| **************************** |
| 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 to some degree. |
| |
| * 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. |
| |
| |
| 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 "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 |
| ============================================ |
| |
| .. (Stub section) |
| |
| |
| 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 5.1 |
| ========= |
| |
| The email package is extended to be able 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 Content-Transfer-Encoding. |
| |
| * 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. |
| |
| (Proposed and implemented by R. David Murray, :issue:`4661`.) |
| |
| |
| Other Language Changes |
| ====================== |
| |
| Some smaller changes made to the core Python language are: |
| |
| * 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. |
| |
| (Discovered by Yury Selivanov and fixed by Benjamin Peterson; :issue:`9666`.) |
| |
| * 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:`release()` method and support |
| the context manager protocol. This allows timely release of any resources |
| that were acquired when requesting a buffer from the original object. |
| |
| (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 certain potential issues with resource consumption or cleanup |
| are detected. It is silenced by default in normal release builds, but |
| can be easily enabled through the means provided by the :mod:`warnings` |
| module, or on the command line. |
| |
| :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. |
| |
| (Added by Antoine Pitrou and Georg Brandl; :issue:`477863`.) |
| |
| :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 -Wdefault |
| Python 3.2a3+ (py3k, Nov 5 2010, 22:58:04) |
| [GCC 4.4.3] on linux2 |
| Type "help", "copyright", "credits" or "license" for more information. |
| >>> f = open("foo", "wb") |
| >>> del f |
| __main__:1: ResourceWarning: unclosed file <_io.BufferedWriter name='foo'> |
| >>> |
| |
| (Added by Antoine Pitrou, :issue:`10093`.) |
| |
| |
| New, Improved, and Deprecated Modules |
| ===================================== |
| |
| * XXX mention :mod:`argparse`. |
| |
| * 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] |
| |
| To help with choosing an effective cache size, the wrapped function is |
| instrumented with two attributes *cache_hits* and *cache_misses*: |
| |
| >>> for name in user_requests: |
| ... get_phone_number(name) |
| >>> print(get_phone_number.cache_hits, get_phone_number.cache_misses) |
| 4805 980 |
| |
| 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.) |
| |
| * 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:`nntplib` module gets a revamped implementation with better |
| bytes / 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`) |
| |
| * The :mod:`abc` module now supports :func:`~abc.abstractclassmethod` and |
| :func:`~abc.abstractstaticmethod`. |
| |
| (Patch submitted by Daniel Urban; :issue:`5867`.) |
| |
| * 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. |
| |
| (Contributed by Georg Brandl and Mattias Brändström; |
| `appspot issue 53094 <http://codereview.appspot.com/53094>`_.) |
| |
| * 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`.) |
| |
| * :class:`gzip.GzipFile` now implements the :class:`io.BufferedIOBase` ABC |
| (except for ``truncate()``), has a :meth:`~gzip.GzipFile.peek` method, |
| and supports unseekable as well as zero-padded file objects. |
| |
| (Contributed by Antoine Pitrou, Nir Aides and Brian Curtin in :issue:`9962`, |
| :issue:`1675951`, :issue:`7471` and :issue:`2846`.) |
| |
| The :mod:`gzip` module also gains the :func:`~gzip.compress` and |
| :func:`~gzip.decompress` functions for easier in-memory compression and |
| decompression. |
| |
| (Contributed by Anand B. Pillai in :issue:`3488`.) |
| |
| * The :mod:`os` module now has the :const:`ST_RDONLY` and :const:`ST_NOSUID` |
| constants, for use with the :func:`~os.statvfs` function. |
| |
| (Patch by Adam Jackson; :issue:`7647`.) |
| |
| * :func:`os.getppid` is now supported on Windows. Note that it will continue to |
| return the same pid even after the parent process has exited. |
| |
| (Patch by Jon Anglin; :issue:`6394`.) |
| |
| * 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`.) |
| |
| * :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`.) |
| |
| * Instances of :class:`unittest.TestCase` have two new methods |
| :meth:`~unittest.TestCase.assertWarns` and :meth:`~unittest.TestCase.assertWarnsRegexp` |
| to check that a given warning type was triggered by the code under test:: |
| |
| with self.assertWarns(DeprecationWarning): |
| legacy_function('XYZ') |
| |
| * The following :class:`unittest.TestCase` methods are now deprecated: |
| * :meth:`assert_` (use :meth:`.assertTrue` instead); |
| * :meth:`assertEquals` (use :meth:`.assertEqual` instead); |
| * :meth:`assertNotEquals` (use :meth:`.assertNotEqual` instead); |
| * :meth:`assertAlmostEquals` (use :meth:`.assertAlmostEqual` instead); |
| * :meth:`assertNotAlmostEquals` (use :meth:`.assertNotAlmostEqual` instead); |
| |
| The ``TestCase.fail*`` methods deprecated in Python 3.1 will be removed in |
| Python 3.3. See also the :ref:`deprecated-aliases` section in the |
| :mod:`unittest` documentation. |
| |
| (Contributed by Ezio Melotti; :issue:`9424`.) |
| |
| * 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`.) |
| |
| * :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. |
| |
| (Contributed by Neil Schemenauer and Nick Coghlan; :issue:`5178`.) |
| |
| * 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. |
| |
| (Contributed by R. David Murray, :issue:`10321`.) |
| |
| |
| * 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: Mention inspect.getattr_static (Michael Foord) |
| |
| 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.) |
| |
| * 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`.) |
| |
| * 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: |
| |
| * JSON decoding performance is improved and memory consumption is reduced |
| whenever the same string is repeated for multiple keys. |
| |
| (Contributed by Antoine Pitrou; :issue:`7451`.) |
| |
| * JSON encoding now uses the C speedups also when the ``sort_keys`` argument |
| is true. |
| |
| (Contributed by Raymond Hettinger and Antoine Pitrou, :issue:`10314`.) |
| |
| * 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`). |
| |
| * 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`.) |
| |
| * 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`.) |
| |
| |
| Unicode |
| ======= |
| |
| 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. |
| |
| |
| .. IDLE |
| ==== |
| |
| * Stub |
| |
| |
| 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. |
| |
| (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 cannot be used any more as filenames: convert them |
| 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. |
| |
| * Remove sys.setfilesystemencoding() function: it was broken by design. |