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+++++++++++
Python News
+++++++++++
(editors: check NEWS.help for information about editing NEWS using ReST.)
What's New in Python 3.1 alpha 0
================================
*Release date: XX-XXX-200X*
Core and Builtins
-----------------
- Issue #5186: Reduce hash collisions for objects with no __hash__ method by
rotating the object pointer by 4 bits to the right.
- Issue #4575: Fix Py_IS_INFINITY macro to work correctly on x87 FPUs:
it now forces its argument to double before testing for infinity.
- Issue #5137: Make len() correctly raise a TypeError when a __len__ method
returns a non-number type.
- Issue #5182: Removed memoryview.__str__.
- Issue #1717: Removed builtin cmp() function, dropped tp_compare
slot, the C API functions PyObject_Compare and PyUnicode_Compare and
the type definition cmpfunc. The tp_compare slot has been renamed
to tp_reserved, and is reserved for future usage.
- Issue 1242657: the __len__() and __length_hint__() calls in several tools
were suppressing all exceptions. These include list() and bytearray().
- Issue #4707: round(x, n) now returns an integer if x is an integer.
Previously it returned a float.
- Issue #4753: By enabling a configure option named '--with-computed-gotos'
on compilers that support it (notably: gcc, SunPro, icc), the bytecode
evaluation loop is compiled with a new dispatch mechanism which gives
speedups of up to 20%, depending on the system, on various benchmarks.
- Issue #4874: Most builtin decoders now reject unicode input.
- Issue #4842: Don't allow trailing 'L' when constructing an integer
from a string.
- Issue #4991: os.fdopen now raises an OSError for invalid file descriptors.
- Issue #4838: When a module is deallocated, free the memory backing the
optional module state data.
- Issue #4910: Rename nb_long slot to nb_reserved, and change its
type to (void *).
- Issue #4935: The overflow checking code in the expandtabs() method common
to str, bytes and bytearray could be optimized away by the compiler, letting
the interpreter segfault instead of raising an error.
- Issue #3720: Fix a crash when an iterator modifies its class and removes its
__next__ method.
- Issue #4910: Builtin int() function and PyNumber_Long/PyNumber_Int API
function no longer attempt to call the __long__ slot to convert an object
to an integer. Only the __int__ and __trunc__ slots are examined.
- Issue #4893: Use NT threading on CE.
- Issue #4915: Port sysmodule to Windows CE.
- Issue #4868: utf-8, utf-16 and latin1 decoding are now 2x to 4x faster. The
common cases are optimized thanks to a dedicated fast path and a moderate
amount of loop unrolling.
- Issue #4074: Change the criteria for doing a full garbage collection (i.e.
collecting the oldest generation) so that allocating lots of objects without
destroying them does not show quadratic performance. Based on a proposal by
Martin von Löwis at
http://mail.python.org/pipermail/python-dev/2008-June/080579.html.
- Issue #4604: Some objects of the I/O library could still be used after
having been closed (for instance, a read() call could return some
previously buffered data). Patch by Dmitry Vasiliev.
- Issue #4705: Fix the -u ("unbuffered binary stdout and stderr") command-line
flag to work properly. Furthermore, when specifying -u, the text stdout
and stderr streams have line-by-line buffering enabled (the default being
to buffer arbitrary chunks of data).
- The internal table, _PyLong_DigitValue, is now an array of unsigned chars
instead of ints (reducing its size from 4 to 8 times thereby reducing
Python's overall memory).
- Issue #1180193: When importing a module from a .pyc (or .pyo) file with
an existing .py counterpart, override the co_filename attributes of all
code objects if the original filename is obsolete (which can happen if the
file has been renamed, moved, or if it is accessed through different paths).
Patch by Ziga Seilnacht and Jean-Paul Calderone.
- Issue #4580: Fix slicing of memoryviews when the item size is greater than
one byte. Also fixes the meaning of len() so that it returns the number of
items, rather than the size in bytes.
- Issue #4075: Use OutputDebugStringW in Py_FatalError.
- Issue #4747: When the terminal does not use utf-8, executing a script with
non-ascii characters in its name could fail with a "SyntaxError: None" error.
- Issue #4797: IOError.filename was not set when _fileio.FileIO failed to open
file with `bytes' filename on Windows.
- Issue #3680: Reference cycles created through a dict, set or deque iterator
did not get collected.
- Issue #4701: PyObject_Hash now implicitly calls PyType_Ready on types
where the tp_hash and tp_dict slots are both NULL.
- Issue #4759: None is now allowed as the first argument of
bytearray.translate(). It was always allowed for bytes.translate().
- Added test case to ensure attempts to read from a file opened for writing
fail.
- Issue #3106: Speedup some comparisons (str/str and int/int).
- Issue #2183: Simplify and optimize bytecode for list, dict and set
comprehensions. Original patch for list comprehensions by Neal Norwitz.
- Issue #2467: gc.DEBUG_STATS reported invalid elapsed times. Also, always
print elapsed times, not only when some objects are uncollectable /
unreachable. Original patch by Neil Schemenauer.
- Issue #3439: Add a bit_length method to int.
- Issue #2173: When getting device encoding, check that return value of
nl_langinfo is not the empty string. This was causing silent build
failures on OS X.
- Issue #4597: Fixed several opcodes that weren't always propagating
exceptions.
- Issue #4589: Fixed exception handling when the __exit__ function of a
context manager returns a value that cannot be converted to a bool.
- Issue #4445: Replace "sizeof(PyBytesObject)" with
"offsetof(PyBytesObject, ob_sval) + 1" when allocating memory for
bytes instances. On a typical machine this saves 3 bytes of memory
(on average) per allocation of a bytes instance.
- Issue #4533: File read operation was dreadfully slow due to a slowly
growing read buffer. Fixed by using the same growth rate algorithm as
Python 2.x.
- Issue #4509: Various issues surrounding resize of bytearray objects to
which there are buffer exports (e.g. memoryview instances).
- Issue #4233: Changed semantic of ``_fileio.FileIO``'s ``close()``
method on file objects with closefd=False. The file descriptor is still
kept open but the file object behaves like a closed file. The ``FileIO``
object also got a new readonly attribute ``closefd``.
- Issue #4569: Interpreter crash when mutating a memoryview with an item size
larger than 1.
- Issue #4748: Lambda generators no longer return a value.
Library
-------
- Issue #5257: refactored all tests in distutils, so they use
support.TempdirManager, to avoid writing in the tests directory.
- Issue #4524: distutils build_script command failed with --with-suffix=3.
Initial patch by Amaury Forgeot d'Arc.
- Issue #2461: added tests for distutils.util
- Issue #4998: The memory saving effect of __slots__ had been lost on Fractions
which inherited from numbers.py which did not have __slots__ defined. The
numbers hierarchy now has its own __slots__ declarations.
- Issue #4631: Fix urlopen() result when an HTTP response uses chunked
encoding.
- Issue #5203: Fixed ctypes segfaults when passing a unicode string to a
function without argtypes (only occurs if HAVE_USABLE_WCHAR_T is false).
- Issue #3386: distutils.sysconfig.get_python_lib prefix argument was ignored
under NT and OS2. Patch by Philip Jenvey.
- Issue #5128: Make compileall properly inspect bytecode to determine if needs
to be recreated. This avoids a timing hole thanks to the old reliance on the
ctime of the files involved.
- Issue #5122: Synchronize tk load failure check to prevent a potential
deadlock.
- Issue #1818: collections.namedtuple() now supports a keyword argument
'rename' which lets invalid fieldnames be automatically converted to
positional names in the form, _1, _2, ...
- Issue #4890: Handle empty text search pattern in Tkinter.Text.search.
- Issue #4512 (part 2): Promote ``ZipImporter._get_filename()`` to be a
public documented method ``ZipImporter.get_filename()``.
- Issue #4195: The ``runpy`` module (and the ``-m`` switch) now support
the execution of packages by looking for and executing a ``__main__``
submodule when a package name is supplied. Initial patch by Andi
Vajda.
- Issue #1731706: Call Tcl_ConditionFinalize for Tcl_Conditions that will
not be used again (this requires Tcl/Tk 8.3.1), also fix a memory leak in
Tkapp_Call when calling from a thread different than the one that created
the Tcl interpreter. Patch by Robert Hancock.
- Issue #4285: Change sys.version_info to be a named tuple. Patch by
Ross Light.
- Issue #1520877: Now distutils.sysconfig reads $AR from the
environment/Makefile. Patch by Douglas Greiman.
- Issue #1276768: The verbose option was not used in the code of
distutils.file_util and distutils.dir_util.
- Issue #5132: Fixed trouble building extensions under Solaris with
--enabled-shared activated. Initial patch by Dave Peterson.
- Issue #1581476: Always use the Tcl global namespace when calling into Tcl.
- The shelve module now defaults to pickle protocol 3.
- Fix a bug in the trace module where a bytes object from co_lnotab had its
items being passed through ord().
- Issue #2047: shutil.move() could believe that its destination path was
inside its source path if it began with the same letters (e.g. "src" vs.
"src.new").
- Added the ttk module. See issue #2983: Ttk support for Tkinter.
- Removed isSequenceType(), isMappingType, and isNumberType() from the
operator module; use the abstract base classes instead. Also removed
the repeat() function; use mul() instead.
- Issue 5021: doctest.testfile() did not create __name__ and
collections.namedtuple() relied on __name__ being defined.
- Backport importlib from Python 3.1. Only the import_module() function has
been backported to help facilitate transitions from 2.7 to 3.1.
- Issue #1885: distutils. When running sdist with --formats=tar,gztar
the tar file was overriden by the gztar one.
- Issue #4863: distutils.mwerkscompiler has been removed.
- Added a new itertools functions: combinations_with_replacement()
and compress().
- Issue 5032: added a step argument to itertools.count() and
allowed non-integer arguments.
- Fix and properly document the multiprocessing module's logging
support, expose the internal levels and provide proper usage
examples.
- Issue #1672332: fix unpickling of subnormal floats, which was
producing a ValueError on some platforms.
- Issue #3881: Help Tcl to load even when started through the
unreadable local symlink to "Program Files" on Vista.
- Issue #4710: Extract directories properly in the zipfile module;
allow adding directories to a zipfile.
- Issue #3807: _multiprocessing build fails when configure is passed
--without-threads argument. When this occurs, _multiprocessing will
be disabled, and not compiled.
- Issue #5008: When a file is opened in append mode with the new IO library,
do an explicit seek to the end of file (so that e.g. tell() returns the
file size rather than 0). This is consistent with the behaviour of the
traditional 2.x file object.
- Issue #5013: Fixed a bug in FileHandler which occurred when the delay
parameter was set.
- Issue #4842: Always append a trailing 'L' when pickling longs using
pickle protocol 0. When reading, the 'L' is optional.
- Add the importlib package.
- Issue #4301: Patch the logging module to add processName support, remove
_check_logger_class from multiprocessing.
- Issue #3325: Remove python2.x try: except: imports for old cPickle from
multiprocessing.
- Issue #4959: inspect.formatargspec now works for keyword only arguments
without defaults.
- Issue #3321: _multiprocessing.Connection() doesn't check handle; added checks
for *nix machines for negative handles and large int handles. Without this check
it is possible to segfault the interpreter.
- Issue #4449: AssertionError in mp_benchmarks.py, caused by an underlying issue
in sharedctypes.py.
- Issue #1225107: inspect.isclass() returned True for instances with a custom
__getattr__.
- Issue #3826 and #4791: The socket module now closes the underlying socket
appropriately when it is being used via socket.makefile() objects
rather than delaying the close by waiting for garbage collection to do it.
- Issue #1696199: Add collections.Counter() for rapid and convenient
counting.
- Issue #3860: GzipFile and BZ2File now support the context manager protocol.
- Issue #4867: Fixed a crash in ctypes when passing a string to a
function without defining argtypes.
- Issue #4272: Add an optional argument to the GzipFile constructor to override
the timestamp in the gzip stream. The default value remains the current time.
The information can be used by e.g. gunzip when decompressing. Patch by
Jacques Frechet.
- Restore Python 2.3 compatibility for decimal.py.
- Issue #3638: Remove functions from _tkinter module level that depend on
TkappObject to work with multiple threads.
- Issue #4718: Adapt the wsgiref package so that it actually works with
Python 3.x, in accordance with the `official amendments of the spec
<http://www.wsgi.org/wsgi/Amendments_1.0>`_.
- Issue #4796: Added Decimal.from_float() and Context.create_decimal_from_float()
to the decimal module.
- Fractions.from_float() no longer loses precision for integers too big to
cast as floats.
- Issue #4812: add missing underscore prefix to some internal-use-only
constants in the decimal module. (Dec_0 becomes _Dec_0, etc.)
- Issue 4790: The nsmallest() and nlargest() functions in the heapq module
did unnecessary work in the common case where no key function was specified.
- Issue #4795: inspect.isgeneratorfunction() returns False instead of None when
the function is not a generator.
- Issue #4702: Throwing a DistutilsPlatformError instead of IOError in case
no MSVC compiler is found under Windows. Original patch by Philip Jenvey.
- Issue #4646: distutils was choking on empty options arg in the setup
function. Original patch by Thomas Heller.
- Issue #3767: Convert Tk object to string in tkColorChooser.
- Issue #3248: Allow placing ScrolledText in a PanedWindow.
- Issue #4444: Allow assertRaises() to be used as a context handler, so that
the code under test can be written inline if more practical.
- Issue #4739: Add pydoc help topics for symbols, so that e.g. help('@')
works as expected in the interactive environment.
- Issue #4756: zipfile.is_zipfile() now supports file-like objects. Patch by
Gabriel Genellina.
- Issue #4574: reading an UTF16-encoded text file crashes if \r on 64-char
boundary.
- Issue #4223: inspect.getsource() will now correctly display source code
for packages loaded via zipimport (or any other conformant PEP 302
loader). Original patch by Alexander Belopolsky.
- Issue #4201: pdb can now access and display source code loaded via
zipimport (or any other conformant PEP 302 loader). Original patch by
Alexander Belopolsky.
- Issue #4197: doctests in modules loaded via zipimport (or any other PEP
302 conformant loader) will now work correctly in most cases (they
are still subject to the constraints that exist for all code running
from inside a module loaded via a PEP 302 loader and attempting to
perform IO operations based on __file__). Original patch by
Alexander Belopolsky.
- Issues #4082 and #4512: Add runpy support to zipimport in a manner that
allows backporting to maintenance branches. Original patch by
Alexander Belopolsky.
- Issue #4163: textwrap module: allow word splitting on a hyphen preceded by
a non-ASCII letter.
- Issue #4616: TarFile.utime(): Restore directory times on Windows.
- Issue #4021: tokenize.detect_encoding() now raises a SyntaxError when the
codec cannot be found. This is for compatibility with the builtin behavior.
- Issue #4084: Fix max, min, max_mag and min_mag Decimal methods to
give correct results in the case where one argument is a quiet NaN
and the other is a finite number that requires rounding.
- Issue #4483: _dbm module now builds on systems with gdbm & gdbm_compat
libs.
- Added the subprocess.check_call_output() convenience function to get output
from a subprocess on success or raise an exception on error.
- Issue #1055234: cgi.parse_header(): Fixed parsing of header parameters to
support unusual filenames (such as those containing semi-colons) in
Content-Disposition headers.
- Issue #4384: Added logging integration with warnings module using
captureWarnings(). This change includes a NullHandler which does nothing;
it will be of use to library developers who want to avoid the "No handlers
could be found for logger XXX" message which can appear if the library user
doesn't configure logging.
- Issue #3741: DISTUTILS_USE_SDK set causes msvc9compiler.py to raise an
exception.
- Issue #4529: fix the parser module's validation of try-except-finally
statements.
- Issue #4458: getopt.gnu_getopt() now recognizes a single "-" as an argument,
not a malformed option.
- Added the subprocess.check_output() convenience function to get output
from a subprocess on success or raise an exception on error.
- Issue #4542: On Windows, binascii.crc32 still accepted str as binary input;
the corresponding tests now pass.
- Issue #4537: webbrowser.UnixBrowser would fail to open the browser because
it was calling the wrong open() function.
- Issue #1055234: cgi.parse_header(): Fixed parsing of header parameters to
support unusual filenames (such as those containing semi-colons) in
Content-Disposition headers.
- Issue #4861: ctypes.util.find_library(): Robustify. Fix library detection on
biarch systems. Try to rely on ldconfig only, without using objdump and gcc.
- Issue #5104: The socket module now raises OverflowError when 16-bit port and
protocol numbers are supplied outside the allowed 0-65536 range on bind()
and getservbyport().
Tools/Demos
-----------
- Issue #4704: remove use of cmp() in pybench, bump its version number to 2.1,
and make it 2.6-compatible.
- Ttk demos added in Demo/tkinter/ttk/
- Issue #4677: add two list comprehension tests to pybench.
Build
-----
- Issue #5134: Silence compiler warnings when compiling sqlite with VC++.
- Issue #4494: Fix build with Py_NO_ENABLE_SHARED on Windows.
- Issue #4895: Use _strdup on Windows CE.
- Issue #4472: "configure --enable-shared" now works on OSX
- Issues #4728 and #4060: WORDS_BIGEDIAN is now correct in Universal builds.
- Issue #4389: Add icon to the uninstall entry in "add-and-remove-programs".
- Issue #4289: Remove Cancel button from AdvancedDlg.
- Issue #1656675: Register a drop handler for .py* files on Windows.
- Issue #4120: Exclude manifest from extension modules in VS2008.
- Issue #4091: Install pythonxy.dll in system32 again.
- Issue #4018: Disable "for me" installations on Vista.
- Issue #3758: Add ``patchcheck`` build target to .PHONY.
- Issue #4204: Fixed module build errors on FreeBSD 4.
C-API
-----
- Issue #5175: PyLong_AsUnsignedLongLong now raises OverflowError
for negative arguments. Previously, it raised TypeError.
- Issue #4720: The format for PyArg_ParseTupleAndKeywords can begin with '|'.
- Issue #3632: from the gdb debugger, the 'pyo' macro can now be called when
the GIL is released, or owned by another thread.
- Issue #4122: On Windows, fix a compilation error when using the
Py_UNICODE_ISSPACE macro in an extension module.
Extension Modules
-----------------
- Issue #3745: Fix hashlib to always reject unicode and non buffer-api
supporting objects as input no matter how it was compiled (built in
implementations or external openssl library).
- Issue #4397: Fix occasional test_socket failure on OS X.
- Issue #4279: Fix build of parsermodule under Cygwin.
- Issue #4751: hashlib now releases the GIL when hashing large buffers
(with a hardwired threshold of 2048 bytes), allowing better parallelization
on multi-CPU systems. Contributed by Lukas Lueg (ebfe) and Victor Stinner.
- Issue #4051: Prevent conflict of UNICODE macros in cPickle.
- Issue #4738: Each zlib object now has a separate lock, allowing to compress
or decompress several streams at once on multi-CPU systems. Also, the GIL
is now released when computing the CRC of a large buffer. Patch by ebfe.
- Issue #4228: Pack negative values the same way as 2.4 in struct's L format.
- Issue #1040026: Fix os.times result on systems where HZ is incorrect.
- Issues #3167, #3682: Fix test_math failures for log, log10 on Solaris,
OpenBSD.
- Issue #4583: array.array would not always prohibit resizing when a buffer
has been exported, resulting in an interpreter crash when accessing the
buffer.
Tests
-----
- Issue #5083: New 'gui' resource for regrtest.
Docs
----
**(For information about older versions, consult the HISTORY file.)**
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