMODINIT_FUNC. DL_EXPORT/DL_IMPORT macros

are deprecated.

- 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.

- Compiling out the cyclic garbage collector is no longer an option.

The old symbol WITH_CYCLE_GC is now ignored, and Python.h arranges

that it's always defined (for the benefit of any extension modules

that may be conditionalizing on it). A bonus is that any extension

type participating in cyclic gc can choose to participate in the

Py_TRASHCAN mechanism now too; in the absence of cyclic gc, this used

to require editing the core to teach the trashcan mechanism about the

new type.

- According to Annex F of the current C standard,

The Standard C macro HUGE_VAL and its float and long double analogs,

HUGE_VALF and HUGE_VALL, expand to expressions whose values are

positive infinities.

Python only uses the double HUGE_VAL, and only to #define its own symbol

Py_HUGE_VAL. Some platforms have incorrect definitions for HUGE_VAL.

pyport.h used to try to worm around that, but the workarounds triggered

other bugs on other platforms, so we gave up. If your platform defines

HUGE_VAL incorrectly, you'll need to #define Py_HUGE_VAL to something

that works on your platform. The only instance of this I'm sure about

is on an unknown subset of Cray systems, described here:

http://www.cray.com/swpubs/manuals/SN-2194_2.0/html-SN-2194_2.0/x3138.htm

Presumably 2.3a1 breaks such systems. If anyone uses such a system, help!

- The configure option --without-doc-strings can be used to remove the

doc strings from the builtin functions and modules; this reduces the

size of the executable.

- The universal newlines option (PEP 278) is on by default. On Unix

it can be disabled by passing --without-universal-newlines to the

configure script. On other platforms, remove

WITH_UNIVERSAL_NEWLINES from pyconfig.h.

- On Unix, a shared libpython2.3.so can be created with --enable-shared.

- All uses of the CACHE_HASH, INTERN_STRINGS, and DONT_SHARE_SHORT_STRINGS

preprocessor symbols were eliminated. The internal decisions they

controlled stopped being experimental long ago.

- The tools used to build the documentation now work under Cygwin as

well as Unix.

- The bsddb and dbm module builds have been changed to try and avoid version

skew problems and disable linkage with Berkeley DB 1.85 unless the

installer knows what s/he's doing. See the section on building these

modules in the README file for details.

C API

-----

- PyNumber_Check() now returns true for string and unicode objects.

This is a result of these types having a partially defined

tp_as_number slot. (This is not a feature, but an indication that

PyNumber_Check() is not very useful to determine numeric behavior.

It may be deprecated.)

- The string object's layout has changed: the pointer member

ob_sinterned has been replaced by an int member ob_sstate. On some

platforms (e.g. most 64-bit systems) this may change the offset of

the ob_sval member, so as a precaution the API_VERSION has been

incremented. The apparently unused feature of "indirect interned

strings", supported by the ob_sinterned member, is gone. Interned

strings are now usually mortal; theres a new API,

PyString_InternImmortal() that creates immortal interned strings.

(The ob_sstate member can only take three values; however, while

making it a char saves a few bytes per string object on average, in

it also slowed things down a bit because ob_sval was no longer

aligned.)

- The Py_InitModule*() functions now accept NULL for the 'methods'

argument. Modules without global functions are becoming more common

now that factories can be types rather than functions.

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

level.

- New functions PyErr_SetExcFromWindowsErr() and

PyErr_SetExcFromWindowsErrWithFilename(). Similar to

PyErr_SetFromWindowsErrWithFilename() and

PyErr_SetFromWindowsErr(), but they allow to specify

the exception type to raise. Available on Windows.

- Py_FatalError() is now declared as taking a const char* argument. It

was previously declared without const. This should not affect working

code.

- Added new macro PySequence_ITEM(o, i) that directly calls

sq_item without rechecking that o is a sequence and without

adjusting for negative indices.

- PyRange_New() now raises ValueError if the fourth argument is not 1.

This is part of the removal of deprecated features of the xrange

object.

- PyNumber_Coerce() and PyNumber_CoerceEx() now also invoke the type's

coercion if both arguments have the same type but this type has the

CHECKTYPES flag set. This is to better support proxies.

- The type of tp_free has been changed from "``void (*)(PyObject *)``" to

"``void (*)(void *)``".

- PyObject_Del, PyObject_GC_Del are now functions instead of macros.

- 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.

- The PyCore_* family of APIs have been removed.

- The "u#" parser marker will now pass through Unicode objects as-is

without going through the buffer API.

- The enumerators of cmp_op have been renamed to use the prefix ``PyCmp_``.

- An old #define of ANY as void has been removed from pyport.h. This

hasn't been used since Python's pre-ANSI days, and the #define has

been marked as obsolete since then. SF bug 495548 says it created

conflicts with other packages, so keeping it around wasn't harmless.

- Because Python's magic number scheme broke on January 1st, we decided

to stop Python development. Thanks for all the fish!

- Some of us don't like fish, so we changed Python's magic number

scheme to a new one. See Python/import.c for details.

New platforms

-------------

- OpenVMS is now supported.

- AtheOS is now supported.

- the EMX runtime environment on OS/2 is now supported.

- GNU/Hurd is now supported.

Tests

-----

- The regrtest.py script's -u option now provides a way to say "allow

all resources except this one." For example, to allow everything

except bsddb, give the option '-uall,-bsddb'.

Windows

-------

- The Windows distribution now ships with version 4.0.14 of the

Sleepycat Berkeley database library. This should be a huge

improvement over the previous Berkeley DB 1.85, which had many

bugs.

XXX What are the licensing issues here?

XXX If a user has a database created with a previous verion of

XXX Python, what must they do to convert it?

XXX I'm still not sure how to link this thing (see PCbuild/readme.txt).

XXX The version # is likely to change before 2.3a1.

- The Windows distribution now ships with a Secure Sockets Library (SLL)

module (_ssl.pyd)

- The Windows distribution now ships with Tcl/Tk version 8.4.1 (it

previously shipped with Tcl/Tk 8.3.2).

- When Python is built under a Microsoft compiler, sys.version now

includes the compiler version number (_MSC_VER). For example, under

MSVC 6, sys.version constains the substring "MSC v.1200 ". 1200 is

the value of _MSC_VER under MSVC 6.