Optimizations
-------------
-A few performance enhancements have been added:
+Several performance enhancements have been added:
+
+.. * A new :program:`configure` option, :option:`--with-computed-gotos`,
+ compiles the main bytecode interpreter loop using a new dispatch
+ mechanism that gives speedups of up to 20%, depending on the system
+ and benchmark. The new mechanism is only supported on certain
+ compilers, such as gcc, SunPro, and icc.
* The garbage collector now performs better when many objects are
being allocated without deallocating any. A full garbage collection
(Contributed by Mark Dickinson; :issue:`4258`.)
Another set of changes made long objects a few bytes smaller: 2 bytes
- smaller on 32-bit systems and 6 bytes on 64-bit. (:
+ smaller on 32-bit systems and 6 bytes on 64-bit.
(Contributed by Mark Dickinson; :issue:`5260`.)
* The division algorithm for long integers has been made faster
integer divisions and modulo operations.
(Contributed by Mark Dickinson; :issue:`5512`.)
+* List comprehensions with an ``if`` condition are compiled into
+ faster bytecode. (Patch by Antoine Pitrou, back-ported to 2.7
+ by Jeffrey Yasskin; :issue:`4715`.)
+
.. ======================================================================
New, Improved, and Deprecated Modules
:file:`Misc/NEWS` file in the source tree for a more complete list of
changes, or look through the Subversion logs for all the details.
-* It is no longer mandatory to store clear-text passwords in the
- :file:`.pypirc` file when registering and uploading packages to PyPI. As long
- as the username is present in that file, the :mod:`distutils` package will
- prompt for the password if not present. (Added by Tarek Ziade,
- with the initial contribution by Nathan Van Gheem; :issue:`4394`.)
-
* The :mod:`bz2` module's :class:`BZ2File` now supports the context
management protocol, so you can write ``with bz2.BZ2File(...) as f: ...``.
(Contributed by Hagen Fuerstenau; :issue:`3860`.)
Contributed by Raymond Hettinger; :issue:`1696199`.
* In Distutils, :func:`distutils.sdist.add_defaults` now uses
- *package_dir* and *data_files* to feed MANIFEST.
+ *package_dir* and *data_files* to create the MANIFEST file.
+
+ It is no longer mandatory to store clear-text passwords in the
+ :file:`.pypirc` file when registering and uploading packages to PyPI. As long
+ as the username is present in that file, the :mod:`distutils` package will
+ prompt for the password if not present. (Added by Tarek Ziade,
+ with the initial contribution by Nathan Van Gheem; :issue:`4394`.)
+
+* New method: the :class:`Decimal` class gained a
+ :meth:`from_float` class method that performs an exact conversion
+ of a floating-point number to a :class:`Decimal`.
+ Note that this is an **exact** conversion that strives for the
+ closest decimal approximation to the floating-point representation's value;
+ the resulting decimal value will therefore still include the inaccuracy,
+ if any.
+ For example, ``Decimal.from_float(0.1)`` returns
+ ``Decimal('0.1000000000000000055511151231257827021181583404541015625')``.
+ (Implemented by Raymond Hettinger; :issue:`4796`.)
* A new function in the :mod:`gc` module, :func:`is_tracked`, returns
True if a given instance is tracked by the garbage collector, False
* The :mod:`gzip` module's :class:`GzipFile` now supports the context
management protocol, so you can write ``with gzip.GzipFile(...) as f: ...``.
(Contributed by Hagen Fuerstenau; :issue:`3860`.)
+ It's now possible to override the modification time
+ recorded in a gzipped file by providing an optional timestamp to
+ the constructor. (Contributed by Jacques Frechet; :issue:`4272`.)
* The :class:`io.FileIO` class now raises an :exc:`OSError` when passed
an invalid file descriptor. (Implemented by Benjamin Peterson;
floats or :class:`Decimal` instances. (Implemented by Raymond
Hettinger; :issue:`5032`.)
+ :func:`itertools.combinations` and :func:`itertools.product` were
+ previously raising :exc:`ValueError` for values of *r* larger than
+ the input iterable. This was deemed a specification error, so they
+ now return an empty iterator. (Fixed by Raymond Hettinger; :issue:`4816`.)
+
* The :mod:`json` module was upgraded to version 2.0.9 of the
simplejson package, which includes a C extension that makes
encoding and decoding faster.
is particularly useful for asynchronous IO operations.
(Contributed by Kristjan Valur Jonsson; :issue:`4293`.)
+* The :program:`configure` script now checks for floating-point rounding bugs
+ on certain 32-bit Intel chips and defines a :cmacro:`X87_DOUBLE_ROUNDING`
+ preprocessor definition. No code currently uses this definition,
+ but it's available if anyone wishes to use it.
+ (Added by Mark Dickinson; :issue:`2937`.)
.. ======================================================================
Port-Specific Changes: Mac OS X
-----------------------------------
+* The ``/Library/Python/2.7/site-packages`` is now appended to
+ ``sys.path``, in order to share added packages between the system
+ installation and a user-installed copy of the same version.
+ (Changed by Ronald Oussoren; :issue:`4865`.)
+
Other Changes and Fixes
=======================
+* When importing a module from a :file:`.pyc` or :file:`.pyo` file
+ with an existing :file:`.py` counterpart, the :attr:`co_filename`
+ attributes of all code objects if the original filename is obsolete,
+ which can happen if the file has been renamed, moved, or is accessed
+ through different paths. (Patch by Ziga Seilnacht and Jean-Paul
+ Calderone; :issue:`1180193`.)
+
* The :file:`regrtest.py` script now takes a :option:`--randseed=`
switch that takes an integer that will be used as the random seed
for the :option:`-r` option that executes tests in random order.
projects / thirdparty / Python / cpython.git / commitdiff
