| **************************** |
| 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 bug/patch number as a comment: |
| |
| % Patch 12345 |
| XXX Describe the transmogrify() function added to the socket |
| module. |
| (Contributed by P.Y. Developer.) |
| |
| 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 XXX: Stub |
| ============= |
| |
| |
| Other Language Changes |
| ====================== |
| |
| Some smaller changes made to the core Python language are: |
| |
| * Stub |
| |
| |
| New, Improved, and Deprecated Modules |
| ===================================== |
| |
| * The functools module now includes two new decorators for caching function |
| calls, :func:`functools.lru_cache` and :func:`functools.lfu_cache`. These 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.lfu_cache(maxsize=50) |
| def get_phone_number(name): |
| c = conn.cursor() |
| c.execute('SELECT phonenumber FROM phonelist WHERE name=?', (name,)) |
| return c.fetchone()[0] |
| |
| The caches support two strategies for limiting their size to *maxsize*. The |
| LFU (least-frequently-used) cache works bests when popular queries remain the |
| same over time. In contrast, the LRU (least-recently-used) cache works best |
| query popularity changes over time (for example, the most popular news |
| articles change each day as newer articles are added). |
| |
| The two caching decorators can be composed (nested) to handle hybrid cases. |
| For example, music searches can reflect both long-term patterns (popular |
| classics) and short-term trends (new releases):: |
| |
| @functools.lfu_cache(maxsize=500) |
| @functools.lru_cache(maxsize=100) |
| def find_lyrics(song): |
| query = 'http://www.example.com/songlist/%s' % urllib.quote(song) |
| page = urllib.urlopen(query).read() |
| return parse_lyrics(page) |
| |
| To help with choosing an effective cache size, the wrapped function |
| is instrumented with two attributes *hits* and *misses*:: |
| |
| >>> for song in user_requests: |
| ... find_lyrics(song) |
| >>> print(find_lyrics.hits, find_lyrics.misses) |
| 4805 980 |
| |
| (Contributed by Raymond Hettinger) |
| |
| * 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 |
| (Contributed by Tarek Ziadé and Giampaolo Rodolà; :issue:`4972`.) |
| |
| * A warning message will now get printed at interpreter shutdown if |
| the :data:`gc.garbage` list isn't empty. This is meant to make the |
| programmer aware that his code contains object finalization issues. |
| (Added by Antoine Pitrou; :issue:`477863`.) |
| |
| * The :func:`shutil.copytree` function has two new options: |
| |
| * *ignore_dangling_symlinks*: when ``symlinks=False`` (meaning 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*: 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.forget()` 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 *sqlite3* module has some new features: |
| |
| * XXX *enable_load_extension* |
| |
| * XXX *load_extension* |
| |
| * New :class:`~sqlite3.Connection` attribute |
| :attr:`~sqlite3.Connection.in_transaction` is :const:`True` when there |
| are uncommitted changes, and :const:`False` otherwise. (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`.) |
| |
| 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`.) |
| |
| 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 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`.) |
| |
| |
| 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 ``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 |
| ============= |
| |
| Major performance enhancements have been added: |
| |
| * Stub |
| |
| IDLE |
| ==== |
| |
| * Stub |
| |
| |
| Build and C API Changes |
| ======================= |
| |
| Changes to Python's build process and to the C API include: |
| |
| * Stub |
| |
| |
| Porting to Python 3.2 |
| ===================== |
| |
| This section lists previously described changes and other bugfixes |
| that may require changes to your code: |
| |
| * bytearray objects cannot be used anymore as filenames: convert them to bytes |
| |
| * PyArg_Parse*() functions: |
| |
| * "t#" format has been removed: use "s#" or "s*" instead |
| * "w" and "w#" formats has been removed: use "w*" instead |
| |