| **************************** |
| What's New In Python 3.2 |
| **************************** |
| |
| :Author: Raymond Hettinger |
| :Release: |release| |
| :Date: |today| |
| |
| .. $Id$ |
| Rules for maintenance: |
| |
| * Anyone can add text to this document. Do not spend very much time |
| on the wording of your changes, because your text will probably |
| get rewritten. |
| |
| * The maintainer will go through Misc/NEWS periodically and add |
| changes; it's therefore more important to add your changes to |
| Misc/NEWS than to this file. |
| |
| * This is not a complete list of every single change; completeness |
| is the purpose of Misc/NEWS. Some changes I consider too small |
| or esoteric to include. If such a change is added to the text, |
| I'll just remove it. (This is another reason you shouldn't spend |
| too much time on writing your addition.) |
| |
| * If you want to draw your new text to the attention of the |
| maintainer, add 'XXX' to the beginning of the paragraph or |
| section. |
| |
| * It's OK to just add a fragmentary note about a change. For |
| example: "XXX Describe the transmogrify() function added to the |
| socket module." The maintainer will research the change and |
| write the necessary text. |
| |
| * You can comment out your additions if you like, but it's not |
| necessary (especially when a final release is some months away). |
| |
| * Credit the author of a patch or bugfix. Just the name is |
| sufficient; the e-mail address isn't necessary. It's helpful to |
| add the issue number: |
| |
| XXX Describe the transmogrify() function added to the socket |
| module. |
| |
| (Contributed by P.Y. Developer; :issue:`12345`.) |
| |
| This saves the maintainer the effort of going through the SVN log |
| when researching a change. |
| |
| This article explains the new features in Python 3.2, compared to 3.1. |
| It focuses on a few highlights and gives a few examples. For full details, |
| see the :file:`Misc/NEWS` file. |
| |
| |
| PEP 384: Defining a Stable ABI |
| ============================== |
| |
| In the past, extension modules built for one Python version were often |
| not usable with other Python versions. Particularly on Windows, every |
| feature release of Python required rebuilding all extension modules that |
| one wanted to use. This requirement was the result of the free access to |
| Python interpreter internals that extension modules could use. |
| |
| With Python 3.2, an alternative approach becomes available: extension |
| modules which restrict themselves to a limited API (by defining |
| Py_LIMITED_API) cannot use many of the internals, but are constrained |
| to a set of API functions that are promised to be stable for several |
| releases. As a consequence, extension modules built for 3.2 in that |
| mode will also work with 3.3, 3.4, and so on. Extension modules that |
| make use of details of memory structures can still be built, but will |
| need to be recompiled for every feature release. |
| |
| .. seealso:: |
| |
| :pep:`384` - Defining a Stable ABI |
| PEP written by Martin von Löwis. |
| |
| PEP 389: Argparse Command Line Parsing Module |
| ============================================= |
| |
| A new module for command line parsing, :mod:`argparse`, was introduced to |
| overcome the limitations of :mod:`optparse` which did not provide support for |
| positional arguments (not just options), subcommands, required options and other |
| common patterns of specifying and validating options. |
| |
| This module has already has wide-spread success in the community as a |
| third-party module. Being more fully featured than its predecessor, the |
| :mod:`argparse` module is now the preferred module for command-line processing. |
| The older module is still being kept available because of the substantial amount |
| of legacy code that depends on it. |
| |
| Here's an annotated example parser showing features like limiting results to a |
| set of choices, specifying a *metavar* in the help screen, validating that one |
| or more positional arguments is present, and making a required option:: |
| |
| import argparse |
| parser = argparse.ArgumentParser( |
| description = 'Manage servers', # main description for help |
| epilog = 'Tested on Solaris and Linux') # displayed after help |
| parser.add_argument('action', # argument name |
| choices = ['deploy', 'start', 'stop'], # one of four allowed values |
| help = 'action on each target') # help msg |
| parser.add_argument('targets', |
| metavar = 'HOSTNAME', # var name used in help msg |
| nargs = '+', # require 1 or more targets |
| help = 'url for target machines') # help msg explanation |
| parser.add_argument('-u', '--user', # -u or --user option |
| required = True, # make this a required argument |
| help = 'login as user') |
| |
| Example of calling the parser on a command string:: |
| |
| >>> cmd = 'deploy sneezy.example.com sleepy.example.com -u skycaptain' |
| >>> result = parser.parse_args(cmd.split()) |
| |
| >>> # parsed variables are stored in the attributes |
| >>> result.action |
| 'deploy' |
| >>> result.targets |
| ['sneezy.example.com', 'sleepy.example.com'] |
| >>> result.user |
| 'skycaptain' |
| |
| Example of the parser's automatically generated help:: |
| |
| >>> parser.parse_args('-h'.split()) |
| |
| usage: manage_cloud.py [-h] -u USER |
| {deploy,start,stop} HOSTNAME [HOSTNAME ...] |
| |
| Manage servers |
| |
| positional arguments: |
| {deploy,start,stop} action on each target |
| HOSTNAME url for target machines |
| |
| optional arguments: |
| -h, --help show this help message and exit |
| -u USER, --user USER login as user |
| |
| Tested on Solaris and Linux |
| |
| An especially nice :mod:`argparse` feature is the ability to define subparsers, |
| each with their own argument patterns and help displays:: |
| |
| import argparse |
| parser = argparse.ArgumentParser(prog='HELM') |
| subparsers = parser.add_subparsers() |
| |
| parser_l = subparsers.add_parser('launch', help='Launch Control') # first subgroup |
| parser_l.add_argument('-m', '--missles', action='store_true') |
| parser_l.add_argument('-t', '--torpedos', action='store_true') |
| |
| parser_m = subparsers.add_parser('move', help='Move Vessel') # second subgroup |
| parser_m.add_argument('-c', '--course', type=int, required=True) |
| parser_m.add_argument('-s', '--speed', type=int, default=0) |
| |
| $ ./helm.py --help # top level help (launch and move) |
| $ ./helm.py launch --help # help for launch options |
| $ ./helm.py launch --missiles # set missiles=True and torpedos=False |
| $ ./helm.py move --course 180 --speed 5 # set movement parameters |
| |
| .. seealso:: |
| |
| :pep:`389` - New Command Line Parsing Module |
| PEP written by Steven Bethard. |
| |
| :ref:`upgrading-optparse-code` for details on the differences from |
| :mod:`optparse`. |
| |
| |
| PEP 391: Dictionary Based Configuration for Logging |
| ==================================================== |
| |
| The :mod:`logging` module provided two kinds of configuration, one style with |
| function calls for each option or another style driven by an external file saved |
| in a :mod:`ConfigParser` format. Those options did not provide the flexibility |
| to create configurations from JSON or YAML files, nor did they support |
| incremental configuration, which is needed for specifying logger options from a |
| command line. |
| |
| To support a more flexible style, the module now offers |
| :func:`logging.config.dictConfig` for specifying logging configuration with |
| plain Python dictionaries. The configuration options include formatters, |
| handlers, filters, and loggers. Here's a working example of a configuration |
| dictionary:: |
| |
| {"version": 1, |
| "formatters": {"brief": {"format": "%(levelname)-8s: %(name)-15s: %(message)s"}, |
| "full": {"format": "%(asctime)s %(name)-15s %(levelname)-8s %(message)s"}, |
| }, |
| "handlers": {"console": { |
| "class": "logging.StreamHandler", |
| "formatter": "brief", |
| "level": "INFO", |
| "stream": "ext://sys.stdout"}, |
| "console_priority": { |
| "class": "logging.StreamHandler", |
| "formatter": "full", |
| "level": "ERROR", |
| "stream": "ext://sys.stderr"}, |
| }, |
| "root": {"level": "DEBUG", "handlers": ["console", "console_priority"]}} |
| |
| |
| If that dictionary is stored in a file called :file:`conf.json`, it can loaded |
| and called with code like this:: |
| |
| >>> import logging.config |
| >>> logging.config.dictConfig(json.load(open('conf.json', 'rb'))) |
| >>> logging.info("Transaction completed normally") |
| >>> logging.critical("Abnormal termination") |
| |
| .. seealso:: |
| |
| :pep:`391` - Dictionary Based Configuration for Logging |
| PEP written by Vinay Sajip. |
| |
| PEP 3148: The ``concurrent.futures`` module |
| ============================================ |
| |
| Code for creating and managing concurrency is being collected in a new toplevel |
| namespace, *concurrent*. Its first member is a *futures* package which provides |
| a uniform high level interface for managing threads and processes. |
| |
| The design for :mod:`concurrent.futures` was inspired by |
| *java.util.concurrent.package*. In that model, a running call and its result |
| are represented by a :class:`~concurrent.futures.Future` object which abstracts |
| features common to threads, processes, and remote procedure calls. That object |
| supports status checks (running or done), timeouts, cancellations, adding |
| callbacks, and access to results or exceptions. |
| |
| The primary offering of the new module is a pair of executor classes for |
| launching and managing calls. The goal of the executors is to make it easier to |
| use existing tools for making parallel calls. They save the effort needed to |
| setup a pool of resources, launch the calls, create a results queue, add |
| time-out handling, and limit the total number of threads, processes, or remote |
| procedure calls. |
| |
| Ideally, each application should share a single executor across multiple |
| components so that process and thread limits can be centrally managed. This |
| solves the design challenge that arises when each component has its own |
| competing strategy for resource management. |
| |
| Both classes share a common interface with three methods: |
| :meth:`~concurrent.futures.Executor.submit` for scheduling a callable and |
| returning a :class:`~concurrent.futures.Future` object; |
| :meth:`~concurrent.futures.Executor.map` for scheduling many asynchronous calls |
| at a time, and :meth:`~concurrent.futures.Executor.shutdown` for freeing |
| resources. The class is a :term:`context manager` and can be used within a |
| :keyword:`with` statement to assure that resources are automatically released |
| when currently pending futures are done executing. |
| |
| A simple of example of :class:`~concurrent.futures.ThreadPoolExecutor` is a |
| launch of four parallel threads for copying files:: |
| |
| import shutil |
| with ThreadPoolExecutor(max_workers=4) as e: |
| e.submit(shutil.copy, 'src1.txt', 'dest1.txt') |
| e.submit(shutil.copy, 'src2.txt', 'dest2.txt') |
| e.submit(shutil.copy, 'src3.txt', 'dest3.txt') |
| e.submit(shutil.copy, 'src3.txt', 'dest4.txt') |
| |
| .. seealso:: |
| |
| :pep:`3148` - Futures -- Execute Computations Asynchronously |
| PEP written by Brain Quinlan. |
| |
| :ref:`Code for Threaded Parallel URL reads<threadpoolexecutor-example>`, an |
| example using threads to fetch multiple web pages in parallel. |
| |
| :ref:`Code for computing prime numbers in |
| parallel<processpoolexecutor-example>`, an example demonstrating |
| :class:`~concurrent.futures.ProcessPoolExecutor`. |
| |
| |
| |
| PEP 3147: PYC Repository Directories |
| ===================================== |
| |
| Python's scheme for caching bytecode in *.pyc* files did not work well in |
| environments with multiple python interpreters. If one interpreter encountered |
| a cached file created by another interpreter, it would recompile the source and |
| overwrite the cached file, thus losing the benefits of caching. |
| |
| The issue of "pyc fights" has become more pronounced as it has become |
| commonplace for Linux distributions to ship with multiple versions of Python. |
| These conflicts also arise with CPython alternatives such as Unladen Swallow. |
| |
| To solve this problem, Python's import machinery has been extended to use |
| distinct filenames for each interpreter. Instead of Python 3.2 and Python 3.3 and |
| Unladen Swallow each competing for a file called "mymodule.pyc", they will now |
| look for "mymodule.cpython-32.pyc", "mymodule.cpython-33.pyc", and |
| "mymodule.unladen10.pyc". And to prevent all of these new files from |
| cluttering source directories, the *pyc* files are now collected in a |
| "__pycache__" directory stored under the package directory. |
| |
| Aside from the filenames and target directories, the new scheme has a few |
| aspects that are visible to the programmer: |
| |
| * Imported modules now have a :attr:`__cached__` attribute which stores the name |
| of the actual file that was imported: |
| |
| >>> import collections |
| >>> collections.__cached__ |
| 'c:/py32/lib/__pycache__/collections.cpython-32.pyc' |
| |
| * The tag that is unique to each interpreter is accessible from the :mod:`imp` |
| module: |
| |
| >>> import imp |
| >>> imp.get_tag() |
| 'cpython-32' |
| |
| * Scripts that try to deduce source filename from the imported file now need to |
| be smarter. It is no longer sufficient to simply strip the "c" from a ".pyc" |
| filename. Instead, use the new functions in the :mod:`imp` module: |
| |
| >>> imp.source_from_cache('c:/py32/lib/__pycache__/collections.cpython-32.pyc') |
| 'c:/py32/lib/collections.py' |
| >>> imp.cache_from_source('c:/py32/lib/collections.py') |
| 'c:/py32/lib/__pycache__/collections.cpython-32.pyc' |
| |
| * The :mod:`py_compile` and :mod:`compileall` modules have been updated to |
| reflect the new naming convention and target directory. |
| |
| .. seealso:: |
| |
| :pep:`3147` - PYC Repository Directories |
| PEP written by Barry Warsaw. |
| |
| |
| PEP 3149: ABI Version Tagged .so Files |
| ====================================== |
| |
| The PYC repository directory allows multiple bytecode cache files to be |
| co-located. This PEP implements a similar mechanism for shared object files by |
| giving them a common directory and distinct names for each version. |
| |
| The common directory is "pyshared" and the file names are made distinct by |
| identifying the Python implementation (such as CPython, PyPy, Jython, etc.), the |
| major and minor version numbers, and optional build flags (such as "d" for |
| debug, "m" for pymalloc, "u" for wide-unicode). For an arbitrary package "foo", |
| you may see these files when the distribution package is installed:: |
| |
| /usr/share/pyshared/foo.cpython-32m.so |
| /usr/share/pyshared/foo.cpython-33md.so |
| |
| In Python itself, the tags are accessible from functions in the :mod:`sysconfig` |
| module:: |
| |
| >>> import sysconfig |
| >>> sysconfig.get_config_var('SOABI') # find the version tag |
| 'cpython-32mu' |
| >>> sysconfig.get_config_var('SO') # find the full filename extension |
| 'cpython-32mu.so' |
| |
| .. seealso:: |
| |
| :pep:`3149` - ABI Version Tagged .so Files |
| PEP written by Barry Warsaw. |
| |
| |
| Email |
| ===== |
| |
| The usability of the :mod:`email` package in Python 3 has been mostly fixed by |
| the extensive efforts of R. David Murray. The problem was that emails are |
| typically read and stored in the form of :class:`bytes` rather than :class:`str` |
| text, and they may contain multiple encodings within a single email. So, the |
| email package had to be extended to parse and generate email messages in bytes |
| format. |
| |
| * New functions :func:`~email.message_from_bytes` and |
| :func:`~email.message_from_binary_file`, and new classes |
| :class:`~email.parser.BytesFeedParser` and :class:`~email.parser.BytesParser` |
| allow binary message data to be parsed into model objects. |
| |
| * Given bytes input to the model, :meth:`~email.message.Message.get_payload` |
| will by default decode a message body that has a |
| :mailheader:`Content-Transfer-Encoding` of *8bit* using the charset |
| specified in the MIME headers and return the resulting string. |
| |
| * Given bytes input to the model, :class:`~email.generator.Generator` will |
| convert message bodies that have a :mailheader:`Content-Transfer-Encoding` of |
| *8bit* to instead have a *7bit* :mailheader:`Content-Transfer-Encoding`. |
| |
| * A new class :class:`~email.generator.BytesGenerator` produces bytes as output, |
| preserving any unchanged non-ASCII data that was present in the input used to |
| build the model, including message bodies with a |
| :mailheader:`Content-Transfer-Encoding` of *8bit*. |
| |
| * The :mod:`smtplib` :class:`~smtplib.SMTP` class now accepts a byte string |
| for the *msg* argument to the :meth:`~smtplib.SMTP.sendmail` method, |
| and a new method, :meth:`~smtplib.SMTP.send_message` accepts a |
| :class:`~email.message.Message` object and can optionally obtain the |
| *from_addr* and *to_addrs* addresses directly from the object. |
| |
| .. XXX Update before 3.2rc1 to reflect all of the last work and add examples. |
| |
| (Proposed and implemented by R. David Murray, :issue:`4661` and :issue:`10321`.) |
| |
| |
| Other Language Changes |
| ====================== |
| |
| Some smaller changes made to the core Python language are: |
| |
| * String formatting for :func:`format` and :meth:`str.format` gained new |
| capabilities for the format character **#**. Previously, for integers in |
| binary, octal, or hexadecimal, it caused the output to be prefixed with '0b', |
| '0o', or '0x' respectively. Now it can also handle floats, complex, and |
| Decimal, causing the output to always have a decimal point even when no digits |
| follow it. |
| |
| >>> format(20, '#o') |
| '0o24' |
| >>> format(12.34, '#5.0f') |
| ' 12.' |
| |
| (Suggested by Mark Dickinson and implemented by Eric Smith in :issue:`7094`.) |
| |
| * The interpreter can now be started with a quiet option, ``-q``, to suppress |
| the copyright and version information in an interactive mode. |
| |
| (Contributed by Marcin Wojdyr in issue:`1772833`). |
| |
| * The :func:`hasattr` function used to catch and suppress any Exception. Now, |
| it only catches :exc:`AttributeError`. Under the hood, :func:`hasattr` works |
| by calling :func:`getattr` and throwing away the results. This is necessary |
| because dynamic attribute creation is possible using :meth:`__getattribute__` |
| or :meth:`__getattr__`. If :func:`hasattr` were to just scan instance and class |
| dictionaries it would miss the dynamic methods and make it difficult to |
| implement proxy objects. |
| |
| To support lookups without the possibility of activating a dynamic attribute, |
| the :mod:`inspect` module has a new function, :func:`~inspect.getattr_static`. |
| |
| (Discovered by Yury Selivanov and fixed by Benjamin Peterson; :issue:`9666`. |
| The inspect function added by Michael Foord.) |
| |
| * The :func:`str` of a float or complex number is now the same as its |
| :func:`repr`. Previously, the :func:`str` form was shorter but that just |
| caused confusion and is no longer needed now that the shortest possible |
| :func:`repr` is displayed by default: |
| |
| >>> repr(math.pi) |
| '3.141592653589793' |
| >>> str(math.pi) |
| '3.141592653589793' |
| |
| (Proposed and implemented by Mark Dickinson; :issue:`9337`.) |
| |
| * :class:`memoryview` objects now have a :meth:`~memoryview.release()` method |
| and they also now support the context manager protocol. This allows timely |
| release of any resources that were acquired when requesting a buffer from the |
| original object. |
| |
| >>> with memoryview(b'abcdefgh') as v: |
| ... print(v.tolist()) |
| ... |
| [97, 98, 99, 100, 101, 102, 103, 104] |
| |
| (Added by Antoine Pitrou; :issue:`9757`.) |
| |
| * Mark Dickinson crafted an elegant and efficient scheme for assuring that |
| different numeric datatypes will have the same hash value whenever their |
| actual values are equal:: |
| |
| >>> assert hash(Fraction(3, 2)) == hash(1.5) == \ |
| hash(Decimal("1.5")) == hash(complex(1.5, 0)) |
| |
| (See :issue:`8188`.) |
| |
| * Previously it was illegal to delete a name from the local namespace if it |
| occurs as a free variable in a nested block:: |
| |
| >>> def outer(x): |
| ... def inner(): |
| ... return x |
| ... inner() |
| ... del x |
| |
| This is now allowed. Remember that the target of an :keyword:`except` clause |
| is cleared, so this code which used to work with Python 2.6, raised a |
| :exc:`SyntaxError` with Python 3.1 and now works again:: |
| |
| >>> def f(): |
| ... def print_error(): |
| ... print(e) |
| ... try: |
| ... something |
| ... except Exception as e: |
| ... print_error() |
| ... # implicit "del e" here |
| |
| (See :issue:`4617`.) |
| |
| * A new warning category, :exc:`ResourceWarning`, has been added. It is |
| emitted when potential issues with resource consumption or cleanup |
| are detected. It is silenced by default in normal release builds, but |
| can be enabled through the means provided by the :mod:`warnings` |
| module, or on the command line. |
| |
| A :exc:`ResourceWarning` is issued at interpreter shutdown if the |
| :data:`gc.garbage` list isn't empty. This is meant to make the programmer |
| aware that their code contains object finalization issues. |
| |
| A :exc:`ResourceWarning` is also issued when a :term:`file object` is destroyed |
| without having been explicitly closed. While the deallocator for such |
| object ensures it closes the underlying operating system resource |
| (usually, a file descriptor), the delay in deallocating the object could |
| produce various issues, especially under Windows. Here is an example |
| of enabling the warning from the command line:: |
| |
| $ ./python -q -Wdefault |
| >>> f = open("foo", "wb") |
| >>> del f |
| __main__:1: ResourceWarning: unclosed file <_io.BufferedWriter name='foo'> |
| |
| (Added by Antoine Pitrou and Georg Brandl in :issue:`10093` and :issue:`477863`.) |
| |
| * :class:`range` objects now support *index* and *count* methods. This is part |
| of an effort to make more objects fully implement the |
| :class:`collections.Sequence` :term:`abstract base class`. As a result, the |
| language will have a more uniform API. In addition, :class:`range` objects |
| now support slicing and negative indices. This makes *range* more |
| interoperable with lists:: |
| |
| >>> range(0, 100, 2).count(10) |
| 1 |
| >>> range(0, 100, 2).index(10) |
| 5 |
| >>> range(0, 100, 2)[5] |
| 10 |
| >>> range(0, 100, 2)[0:5] |
| range(0, 10, 2) |
| |
| (Contributed by Daniel Stuzback in :issue:`9213` and by Alexander Belopolsky |
| in :issue:`2690`.) |
| |
| * The :func:`callable` builtin function from Py2.x was resurrected. It provides |
| a concise, readable alternative to using an :term:`abstract base class` in an |
| expression like ``isinstance(x, collections.Callable)``: |
| |
| >>> callable(max) |
| True |
| >>> callable(20) |
| False |
| |
| (See :issue:`10518`.) |
| |
| * Python's import mechanism can now load module installed in directories with |
| non-ASCII characters in the path name. |
| |
| (Required extensive work by Victor Stinner in :issue:`9425`.) |
| |
| |
| New, Improved, and Deprecated Modules |
| ===================================== |
| |
| * The :mod:`functools` module includes a new decorator for caching function |
| calls. :func:`functools.lru_cache` can save repeated queries to an external |
| resource whenever the results are expected to be the same. |
| |
| For example, adding a caching decorator to a database query function can save |
| database accesses for popular searches:: |
| |
| @functools.lru_cache(maxsize=300) |
| def get_phone_number(name): |
| c = conn.cursor() |
| c.execute('SELECT phonenumber FROM phonelist WHERE name=?', (name,)) |
| return c.fetchone()[0] |
| |
| >>> for name in user_requests: |
| ... get_phone_number(name) # cached lookup |
| |
| To help with choosing an effective cache size, the wrapped function is |
| instrumented for tracking cache statistics: |
| |
| >>> get_phone_number.cache_info() |
| CacheInfo(hits=4805, misses=980, maxsize=300, currsize=300) |
| |
| If the phonelist table gets updated, the outdated contents of the cache can be |
| cleared with: |
| |
| >>> get_phone_number.cache_clear() |
| |
| (Contributed by Raymond Hettinger and incorporating design ideas from |
| Jim Baker, Miki Tebeka, and Nick Coghlan.) |
| |
| * The :func:`functools.wraps` decorator now adds a :attr:`__wrapped__` attribute |
| pointing to the original callable function. This allows wrapped functions to |
| be introspected. It also copies :attr:`__annotations__` if defined. And now |
| it also gracefully skips over missing attributes such as :attr:`__doc__` which |
| might not be defined for the wrapped callable. |
| |
| (By Nick Coghlan and Terrence Cole; :issue:`9567`, :issue:`3445`, and |
| :issue:`8814`.) |
| |
| * The :mod:`itertools` module has a new :func:`~itertools.accumulate` function |
| modeled on APL's *scan* operator and on Numpy's *accumulate* function: |
| |
| >>> list(accumulate(8, 2, 50)) |
| [8, 10, 60] |
| |
| >>> prob_dist = [0.1, 0.4, 0.2, 0.3] |
| >>> list(accumulate(prob_dist)) # cumulative probability distribution |
| [0.1, 0.5, 0.7, 1.0] |
| |
| For an example using :func:`~itertools.accumulate`, see the :ref:`examples for |
| the random module <random-examples>`. |
| |
| (Contributed by Raymond Hettinger and incorporating design suggestions |
| from Mark Dickinson.) |
| |
| * The :class:`collections.Counter` class now has two forms of in-place |
| subtraction, the existing *-=* operator for `saturating subtraction |
| <http://en.wikipedia.org/wiki/Saturation_arithmetic>`_ and the new |
| :meth:`~collections.Counter.subtract` method for regular subtraction. The |
| former is suitable for `multisets <http://en.wikipedia.org/wiki/Multiset>`_ |
| which only have positive counts, and the latter is more suitable for counters |
| that allow negative counts: |
| |
| >>> tally = Counter(dogs=5, cat=3) |
| >>> tally -= Counter(dogs=2, cats=8) # saturating subtraction |
| >>> tally |
| Counter({'dogs': 3}) |
| |
| >>> tally = Counter(dogs=5, cats=3) |
| >>> tally.subtract(dogs=2, cats=8) # regular subtraction |
| >>> tally |
| Counter({'dogs': 3, 'cats': -5}) |
| |
| (Contributed by Raymond Hettinger.) |
| |
| * The :mod:`datetime` module has a new type :class:`~datetime.timezone` that |
| implements the :class:`~datetime.tzinfo` interface by returning a fixed UTC |
| offset and timezone name. This makes it easier to create timezone aware |
| datetime objects: |
| |
| >>> datetime.now(timezone.utc) |
| datetime.datetime(2010, 12, 8, 21, 4, 2, 923754, tzinfo=datetime.timezone.utc) |
| |
| >>> datetime.strptime("01/01/2000 12:00 +0000", "%m/%d/%Y %H:%M %z") |
| datetime.datetime(2000, 1, 1, 12, 0, tzinfo=datetime.timezone.utc) |
| |
| Also, :class:`~datetime.timedelta` objects can now be multiplied by |
| :class:`float` and divided by :class:`float` and :class:`int` objects. |
| |
| (Contributed by Alexander Belopolsky in :issue:`1289118`, :issue:`5094` and |
| :issue:`6641`.) |
| |
| * The :mod:`abc` module now supports :func:`~abc.abstractclassmethod` and |
| :func:`~abc.abstractstaticmethod`. |
| |
| These tools make it possible to define an :term:`Abstract Base Class` that |
| requires a particular :func:`classmethod` or :func:`staticmethod` to be |
| implemented. |
| |
| (Patch submitted by Daniel Urban; :issue:`5867`.) |
| |
| * The :class:`ftplib.FTP` class now supports the context manager protocol to |
| unconditionally consume :exc:`socket.error` exceptions and to close the FTP |
| connection when done:: |
| |
| >>> from ftplib import FTP |
| >>> with FTP("ftp1.at.proftpd.org") as ftp: |
| ... ftp.login() |
| ... ftp.dir() |
| ... |
| '230 Anonymous login ok, restrictions apply.' |
| dr-xr-xr-x 9 ftp ftp 154 May 6 10:43 . |
| dr-xr-xr-x 9 ftp ftp 154 May 6 10:43 .. |
| dr-xr-xr-x 5 ftp ftp 4096 May 6 10:43 CentOS |
| dr-xr-xr-x 3 ftp ftp 18 Jul 10 2008 Fedora |
| |
| Other file-like objects such as :class:`mmap.mmap` and :func:`fileinput.input` |
| also grew auto-closing context managers:: |
| |
| with fileinput.input(files=('log1.txt', 'log2.txt')) as f: |
| for line in f: |
| process(line) |
| |
| (Contributed by Tarek Ziadé and Giampaolo Rodolà in :issue:`4972`, and |
| by Georg Brandl in :issue:`8046` and :issue:`1286`.) |
| |
| .. mention os.popen and subprocess.Popen auto-closing of fds |
| |
| * :class:`gzip.GzipFile` now implements the :class:`io.BufferedIOBase` |
| :term:`abstract base class` (except for ``truncate()``). It also has a |
| :meth:`~gzip.GzipFile.peek` method and supports unseekable as well as |
| zero-padded file objects. |
| |
| The :mod:`gzip` module also gains the :func:`~gzip.compress` and |
| :func:`~gzip.decompress` functions for easier in-memory compression and |
| decompression. Keep in mind that text needs to be encoded in to |
| :class:`bytes` before compressing and decompressing: |
| |
| >>> s = 'Three shall be the number thou shalt count, ' |
| >>> s += 'and the number of the counting shall be three' |
| >>> b = s.encode() # convert to utf-8 |
| >>> len(b) |
| 89 |
| >>> c = gzip.compress(b) |
| >>> len(c) |
| 77 |
| >>> gzip.decompress(c).decode()[:42] # decompress and convert to text |
| 'Three shall be the number thou shalt count,' |
| |
| (Contributed by Anand B. Pillai in :issue:`3488`; and by Antoine Pitrou, Nir |
| Aides and Brian Curtin in :issue:`9962`, :issue:`1675951`, :issue:`7471` and |
| :issue:`2846`.) |
| |
| * The :func:`shutil.copytree` function has two new options: |
| |
| * *ignore_dangling_symlinks*: when ``symlinks=False`` so that the function |
| copies the file pointed to by the symlink, not the symlink itself. This |
| option will silence the error raised if the file doesn't exist. |
| |
| * *copy_function*: is a callable that will be used to copy files. |
| :func:`shutil.copy2` is used by default. |
| |
| (Contributed by Tarek Ziadé.) |
| |
| * Socket objects now have a :meth:`~socket.socket.detach()` method which puts |
| the socket into closed state without actually closing the underlying file |
| descriptor. The latter can then be reused for other purposes. |
| |
| (Added by Antoine Pitrou; :issue:`8524`.) |
| |
| * The :mod:`sqlite3` module has two new capabilities. |
| |
| The :attr:`Connection.in_transit` attribute is true if there is an active |
| transaction for uncommitted changes. |
| |
| The :meth:`Connection.enable_load_extension` and |
| :meth:`Connection.load_extension` methods allows you to load SQLite extensions |
| from ".so" files. One well-known extension is the fulltext-search extension |
| distributed with SQLite. |
| |
| (Contributed by R. David Murray and Shashwat Anand; :issue:`8845`.) |
| |
| * The :mod:`ssl` module has a new class, :class:`~ssl.SSLContext` which serves |
| as a container for various persistent SSL data, such as protocol settings, |
| certificates, private keys, and various other options. The |
| :meth:`~ssl.SSLContext.wrap_socket` method allows to create an SSL socket from |
| such an SSL context. (Added by Antoine Pitrou; :issue:`8550`.) |
| |
| A new function, :func:`ssl.match_hostname`, helps implement server identity |
| verification for higher-level protocols by implementing the rules of |
| HTTPS (from :rfc:`2818`), which are also suitable for other protocols. |
| (Added by Antoine Pitrou, :issue:`1589`). |
| |
| The :func:`ssl.wrap_socket` constructor function now takes a *ciphers* |
| argument that's a string listing the encryption algorithms to be allowed; the |
| format of the string is described `in the OpenSSL documentation |
| <http://www.openssl.org/docs/apps/ciphers.html#CIPHER_LIST_FORMAT>`__. (Added |
| by Antoine Pitrou; :issue:`8322`.) |
| |
| When linked against a recent enough version of OpenSSL, the :mod:`ssl` |
| module now supports the Server Name Indication extension to the TLS |
| protocol, allowing for several "virtual hosts" using different certificates |
| on a single IP/port. This extension is only supported in client mode, |
| and is activated by passing the *server_hostname* argument to |
| :meth:`SSLContext.wrap_socket`. |
| (Added by Antoine Pitrou, :issue:`5639`.) |
| |
| Various options have been added to the :mod:`ssl` module, such as |
| :data:`~ssl.OP_NO_SSLv2` which allows to force disabling of the insecure and |
| obsolete SSLv2 protocol. (Added by Antoine Pitrou; :issue:`4870`.) |
| |
| Another change makes the extension load all of OpenSSL's ciphers and digest |
| algorithms so that they're all available. Some SSL certificates couldn't be |
| verified, reporting an "unknown algorithm" error. (Reported by Beda Kosata, |
| and fixed by Antoine Pitrou; :issue:`8484`.) |
| |
| The version of OpenSSL being used is now available as the module attributes |
| :data:`ssl.OPENSSL_VERSION` (a string), :data:`ssl.OPENSSL_VERSION_INFO` (a |
| 5-tuple), and :data:`ssl.OPENSSL_VERSION_NUMBER` (an integer). (Added by |
| Antoine Pitrou; :issue:`8321`.) |
| |
| * The :mod:`nntplib` module has a revamped implementation with better bytes and |
| unicode semantics as well as more practical APIs. These improvements break |
| compatibility with the nntplib version in Python 3.1, which was partly |
| dysfunctional in itself. |
| |
| (Contributed by Antoine Pitrou in :issue:`9360`) |
| |
| * :class:`http.client.HTTPSConnection`, :class:`urllib.request.HTTPSHandler` |
| and :func:`urllib.request.urlopen` now take optional arguments to allow for |
| server certificate checking against a set of Certificate Authorities, |
| as recommended in public uses of HTTPS. |
| (Added by Antoine Pitrou, :issue:`9003`.) |
| |
| * The command-line call, ``python -m unittest`` can now accept file paths |
| instead of module names for running specific tests (:issue:`10620`). The new |
| test discovery can find tests within packages, locating any test importable |
| from the top level directory. The top level directory can be specified with |
| the `-t` option, a pattern for matching files with ``-p``, and a directory to |
| start discovery with ``-s``:: |
| |
| $ python -m unittest discover -s my_proj_dir -p '_test.py' |
| |
| (Contributed by Michael Foord.) |
| |
| * The :mod:`unittest` module has two new methods, |
| :meth:`~unittest.TestCase.assertWarns` and |
| :meth:`~unittest.TestCase.assertWarnsRegex` to check that a given warning type |
| is triggered by the code under test: |
| |
| >>> with self.assertWarns(DeprecationWarning): |
| ... legacy_function('XYZ') |
| |
| Another new method, :meth:`~unittest.TestCase.assertCountEqual` is used to |
| compare two iterables to determine if their element counts are equal (are the |
| same elements present the same number of times:: |
| |
| def test_anagram(self): |
| self.assertCountEqual('algorithm', 'logarithm') |
| |
| A principal feature of the unittest module is an effort to produce meaningful |
| diagnostics when a test fails. When possible the failure is recorded along |
| with a diff of the output. This is especially helpful for analyzing log files |
| of failed test runs. However, since diffs can sometime be voluminous, there is |
| a new :attr:`~unittest.TestCase.maxDiff` attribute which sets maximum length of |
| diffs. |
| |
| In addition the naming in the module has undergone a number of clean-ups. For |
| example, :meth:`~unittest.TestCase.assertRegex` is the new name for |
| :meth:`~unittest.TestCase.assertRegexpMatches` which was misnamed because the |
| test uses :func:`re.search`, not :func:`re.match`. Other methods using |
| regular expressions are now named using short form "Regex" in preference |
| to "Regexp" -- this matches the names used in other unittest implementations, |
| matches Python's old name for the :mod:`re` module, and it has unambiguous |
| camel-casing. |
| |
| To improve consistency, some of long-standing method aliases are being |
| deprecated in favor of the preferred names: |
| |
| - replace :meth:`assert_` with :meth:`.assertTrue` |
| - replace :meth:`assertEquals` with :meth:`.assertEqual` |
| - replace :meth:`assertNotEquals` with :meth:`.assertNotEqual` |
| - replace :meth:`assertAlmostEquals` with :meth:`.assertAlmostEqual` |
| - replace :meth:`assertNotAlmostEquals` with :meth:`.assertNotAlmostEqual` |
| |
| Likewise, the ``TestCase.fail*`` methods deprecated in Python 3.1 are expected |
| to be removed in Python 3.3. See also the :ref:`deprecated-aliases` section in |
| the :mod:`unittest` documentation. |
| |
| (Contributed by Ezio Melotti; :issue:`9424`.) |
| |
| * :class:`~poplib.POP3_SSL` class now accepts a *context* parameter, which is a |
| :class:`ssl.SSLContext` object allowing bundling SSL configuration options, |
| certificates and private keys into a single (potentially long-lived) |
| structure. |
| |
| (Contributed by Giampaolo Rodolà; :issue:`8807`.) |
| |
| * :func:`socket.create_connection` now supports the context manager protocol |
| to unconditionally consume :exc:`socket.error` exceptions and to close the |
| socket when done. |
| |
| (Contributed by Giampaolo Rodolà; :issue:`9794`.) |
| |
| * :class:`asyncore.dispatcher` now provides a |
| :meth:`~asyncore.dispatcher.handle_accepted()` method |
| returning a `(sock, addr)` pair which is called when a connection has actually |
| been established with a new remote endpoint. This is supposed to be used as a |
| replacement for old :meth:`~asyncore.dispatcher.handle_accept()` and avoids |
| the user to call :meth:`~asyncore.dispatcher.accept()` directly. |
| |
| (Contributed by Giampaolo Rodolà; :issue:`6706`.) |
| |
| * The :mod:`tempfile` module has a new context manager, |
| :class:`~tempfile.TemporaryDirectory` which provides easy deterministic |
| cleanup of temporary directories: |
| |
| >>> with tempfile.TemporaryDirectory() as tmpdirname: |
| ... print 'created temporary directory', tmpdirname |
| |
| (Contributed by Neil Schemenauer and Nick Coghlan; :issue:`5178`.) |
| |
| * The :mod:`inspect` module has a new function :func:`getgenatorstate` |
| to easily identify the current state of a generator as one of |
| ``GEN_CREATED``, ``GEN_RUNNING``, ``GEN_SUSPENDED`` or ``GEN_CLOSED``. |
| |
| (Contributed by Rodolpho Eckhardt and Nick Coghlan, :issue:`10220`.) |
| |
| .. XXX: Create a new section for all changes relating to context managers. |
| .. XXX: Various ConfigParser changes |
| .. XXX: Mention urllib.parse changes |
| Issue 9873 (Nick Coghlan): |
| - ASCII byte sequence support in URL parsing |
| - named tuple for urldefrag return value |
| Issue 5468 (Dan Mahn) for urlencode: |
| - bytes input support |
| - non-UTF8 percent encoding of non-ASCII characters |
| Issue 2987 for IPv6 (RFC2732) support in urlparse |
| |
| * The :mod:`pydoc` module now provides a much improved Web server interface, |
| as well as a new command-line option to automatically open a browser |
| window to display that server. |
| |
| (Contributed by Ron Adam; :issue:`2001`.) |
| |
| * The new :mod:`sysconfig` module makes it straight-forward to discover |
| installation paths and configuration variables which vary across platforms and |
| installs. |
| |
| The module offers access simple access functions for platform and version |
| information: |
| |
| * :func:`~sysconfig.get_platform` returning values like *linux-i586* or |
| *macosx-10.6-ppc*. |
| * :func:`~sysconfig.get_python_version` returns a Python version string in |
| the form, "3.2". |
| |
| It also provides access to the paths and variables corresponding to one of |
| seven named schemes used by :mod:`distutils`. Those include *posix_prefix*, |
| *posix_home*, *posix_user*, *nt*, *nt_user*, *os2*, *os2_home*: |
| |
| * :func:`~sysconfig.get_paths` makes a dictionary containing installation paths |
| for the current installation scheme. |
| * :func:`~sysconfig.get_config_vars` returns a dictionary of platform specific |
| variables. |
| |
| There is also a convenient command-line interface:: |
| |
| C:\Python32>python -m sysconfig |
| Platform: "win32" |
| Python version: "3.2" |
| Current installation scheme: "nt" |
| |
| Paths: |
| data = "C:\Python32" |
| include = "C:\Python32\Include" |
| platinclude = "C:\Python32\Include" |
| platlib = "C:\Python32\Lib\site-packages" |
| platstdlib = "C:\Python32\Lib" |
| purelib = "C:\Python32\Lib\site-packages" |
| scripts = "C:\Python32\Scripts" |
| stdlib = "C:\Python32\Lib" |
| |
| Variables: |
| BINDIR = "C:\Python32" |
| BINLIBDEST = "C:\Python32\Lib" |
| EXE = ".exe" |
| INCLUDEPY = "C:\Python32\Include" |
| LIBDEST = "C:\Python32\Lib" |
| SO = ".pyd" |
| VERSION = "32" |
| abiflags = "" |
| base = "C:\Python32" |
| exec_prefix = "C:\Python32" |
| platbase = "C:\Python32" |
| prefix = "C:\Python32" |
| projectbase = "C:\Python32" |
| py_version = "3.2" |
| py_version_nodot = "32" |
| py_version_short = "3.2" |
| srcdir = "C:\Python32" |
| userbase = "C:\Documents and Settings\Raymond\Application Data\Python" |
| |
| * The :mod:`pdb` debugger module gained a number of usability improvements: |
| |
| - :file:`pdb.py` now has a ``-c`` option that executes commands as given in a |
| :file:`.pdbrc` script file. |
| - A :file:`.pdbrc` script file can contain ``continue`` and ``next`` commands |
| that continue debugging. |
| - The :class:`Pdb` class constructor now accepts a *nosigint* argument. |
| - new commands: ``l(list)``, ``ll(long list`` and ``source`` for |
| listing source code. |
| - new commands: ``display`` and ``undisplay`` for showing or hiding |
| the value of an expression if it has changed. |
| - new command: ``interact`` for starting an interactive interpreter containing |
| the global and local names found in the current scope. |
| - breakpoints can be cleared by breakpoint number |
| |
| |
| Multi-threading |
| =============== |
| |
| * The mechanism for serializing execution of concurrently running Python threads |
| (generally known as the GIL or Global Interpreter Lock) has been rewritten. |
| Among the objectives were more predictable switching intervals and reduced |
| overhead due to lock contention and the number of ensuing system calls. The |
| notion of a "check interval" to allow thread switches has been abandoned and |
| replaced by an absolute duration expressed in seconds. This parameter is |
| tunable through :func:`sys.setswitchinterval()`. It currently defaults to 5 |
| milliseconds. |
| |
| Additional details about the implementation can be read from a `python-dev |
| mailing-list message |
| <http://mail.python.org/pipermail/python-dev/2009-October/093321.html>`_ |
| (however, "priority requests" as exposed in this message have not been kept |
| for inclusion). |
| |
| (Contributed by Antoine Pitrou.) |
| |
| * Regular and recursive locks now accept an optional *timeout* argument to their |
| :meth:`acquire` method. (Contributed by Antoine Pitrou; :issue:`7316`.) |
| |
| Similarly, :meth:`threading.Semaphore.acquire` also gains a *timeout* |
| argument. (Contributed by Torsten Landschoff; :issue:`850728`.) |
| |
| |
| Optimizations |
| ============= |
| |
| A number of small performance enhancements have been added: |
| |
| * Python's peephole optimizer now recognizes patterns such ``x in {1, 2, 3}`` as |
| being a test for membership in a set of constants. The optimizer recasts the |
| :class:`set` as a :class:`frozenset` and stores the pre-built constant. |
| |
| Now that the speed penalty is gone, it is practical to start writing |
| membership tests using set-notation. This style is both semantically clear |
| and operationally fast:: |
| |
| extension = name.rpartition('.')[2] |
| if extension in {'xml', 'html', 'xhtml', 'css'}: |
| handle(name) |
| |
| (Patch and additional tests by Dave Malcolm; :issue:`6690`). |
| |
| * Serializing and unserializing data using the :mod:`pickle` module is now |
| several times faster. |
| |
| (Contributed by Alexandre Vassalotti, Antoine Pitrou |
| and the Unladen Swallow team in :issue:`9410` and :issue:`3873`.) |
| |
| * The `Timsort algorithm <http://en.wikipedia.org/wiki/Timsort>`_ used in |
| :meth:`list.sort` and :func:`sorted` now runs faster and used less memory |
| when called with a :term:`key function`. Previously, every element of |
| a list was wrapped with a temporary object that remembered the key value |
| associated with each element. Now, an array of keys and values are |
| sorted in parallel. This save the memory consumed by the sort wrappers, |
| and it saves time lost from during comparisons which where delegated |
| by the sort wrappers. |
| |
| (Patch by Daniel Stuzback in :issue:`9915`.) |
| |
| * JSON decoding performance is improved and memory consumption is reduced |
| whenever the same string is repeated for multiple keys. Also, JSON encoding |
| now uses the C speedups when the ``sort_keys`` argument is true. |
| |
| (Contributed by Antoine Pitrou in :issue:`7451` and by Raymond Hettinger and |
| Antoine Pitrou in :issue:`10314`.) |
| |
| * Recursive locks (created with the :func:`threading.RLock` API) now benefit |
| from a C implementation which makes them as fast as regular locks, and between |
| 10x and 15x faster than their previous pure Python implementation. |
| |
| (Contributed by Antoine Pitrou; :issue:`3001`.) |
| |
| * The fast-search algorithm in stringlib is now used by the :meth:`split`, |
| :meth:`rsplit`, :meth:`splitlines` and :meth:`replace` methods on |
| :class:`bytes`, :class:`bytearray` and :class:`str` objects. Likewise, the |
| algorithm is also used by :meth:`rfind`, :meth:`rindex`, :meth:`rsplit` and |
| :meth:`rpartition`. |
| |
| (Patch by Florent Xicluna in :issue:`7622` and :issue:`7462`.) |
| |
| There were several other minor optimizations. Set differencing now runs faster |
| when one operand is much larger than the other (Patch by Andress Bennetts in |
| :issue:`8685`). The :meth:`array.repeat` method has a faster implementation |
| (:issue:`1569291` by Alexander Belopolsky). The :class:`BaseHTTPRequestHandler` |
| has more efficient buffering (:issue:`3709` by Andrew Schaaf). The |
| multi-argument form of :func:`operator.attrgetter` now function runs slightly |
| faster (:issue:`10160` by Christos Georgiou). And :class:`ConfigParser` loads |
| multi-line arguments a bit faster (:issue:`7113` by Łukasz Langa). |
| |
| |
| Unicode |
| ======= |
| |
| Python has been updated to Unicode 6.0.0. The new features of the |
| Unicode Standard that will affect Python users include: |
| |
| * addition of 2,088 characters, including over 1,000 additional |
| symbols—chief among them the additional emoji symbols, which are |
| especially important for mobile phones; |
| |
| * changes to character properties for existing characters including |
| |
| - a general category change to two Kannada characters (U+0CF1, |
| U+0CF2), which has the effect of making them newly eligible for |
| inclusion in identifiers; |
| |
| - a general category change to one New Tai Lue numeric character |
| (U+19DA), which has the effect of disqualifying it from |
| inclusion in identifiers. |
| |
| For more information, see `Unicode Character Database Changes |
| <http://www.unicode.org/versions/Unicode6.0.0/#Database_Changes>`_ |
| at the `Unicode Consortium <http://www.unicode.org/>`_ web site. |
| |
| The :mod:`os` module has two new functions: :func:`~os.fsencode` and |
| :func:`~os.fsdecode`. Add :data:`os.environb`: bytes version of |
| :data:`os.environ`, :func:`os.getenvb` function and |
| :data:`os.supports_bytes_environ` constant. |
| |
| ``'mbcs'`` encoding doesn't ignore the error handler argument any more. By |
| default (strict mode), it raises an UnicodeDecodeError on undecodable byte |
| sequence and UnicodeEncodeError on unencodable character. To get the ``'mbcs'`` |
| encoding of Python 3.1, use ``'ignore'`` error handler to decode and |
| ``'replace'`` error handler to encode. ``'mbcs'`` supports ``'strict'`` and |
| ``'ignore'`` error handlers for decoding, and ``'strict'`` and ``'replace'`` |
| for encoding. |
| |
| On Mac OS X, Python uses ``'utf-8'`` to decode the command line arguments, |
| instead of the locale encoding (which is ISO-8859-1 if the ``LANG`` environment |
| variable is not set). |
| |
| By default, tarfile uses ``'utf-8'`` encoding on Windows (instead of |
| ``'mbcs'``), and the ``'surrogateescape'`` error handler on all operating |
| systems. |
| |
| |
| Documentation |
| ============= |
| |
| The documentation continues to be improved. |
| |
| A table of quick links has been added to the top of lengthy sections such as |
| :ref:`built-in-funcs`. In the case of :mod:`itertools`, the links are |
| accompanied by tables of cheatsheet-style summaries to provide an overview and |
| memory jog without having to read all of the docs. |
| |
| In some cases, the pure python source code can be helpful adjunct to the docs, |
| so now some modules feature quick links to the latest version of the source |
| code. For example, the :mod:`functools` module documentation has a quick link |
| at the top labeled :source:`functools Python source code <Lib/functools.py>`. |
| |
| The docs now contain more examples and recipes. In particular, :mod:`re` module |
| has an extensive section, :ref:`re-examples`. Likewise, the :mod:`itertools` |
| module continues to be updated with new :ref:`itertools-recipes`. |
| |
| The :mod:`datetime` module now has an auxiliary implementation in pure Python. |
| No functionality was changed. This just provides an easier-to-read |
| alternate implementation. (Contributed by Alexander Belopolsky.) |
| |
| |
| IDLE |
| ==== |
| |
| * The format menu now has an option to clean-up source files by stripping |
| trailing whitespace (:issue:`5150`). |
| |
| |
| Build and C API Changes |
| ======================= |
| |
| Changes to Python's build process and to the C API include: |
| |
| * The C functions that access the Unicode Database now accept and return |
| characters from the full Unicode range, even on narrow unicode builds |
| (Py_UNICODE_TOLOWER, Py_UNICODE_ISDECIMAL, and others). A visible difference |
| in Python is that :func:`unicodedata.numeric` now returns the correct value |
| for large code points, and :func:`repr` may consider more characters as |
| printable. |
| |
| (Reported by Bupjoe Lee and fixed by Amaury Forgeot D'Arc; :issue:`5127`.) |
| |
| * Computed gotos are now enabled by default on supported compilers (which are |
| detected by the configure script). They can still be disabled selectively by |
| specifying ``--without-computed-gotos``. |
| |
| (Contributed by Antoine Pitrou; :issue:`9203`.) |
| |
| * The option ``--with-wctype-functions`` was removed. The built-in unicode |
| database is now used for all functions. |
| |
| (Contributed by Amaury Forgeot D'Arc; :issue:`9210`.) |
| |
| * Hash values are now values of a new type, Py_hash_t, which is defined to |
| be the same size as a pointer. Previously they were of type long, which |
| on some 64-bit operating systems is still only 32 bits long. As a result |
| of this fix, :class:`set` and :class:`dict` can now hold more than ``2**32`` |
| entries on builds with 64-bit pointers (previously, they could grow to |
| that size but their performance degraded catastrophically). |
| |
| (Contributed by Benjamin Peterson; :issue:`9778`.) |
| |
| |
| Porting to Python 3.2 |
| ===================== |
| |
| This section lists previously described changes and other bugfixes that may |
| require changes to your code: |
| |
| * The :mod:`nntplib` module was reworked extensively, meaning that its APIs |
| are often incompatible with the 3.1 APIs. |
| |
| * :class:`bytearray` objects can no longer be used as filenames; instead, |
| they should be converted to :class:`bytes`. |
| |
| * PyArg_Parse*() functions: |
| |
| * "t#" format has been removed: use "s#" or "s*" instead |
| * "w" and "w#" formats has been removed: use "w*" instead |
| |
| * The :c:type:`PyCObject` type, deprecated in 3.1, has been removed. To wrap |
| opaque C pointers in Python objects, the :c:type:`PyCapsule` API should be used |
| instead; the new type has a well-defined interface for passing typing safety |
| information and a less complicated signature for calling a destructor. |
| |
| * The :func:`sys.setfilesystemencoding` function was removed because |
| it had a flawed design. |
| |
| * The :func:`random.seed` function and method now performing salting for |
| string seeds. To access the previous version of *seed* in order to |
| reproduce Python 3.1 sequences, set the *version* argument to *1*, |
| ``random.seed(s, version=1)``. |
| |
| * The previously deprecated :func:`string.maketrans` function has been removed |
| in favor of the static methods, :meth:`bytes.maketrans` and |
| :meth:`bytearray.maketrans`. This change solves the confusion around which |
| types were supported by the :mod:`string` module. Now, :class:`str`, |
| :class:`bytes`, and :class:`bytearray` each have their own **maketrans** and |
| **translate** methods with intermediate translation tables of the appropriate |
| type. |
| |
| (Contributed by Georg Brandl; :issue:`5675`.) |
| |
| * The previously deprecated :func:`contextlib.nested` function has been removed |
| in favor of a plain :keyword:`with` statement which can accept multiple |
| context managers. The latter technique is faster (because it is built-in), |
| and it does a better job finalizing multiple context managers when one of them |
| raises an exception:: |
| |
| >>> with open('mylog.txt') as infile, open('a.out', 'w') as outfile: |
| ... for line in infile: |
| ... if '<critical>' in line: |
| ... outfile.write(line) |
| |
| (Contributed by Georg Brandl and Mattias Brändström; |
| `appspot issue 53094 <http://codereview.appspot.com/53094>`_.) |