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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

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

- long(string, base) takes time linear in len(string) when base is a power

of 2 now. It used to take time quadratic in len(string).

- filter returns now Unicode results for Unicode arguments.

- raw_input can now return Unicode objects.

- List objects' sort() method now accepts None as the comparison function.

Passing None is semantically identical to calling sort() with no

arguments.

- Fixed crash when printing a subclass of str and __str__ returned self.

See SF bug #667147.

- Fixed an invalid RuntimeWarning and an undetected error when trying

to convert a long integer into a float which couldn't fit.

See SF bug #676155.

Extension modules

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

- Added an itertools module containing high speed, memory efficient

looping constructs inspired by tools from Haskell and SML.

- The SSL module now handles sockets with a timeout set correctly (SF

patch #675750, fixing SF bug #675552).

- A new module _iconv_codec has been added, to expose the iconv(3)

library.

- os/posixmodule has grown the sysexits.h constants (EX_OK and friends).

- Fixed broken threadstate swap in readline that could cause fatal

errors when a readline hook was being invoked while a background

thread was active. (SF bugs #660476 and #513033.)

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

- Fix a crash on Solaris that occurred when calling close() on

an mmap'ed file which was already closed. (SF patch #665913)

- datetime changes:

The datetime and datetimetz classes have been collapsed into a single

datetime class, and likewise the time and timetz classes into a single

time class. Previously, a datetimetz object with tzinfo=None acted

exactly like a datetime object, and similarly for timetz. This wasn't

enough of a difference to justify distinct classes, and life is simpler

now.

today() and now() now round system timestamps to the closest

microsecond <http://www.python.org/sf/661086>. This repairs an

irritation most likely seen on Windows systems.

In dt.astimezone(tz), if tz.utcoffset(dt) returns a duration,

ValueError is raised if tz.dst(dt) returns None (2.3a1 treated it

as 0 instead, but a tzinfo subclass wishing to participate in

time zone conversion has to take a stand on whether it supports

DST; if you don't care about DST, then code dst() to return 0 minutes,

meaning that DST is never in effect).

The tzinfo methods utcoffset() and dst() must return a timedelta object

(or None) now. In 2.3a1 they could also return an int or long, but that

was an unhelpfully redundant leftover from an earlier version wherein

they couldn't return a timedelta. TOOWTDI.

The example tzinfo class for local time had a bug. It was replaced

by a later example coded by Guido.

datetime.astimezone(tz) no longer raises an exception when the

input datetime has no UTC equivalent in tz. For typical "hybrid" time

zones (a single tzinfo subclass modeling both standard and daylight

time), this case can arise one hour per year, at the hour daylight time

ends. See new docs for details. In short, the new behavior mimics

the local wall clock's behavior of repeating an hour in local time.

dt.astimezone() can no longer be used to convert between naive and aware

datetime objects. If you merely want to attach, or remove, a tzinfo

object, without any conversion of date and time members, use

dt.replace(tzinfo=whatever) instead, where "whatever" is None or a

tzinfo subclass instance.

A new method tzinfo.fromutc(dt) can be overridden in tzinfo subclasses

to give complete control over how a UTC time is to be converted to

a local time. The default astimezone() implementation calls fromutc()

as its last step, so a tzinfo subclass can affect that too by overriding

fromutc(). It's expected that the default fromutc() implementation will

be suitable as-is for "almost all" time zone subclasses, but the

creativity of political time zone fiddling appears unbounded -- fromutc()

allows the highly motivated to emulate any scheme expressible in Python.

datetime.now(): The optional tzinfo argument was undocumented (that's

repaired), and its name was changed to tz ("tzinfo" is overloaded enough

already). With a tz argument, now(tz) used to return the local date

and time, and attach tz to it, without any conversion of date and time

members. This was less than useful. Now now(tz) returns the current

date and time as local time in tz's time zone, akin to

tz.fromutc(datetime.utcnow().replace(tzinfo=utc))

where "utc" is an instance of a tzinfo subclass modeling UTC. Without

a tz argument, now() continues to return the current local date and time,

as a naive datetime object.

datetime.fromtimestamp(): Like datetime.now() above, this had less than

useful behavior when the optional tinzo argument was specified. See

also SF bug report <http://www.python.org/sf/660872>.

date and datetime comparison: In order to prevent comparison from

falling back to the default compare-object-addresses strategy, these

raised TypeError whenever they didn't understand the other object type.

They still do, except when the other object has a "timetuple" attribute,

in which case they return NotImplemented now. This gives other

datetime objects (e.g., mxDateTime) a chance to intercept the

comparison.

The constructors building a datetime from a timestamp could raise

ValueError if the platform C localtime()/gmtime() inserted "leap

seconds". Leap seconds are ignored now. On such platforms, it's

possible to have timestamps that differ by a second, yet where

datetimes constructed from them are equal.

The pickle format of date, time and datetime objects has changed

completely. The undocumented pickler and unpickler functions no

longer exist. The undocumented __setstate__() and __getstate__()

methods no longer exist either.

Library

-------

- The new pickletools.py contains lots of documentation about pickle

internals, and supplies some helpers for working with pickles, such as

a symbolic pickle disassembler.

- Xmlrpclib.py now supports the builtin boolean type.

- py_compile has a new 'doraise' flag and a new PyCompileError

exception.

- SimpleXMLRPCServer now supports CGI through the CGIXMLRPCRequestHandler

class.

- The sets module now raises TypeError in __cmp__, to clarify that

sets are not intended to be three-way-compared; the comparison

operators are overloaded as subset/superset tests.

- Bastion.py and rexec.py are disabled. These modules are not safe in

Python 2.2. or 2.3.

- realpath is now exported when doing from poxixpath import *.

It is also exported for ntpath, macpath, and os2emxpath.

See SF bug #659228.

- New module tarfile from Lars Gustäbel provides a comprehensive interface

to tar archive files with transparent gzip and bzip2 compression.

See SF patch #651082.

- urlparse can now parse imap:// URLs. See SF feature request #618024.

- Tkinter.Canvas.scan_dragto() provides an optional parameter to support

the gain value which is passed to Tk. SF bug# 602259.

- Fix logging.handlers.SysLogHandler protocol when using UNIX domain sockets.

See SF patch #642974.

Tools/Demos

-----------

- Two new scripts (db2pickle.py and pickle2db.py) were added to the

Tools/scripts directory to facilitate conversion from the old bsddb module

to the new one. While the user-visible API of the new module is

compatible with the old one, it's likely that the version of the

underlying database library has changed. To convert from the old library,

run the db2pickle.py script using the old version of Python to convert it

to a pickle file. After upgrading Python, run the pickle2db.py script

using the new version of Python to reconstitute your database. For

example:

% python2.2 db2pickle.py -h some.db > some.pickle

% python2.3 pickle2db.py -h some.db.new < some.pickle

Run the scripts without any args to get a usage message.

Build

-----

- On systems which build using the configure script, compiler flags which

used to be lumped together using the OPT flag have been split into two

groups, OPT and BASECFLAGS. OPT is meant to carry just optimization- and

debug-related flags like "-g" and "-O3". BASECFLAGS is meant to carry

compiler flags that are required to get a clean compile. On some

platforms (many Linux flavors in particular) BASECFLAGS will be empty by

default. On others, such as Mac OS X and SCO, it will contain required

flags. This change allows people building Python to override OPT without

fear of clobbering compiler flags which are required to get a clean build.

- On Darwin/Mac OS X platforms, /sw/lib and /sw/include are added to the

relevant search lists in setup.py. This allows users building Python to

take advantage of the many packages available from the fink project

<http://fink.sf.net/>.

- A new Makefile target, scriptsinstall, installs a number of useful scripts

from the Tools/scripts directory.

C API

-----

- The PyArg_Parse functions now raise a TypeError instead of truncating float

arguments if an integer is specified (this affects the 'b', 'B', 'h', 'H',

'i', and 'l' codes).

New platforms

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

TBD

Tests

-----

TBD

Windows

-------

- distutils' msvccompiler class now passes the preprocessor options to

the resource compiler. See SF patch #669198.

- The bsddb module now ships with Sleepycat's 4.1.25.NC, the latest

release without strong cryptography.

- sys.path[0], if it contains a directory name, is now always an

absolute pathname.

- The new logging package is now installed by the Windows installer. It

wasn't in 2.3a1 due to oversight.

Mac

---

- There are new dialogs EasyDialogs.AskFileForOpen, AskFileForSave

and AskFolder. The old macfs.StandardGetFile and friends are deprecated.

- Type Carbon.File.FSCatalogInfo and supporting methods have been implemented.

This also makes macfs.FSSpec.SetDates() work again.

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).

- Fix problem with dynamic loading on 64-bit AIX (see bug #639945).

Extension modules

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

- Added three operators to the operator module:

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

operator.is_(a,b) which is equivalent to: a is b.

operator.is_not(a,b) which is equivalent to: a is not b.

- 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. For help converting your databases from the old module (which

probably used an obsolete version of Berkeley DB) to the new module, see

the db2pickle.py and pickle2db.py scripts described in the Tools/Demos

section above.

- 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.

- The linuxaudiodev module is now deprecated; it is being replaced by

ossaudiodev. The interface has been extended to cover a lot more of

OSS (see www.opensound.com), including most DSP ioctls and the

OSS mixer API. Documentation forthcoming in 2.3a2.

Library

-------

- imaplib.py now supports SSL (Tino Lange and Piers Lauder).

- 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 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