| **************************** |
| What's New In Python 3.2 |
| **************************** |
| |
| :Author: Raymond Hettinger |
| |
| .. $Id$ |
| 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. (Note, during release candidate phase or just before |
| a beta release, please use the tracker instead -- this helps avoid |
| merge conflicts. If you must add a suggested entry directly, |
| please put it in an XXX comment and the maintainer will take notice). |
| |
| * 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 as compared to 3.1. It |
| focuses on a few highlights and gives a few examples. For full details, see the |
| `Misc/NEWS <https://hg.python.org/cpython/file/3.2/Misc/NEWS>`_ file. |
| |
| .. seealso:: |
| |
| :pep:`392` - Python 3.2 Release Schedule |
| |
| |
| 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 had widespread 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'], # three allowed values |
| help = 'action on each target') # help msg |
| parser.add_argument('targets', |
| metavar = 'HOSTNAME', # var name used in help msg |
| nargs = '+', # require one or more targets |
| help = 'url for target machines') # help msg explanation |
| parser.add_argument('-u', '--user', # -u or --user option |
| required = True, # make it 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()) |
| >>> 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', '--missiles', action='store_true') |
| parser_l.add_argument('-t', '--torpedos', action='store_true') |
| |
| parser_m = subparsers.add_parser('move', help='Move Vessel', # second subgroup |
| aliases=('steer', 'turn')) # equivalent names |
| parser_m.add_argument('-c', '--course', type=int, required=True) |
| parser_m.add_argument('-s', '--speed', type=int, default=0) |
| |
| .. code-block:: shell-session |
| |
| $ ./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 steer --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 be |
| loaded and called with code like this:: |
| |
| >>> import json, logging.config |
| >>> with open('conf.json') as f: |
| ... conf = json.load(f) |
| ... |
| >>> logging.config.dictConfig(conf) |
| >>> logging.info("Transaction completed normally") |
| INFO : root : Transaction completed normally |
| >>> logging.critical("Abnormal termination") |
| 2011-02-17 11:14:36,694 root 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 top-level |
| 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 the |
| *java.util.concurrent* package. In that model, a running call and its result |
| are represented by a :class:`~concurrent.futures.Future` object that 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 in 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 concurrent.futures, shutil |
| with concurrent.futures.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 Brian 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__ # doctest: +SKIP |
| '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() # doctest: +SKIP |
| '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') # doctest: +SKIP |
| '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. The command-line |
| invocation of *compileall* has new options: ``-i`` for |
| specifying a list of files and directories to compile and ``-b`` which causes |
| bytecode files to be written to their legacy location rather than |
| *__pycache__*. |
| |
| * The :mod:`importlib.abc` module has been updated with new :term:`abstract base |
| classes <abstract base class>` for loading bytecode files. The obsolete |
| ABCs, :class:`~importlib.abc.PyLoader` and |
| :class:`~importlib.abc.PyPycLoader`, have been deprecated (instructions on how |
| to stay Python 3.1 compatible are included with the documentation). |
| |
| .. 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('EXT_SUFFIX') # find the full filename extension |
| '.cpython-32mu.so' |
| |
| .. seealso:: |
| |
| :pep:`3149` - ABI Version Tagged .so Files |
| PEP written by Barry Warsaw. |
| |
| |
| PEP 3333: Python Web Server Gateway Interface v1.0.1 |
| ===================================================== |
| |
| This informational PEP clarifies how bytes/text issues are to be handled by the |
| WSGI protocol. The challenge is that string handling in Python 3 is most |
| conveniently handled with the :class:`str` type even though the HTTP protocol |
| is itself bytes oriented. |
| |
| The PEP differentiates so-called *native strings* that are used for |
| request/response headers and metadata versus *byte strings* which are used for |
| the bodies of requests and responses. |
| |
| The *native strings* are always of type :class:`str` but are restricted to code |
| points between *U+0000* through *U+00FF* which are translatable to bytes using |
| *Latin-1* encoding. These strings are used for the keys and values in the |
| environment dictionary and for response headers and statuses in the |
| :func:`start_response` function. They must follow :rfc:`2616` with respect to |
| encoding. That is, they must either be *ISO-8859-1* characters or use |
| :rfc:`2047` MIME encoding. |
| |
| For developers porting WSGI applications from Python 2, here are the salient |
| points: |
| |
| * If the app already used strings for headers in Python 2, no change is needed. |
| |
| * If instead, the app encoded output headers or decoded input headers, then the |
| headers will need to be re-encoded to Latin-1. For example, an output header |
| encoded in utf-8 was using ``h.encode('utf-8')`` now needs to convert from |
| bytes to native strings using ``h.encode('utf-8').decode('latin-1')``. |
| |
| * Values yielded by an application or sent using the :meth:`write` method |
| must be byte strings. The :func:`start_response` function and environ |
| must use native strings. The two cannot be mixed. |
| |
| For server implementers writing CGI-to-WSGI pathways or other CGI-style |
| protocols, the users must to be able access the environment using native strings |
| even though the underlying platform may have a different convention. To bridge |
| this gap, the :mod:`wsgiref` module has a new function, |
| :func:`wsgiref.handlers.read_environ` for transcoding CGI variables from |
| :attr:`os.environ` into native strings and returning a new dictionary. |
| |
| .. seealso:: |
| |
| :pep:`3333` - Python Web Server Gateway Interface v1.0.1 |
| PEP written by Phillip Eby. |
| |
| |
| 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`.) |
| |
| * There is also a new :meth:`str.format_map` method that extends the |
| capabilities of the existing :meth:`str.format` method by accepting arbitrary |
| :term:`mapping` objects. This new method makes it possible to use string |
| formatting with any of Python's many dictionary-like objects such as |
| :class:`~collections.defaultdict`, :class:`~shelve.Shelf`, |
| :class:`~configparser.ConfigParser`, or :mod:`dbm`. It is also useful with |
| custom :class:`dict` subclasses that normalize keys before look-up or that |
| supply a :meth:`__missing__` method for unknown keys:: |
| |
| >>> import shelve |
| >>> d = shelve.open('tmp.shl') |
| >>> 'The {project_name} status is {status} as of {date}'.format_map(d) |
| 'The testing project status is green as of February 15, 2011' |
| |
| >>> class LowerCasedDict(dict): |
| ... def __getitem__(self, key): |
| ... return dict.__getitem__(self, key.lower()) |
| >>> lcd = LowerCasedDict(part='widgets', quantity=10) |
| >>> 'There are {QUANTITY} {Part} in stock'.format_map(lcd) |
| 'There are 10 widgets in stock' |
| |
| >>> class PlaceholderDict(dict): |
| ... def __missing__(self, key): |
| ... return '<{}>'.format(key) |
| >>> 'Hello {name}, welcome to {location}'.format_map(PlaceholderDict()) |
| 'Hello <name>, welcome to <location>' |
| |
| (Suggested by Raymond Hettinger and implemented by Eric Smith in |
| :issue:`6081`.) |
| |
| * The interpreter can now be started with a quiet option, ``-q``, to prevent |
| the copyright and version information from being displayed in the interactive |
| mode. The option can be introspected using the :attr:`sys.flags` attribute: |
| |
| .. code-block:: shell-session |
| |
| $ python -q |
| >>> sys.flags |
| sys.flags(debug=0, division_warning=0, inspect=0, interactive=0, |
| optimize=0, dont_write_bytecode=0, no_user_site=0, no_site=0, |
| ignore_environment=0, verbose=0, bytes_warning=0, quiet=1) |
| |
| (Contributed by Marcin Wojdyr in :issue:`1772833`). |
| |
| * The :func:`hasattr` function works by calling :func:`getattr` and detecting |
| whether an exception is raised. This technique allows it to detect methods |
| created dynamically by :meth:`__getattr__` or :meth:`__getattribute__` which |
| would otherwise be absent from the class dictionary. Formerly, *hasattr* |
| would catch any exception, possibly masking genuine errors. Now, *hasattr* |
| has been tightened to only catch :exc:`AttributeError` and let other |
| exceptions pass through:: |
| |
| >>> class A: |
| ... @property |
| ... def f(self): |
| ... return 1 // 0 |
| ... |
| >>> a = A() |
| >>> hasattr(a, 'f') |
| Traceback (most recent call last): |
| ... |
| ZeroDivisionError: integer division or modulo by zero |
| |
| (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: |
| |
| >>> import math |
| >>> 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 management 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`.) |
| |
| * 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`.) |
| |
| * The internal :c:type:`structsequence` tool now creates subclasses of tuple. |
| This means that C structures like those returned by :func:`os.stat`, |
| :func:`time.gmtime`, and :attr:`sys.version_info` now work like a |
| :term:`named tuple` and now work with functions and methods that |
| expect a tuple as an argument. This is a big step forward in making the C |
| structures as flexible as their pure Python counterparts: |
| |
| >>> import sys |
| >>> isinstance(sys.version_info, tuple) |
| True |
| >>> 'Version %d.%d.%d %s(%d)' % sys.version_info # doctest: +SKIP |
| 'Version 3.2.0 final(0)' |
| |
| (Suggested by Arfrever Frehtes Taifersar Arahesis and implemented |
| by Benjamin Peterson in :issue:`8413`.) |
| |
| * Warnings are now easier to control using the :envvar:`PYTHONWARNINGS` |
| environment variable as an alternative to using ``-W`` at the command line: |
| |
| .. code-block:: shell-session |
| |
| $ export PYTHONWARNINGS='ignore::RuntimeWarning::,once::UnicodeWarning::' |
| |
| (Suggested by Barry Warsaw and implemented by Philip Jenvey in :issue:`7301`.) |
| |
| * 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, and if :attr:`gc.DEBUG_UNCOLLECTABLE` is |
| set, all uncollectable objects are printed. 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: |
| |
| .. code-block:: shell-session |
| |
| $ 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, even with values larger than |
| :attr:`sys.maxsize`. 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 Stutzbach in :issue:`9213`, by Alexander Belopolsky |
| in :issue:`2690`, and by Nick Coghlan in :issue:`10889`.) |
| |
| * 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 modules installed in directories with |
| non-ASCII characters in the path name. This solved an aggravating problem |
| with home directories for users with non-ASCII characters in their usernames. |
| |
| (Required extensive work by Victor Stinner in :issue:`9425`.) |
| |
| |
| New, Improved, and Deprecated Modules |
| ===================================== |
| |
| Python's standard library has undergone significant maintenance efforts and |
| quality improvements. |
| |
| The biggest news for Python 3.2 is that the :mod:`email` package, :mod:`mailbox` |
| module, and :mod:`nntplib` modules now work correctly with the bytes/text model |
| in Python 3. For the first time, there is correct handling of messages with |
| mixed encodings. |
| |
| Throughout the standard library, there has been more careful attention to |
| encodings and text versus bytes issues. In particular, interactions with the |
| operating system are now better able to exchange non-ASCII data using the |
| Windows MBCS encoding, locale-aware encodings, or UTF-8. |
| |
| Another significant win is the addition of substantially better support for |
| *SSL* connections and security certificates. |
| |
| In addition, more classes now implement a :term:`context manager` to support |
| convenient and reliable resource clean-up using a :keyword:`with` statement. |
| |
| 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`. |
| |
| Headers with unencoded non-ASCII bytes are deemed to be :rfc:`2047`\ -encoded |
| using the *unknown-8bit* character set. |
| |
| * 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. |
| |
| (Proposed and implemented by R. David Murray, :issue:`4661` and :issue:`10321`.) |
| |
| elementtree |
| ----------- |
| |
| The :mod:`xml.etree.ElementTree` package and its :mod:`xml.etree.cElementTree` |
| counterpart have been updated to version 1.3. |
| |
| Several new and useful functions and methods have been added: |
| |
| * :func:`xml.etree.ElementTree.fromstringlist` which builds an XML document |
| from a sequence of fragments |
| * :func:`xml.etree.ElementTree.register_namespace` for registering a global |
| namespace prefix |
| * :func:`xml.etree.ElementTree.tostringlist` for string representation |
| including all sublists |
| * :meth:`xml.etree.ElementTree.Element.extend` for appending a sequence of zero |
| or more elements |
| * :meth:`xml.etree.ElementTree.Element.iterfind` searches an element and |
| subelements |
| * :meth:`xml.etree.ElementTree.Element.itertext` creates a text iterator over |
| an element and its subelements |
| * :meth:`xml.etree.ElementTree.TreeBuilder.end` closes the current element |
| * :meth:`xml.etree.ElementTree.TreeBuilder.doctype` handles a doctype |
| declaration |
| |
| Two methods have been deprecated: |
| |
| * :meth:`xml.etree.ElementTree.getchildren` use ``list(elem)`` instead. |
| * :meth:`xml.etree.ElementTree.getiterator` use ``Element.iter`` instead. |
| |
| For details of the update, see `Introducing ElementTree |
| <http://effbot.org/zone/elementtree-13-intro.htm>`_ on Fredrik Lundh's website. |
| |
| (Contributed by Florent Xicluna and Fredrik Lundh, :issue:`6472`.) |
| |
| functools |
| --------- |
| |
| * 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: |
| |
| >>> import functools |
| >>> @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: # doctest: +SKIP |
| ... 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() # doctest: +SKIP |
| 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; see `recipe 498245 |
| <https://code.activestate.com/recipes/498245>`_\, `recipe 577479 |
| <https://code.activestate.com/recipes/577479>`_\, :issue:`10586`, and |
| :issue:`10593`.) |
| |
| * 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. |
| |
| In the above example, the cache can be removed by recovering the original |
| function: |
| |
| >>> get_phone_number = get_phone_number.__wrapped__ # uncached function |
| |
| (By Nick Coghlan and Terrence Cole; :issue:`9567`, :issue:`3445`, and |
| :issue:`8814`.) |
| |
| * To help write classes with rich comparison methods, a new decorator |
| :func:`functools.total_ordering` will use existing equality and inequality |
| methods to fill in the remaining methods. |
| |
| For example, supplying *__eq__* and *__lt__* will enable |
| :func:`~functools.total_ordering` to fill-in *__le__*, *__gt__* and *__ge__*:: |
| |
| @total_ordering |
| class Student: |
| def __eq__(self, other): |
| return ((self.lastname.lower(), self.firstname.lower()) == |
| (other.lastname.lower(), other.firstname.lower())) |
| |
| def __lt__(self, other): |
| return ((self.lastname.lower(), self.firstname.lower()) < |
| (other.lastname.lower(), other.firstname.lower())) |
| |
| With the *total_ordering* decorator, the remaining comparison methods |
| are filled in automatically. |
| |
| (Contributed by Raymond Hettinger.) |
| |
| * To aid in porting programs from Python 2, the :func:`functools.cmp_to_key` |
| function converts an old-style comparison function to |
| modern :term:`key function`: |
| |
| >>> # locale-aware sort order |
| >>> sorted(iterable, key=cmp_to_key(locale.strcoll)) # doctest: +SKIP |
| |
| For sorting examples and a brief sorting tutorial, see the `Sorting HowTo |
| <https://wiki.python.org/moin/HowTo/Sorting/>`_ tutorial. |
| |
| (Contributed by Raymond Hettinger.) |
| |
| itertools |
| --------- |
| |
| * The :mod:`itertools` module has a new :func:`~itertools.accumulate` function |
| modeled on APL's *scan* operator and Numpy's *accumulate* function: |
| |
| >>> from itertools import accumulate |
| >>> 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.) |
| |
| collections |
| ----------- |
| |
| * The :class:`collections.Counter` class now has two forms of in-place |
| subtraction, the existing *-=* operator for `saturating subtraction |
| <https://en.wikipedia.org/wiki/Saturation_arithmetic>`_ and the new |
| :meth:`~collections.Counter.subtract` method for regular subtraction. The |
| former is suitable for `multisets <https://en.wikipedia.org/wiki/Multiset>`_ |
| which only have positive counts, and the latter is more suitable for use cases |
| that allow negative counts: |
| |
| >>> from collections import Counter |
| >>> tally = Counter(dogs=5, cats=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 :class:`collections.OrderedDict` class has a new method |
| :meth:`~collections.OrderedDict.move_to_end` which takes an existing key and |
| moves it to either the first or last position in the ordered sequence. |
| |
| The default is to move an item to the last position. This is equivalent of |
| renewing an entry with ``od[k] = od.pop(k)``. |
| |
| A fast move-to-end operation is useful for resequencing entries. For example, |
| an ordered dictionary can be used to track order of access by aging entries |
| from the oldest to the most recently accessed. |
| |
| >>> from collections import OrderedDict |
| >>> d = OrderedDict.fromkeys(['a', 'b', 'X', 'd', 'e']) |
| >>> list(d) |
| ['a', 'b', 'X', 'd', 'e'] |
| >>> d.move_to_end('X') |
| >>> list(d) |
| ['a', 'b', 'd', 'e', 'X'] |
| |
| (Contributed by Raymond Hettinger.) |
| |
| * The :class:`collections.deque` class grew two new methods |
| :meth:`~collections.deque.count` and :meth:`~collections.deque.reverse` that |
| make them more substitutable for :class:`list` objects: |
| |
| >>> from collections import deque |
| >>> d = deque('simsalabim') |
| >>> d.count('s') |
| 2 |
| >>> d.reverse() |
| >>> d |
| deque(['m', 'i', 'b', 'a', 'l', 'a', 's', 'm', 'i', 's']) |
| |
| (Contributed by Raymond Hettinger.) |
| |
| threading |
| --------- |
| |
| The :mod:`threading` module has a new :class:`~threading.Barrier` |
| synchronization class for making multiple threads wait until all of them have |
| reached a common barrier point. Barriers are useful for making sure that a task |
| with multiple preconditions does not run until all of the predecessor tasks are |
| complete. |
| |
| Barriers can work with an arbitrary number of threads. This is a generalization |
| of a `Rendezvous <https://en.wikipedia.org/wiki/Synchronous_rendezvous>`_ which |
| is defined for only two threads. |
| |
| Implemented as a two-phase cyclic barrier, :class:`~threading.Barrier` objects |
| are suitable for use in loops. The separate *filling* and *draining* phases |
| assure that all threads get released (drained) before any one of them can loop |
| back and re-enter the barrier. The barrier fully resets after each cycle. |
| |
| Example of using barriers:: |
| |
| from threading import Barrier, Thread |
| |
| def get_votes(site): |
| ballots = conduct_election(site) |
| all_polls_closed.wait() # do not count until all polls are closed |
| totals = summarize(ballots) |
| publish(site, totals) |
| |
| all_polls_closed = Barrier(len(sites)) |
| for site in sites: |
| Thread(target=get_votes, args=(site,)).start() |
| |
| In this example, the barrier enforces a rule that votes cannot be counted at any |
| polling site until all polls are closed. Notice how a solution with a barrier |
| is similar to one with :meth:`threading.Thread.join`, but the threads stay alive |
| and continue to do work (summarizing ballots) after the barrier point is |
| crossed. |
| |
| If any of the predecessor tasks can hang or be delayed, a barrier can be created |
| with an optional *timeout* parameter. Then if the timeout period elapses before |
| all the predecessor tasks reach the barrier point, all waiting threads are |
| released and a :exc:`~threading.BrokenBarrierError` exception is raised:: |
| |
| def get_votes(site): |
| ballots = conduct_election(site) |
| try: |
| all_polls_closed.wait(timeout=midnight - time.now()) |
| except BrokenBarrierError: |
| lockbox = seal_ballots(ballots) |
| queue.put(lockbox) |
| else: |
| totals = summarize(ballots) |
| publish(site, totals) |
| |
| In this example, the barrier enforces a more robust rule. If some election |
| sites do not finish before midnight, the barrier times-out and the ballots are |
| sealed and deposited in a queue for later handling. |
| |
| See `Barrier Synchronization Patterns |
| <https://parlab.eecs.berkeley.edu/wiki/_media/patterns/paraplop_g1_3.pdf>`_ for |
| more examples of how barriers can be used in parallel computing. Also, there is |
| a simple but thorough explanation of barriers in `The Little Book of Semaphores |
| <http://greenteapress.com/semaphores/downey08semaphores.pdf>`_, *section 3.6*. |
| |
| (Contributed by Kristján Valur Jónsson with an API review by Jeffrey Yasskin in |
| :issue:`8777`.) |
| |
| datetime and time |
| ----------------- |
| |
| * 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:: |
| |
| >>> from datetime import datetime, timezone |
| |
| >>> 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. |
| And :class:`~datetime.timedelta` objects can now divide one another. |
| |
| * The :meth:`datetime.date.strftime` method is no longer restricted to years |
| after 1900. The new supported year range is from 1000 to 9999 inclusive. |
| |
| * Whenever a two-digit year is used in a time tuple, the interpretation has been |
| governed by :attr:`time.accept2dyear`. The default is ``True`` which means that |
| for a two-digit year, the century is guessed according to the POSIX rules |
| governing the ``%y`` strptime format. |
| |
| Starting with Py3.2, use of the century guessing heuristic will emit a |
| :exc:`DeprecationWarning`. Instead, it is recommended that |
| :attr:`time.accept2dyear` be set to ``False`` so that large date ranges |
| can be used without guesswork:: |
| |
| >>> import time, warnings |
| >>> warnings.resetwarnings() # remove the default warning filters |
| |
| >>> time.accept2dyear = True # guess whether 11 means 11 or 2011 |
| >>> time.asctime((11, 1, 1, 12, 34, 56, 4, 1, 0)) |
| Warning (from warnings module): |
| ... |
| DeprecationWarning: Century info guessed for a 2-digit year. |
| 'Fri Jan 1 12:34:56 2011' |
| |
| >>> time.accept2dyear = False # use the full range of allowable dates |
| >>> time.asctime((11, 1, 1, 12, 34, 56, 4, 1, 0)) |
| 'Fri Jan 1 12:34:56 11' |
| |
| Several functions now have significantly expanded date ranges. When |
| :attr:`time.accept2dyear` is false, the :func:`time.asctime` function will |
| accept any year that fits in a C int, while the :func:`time.mktime` and |
| :func:`time.strftime` functions will accept the full range supported by the |
| corresponding operating system functions. |
| |
| (Contributed by Alexander Belopolsky and Victor Stinner in :issue:`1289118`, |
| :issue:`5094`, :issue:`6641`, :issue:`2706`, :issue:`1777412`, :issue:`8013`, |
| and :issue:`10827`.) |
| |
| .. XXX https://bugs.python.org/issue?%40search_text=datetime&%40sort=-activity |
| |
| math |
| ---- |
| |
| The :mod:`math` module has been updated with six new functions inspired by the |
| C99 standard. |
| |
| The :func:`~math.isfinite` function provides a reliable and fast way to detect |
| special values. It returns ``True`` for regular numbers and ``False`` for *Nan* or |
| *Infinity*: |
| |
| >>> from math import isfinite |
| >>> [isfinite(x) for x in (123, 4.56, float('Nan'), float('Inf'))] |
| [True, True, False, False] |
| |
| The :func:`~math.expm1` function computes ``e**x-1`` for small values of *x* |
| without incurring the loss of precision that usually accompanies the subtraction |
| of nearly equal quantities: |
| |
| >>> from math import expm1 |
| >>> expm1(0.013671875) # more accurate way to compute e**x-1 for a small x |
| 0.013765762467652909 |
| |
| The :func:`~math.erf` function computes a probability integral or `Gaussian |
| error function <https://en.wikipedia.org/wiki/Error_function>`_. The |
| complementary error function, :func:`~math.erfc`, is ``1 - erf(x)``: |
| |
| >>> from math import erf, erfc, sqrt |
| >>> erf(1.0/sqrt(2.0)) # portion of normal distribution within 1 standard deviation |
| 0.682689492137086 |
| >>> erfc(1.0/sqrt(2.0)) # portion of normal distribution outside 1 standard deviation |
| 0.31731050786291404 |
| >>> erf(1.0/sqrt(2.0)) + erfc(1.0/sqrt(2.0)) |
| 1.0 |
| |
| The :func:`~math.gamma` function is a continuous extension of the factorial |
| function. See https://en.wikipedia.org/wiki/Gamma_function for details. Because |
| the function is related to factorials, it grows large even for small values of |
| *x*, so there is also a :func:`~math.lgamma` function for computing the natural |
| logarithm of the gamma function: |
| |
| >>> from math import gamma, lgamma |
| >>> gamma(7.0) # six factorial |
| 720.0 |
| >>> lgamma(801.0) # log(800 factorial) |
| 4551.950730698041 |
| |
| (Contributed by Mark Dickinson.) |
| |
| abc |
| --- |
| |
| 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:: |
| |
| class Temperature(metaclass=abc.ABCMeta): |
| @abc.abstractclassmethod |
| def from_fahrenheit(cls, t): |
| ... |
| @abc.abstractclassmethod |
| def from_celsius(cls, t): |
| ... |
| |
| (Patch submitted by Daniel Urban; :issue:`5867`.) |
| |
| io |
| -- |
| |
| The :class:`io.BytesIO` has a new method, :meth:`~io.BytesIO.getbuffer`, which |
| provides functionality similar to :func:`memoryview`. It creates an editable |
| view of the data without making a copy. The buffer's random access and support |
| for slice notation are well-suited to in-place editing:: |
| |
| >>> REC_LEN, LOC_START, LOC_LEN = 34, 7, 11 |
| |
| >>> def change_location(buffer, record_number, location): |
| ... start = record_number * REC_LEN + LOC_START |
| ... buffer[start: start+LOC_LEN] = location |
| |
| >>> import io |
| |
| >>> byte_stream = io.BytesIO( |
| ... b'G3805 storeroom Main chassis ' |
| ... b'X7899 shipping Reserve cog ' |
| ... b'L6988 receiving Primary sprocket' |
| ... ) |
| >>> buffer = byte_stream.getbuffer() |
| >>> change_location(buffer, 1, b'warehouse ') |
| >>> change_location(buffer, 0, b'showroom ') |
| >>> print(byte_stream.getvalue()) |
| b'G3805 showroom Main chassis ' |
| b'X7899 warehouse Reserve cog ' |
| b'L6988 receiving Primary sprocket' |
| |
| (Contributed by Antoine Pitrou in :issue:`5506`.) |
| |
| reprlib |
| ------- |
| |
| When writing a :meth:`__repr__` method for a custom container, it is easy to |
| forget to handle the case where a member refers back to the container itself. |
| Python's builtin objects such as :class:`list` and :class:`set` handle |
| self-reference by displaying "..." in the recursive part of the representation |
| string. |
| |
| To help write such :meth:`__repr__` methods, the :mod:`reprlib` module has a new |
| decorator, :func:`~reprlib.recursive_repr`, for detecting recursive calls to |
| :meth:`__repr__` and substituting a placeholder string instead:: |
| |
| >>> class MyList(list): |
| ... @recursive_repr() |
| ... def __repr__(self): |
| ... return '<' + '|'.join(map(repr, self)) + '>' |
| ... |
| >>> m = MyList('abc') |
| >>> m.append(m) |
| >>> m.append('x') |
| >>> print(m) |
| <'a'|'b'|'c'|...|'x'> |
| |
| (Contributed by Raymond Hettinger in :issue:`9826` and :issue:`9840`.) |
| |
| logging |
| ------- |
| |
| In addition to dictionary-based configuration described above, the |
| :mod:`logging` package has many other improvements. |
| |
| The logging documentation has been augmented by a :ref:`basic tutorial |
| <logging-basic-tutorial>`\, an :ref:`advanced tutorial |
| <logging-advanced-tutorial>`\, and a :ref:`cookbook <logging-cookbook>` of |
| logging recipes. These documents are the fastest way to learn about logging. |
| |
| The :func:`logging.basicConfig` set-up function gained a *style* argument to |
| support three different types of string formatting. It defaults to "%" for |
| traditional %-formatting, can be set to "{" for the new :meth:`str.format` style, or |
| can be set to "$" for the shell-style formatting provided by |
| :class:`string.Template`. The following three configurations are equivalent:: |
| |
| >>> from logging import basicConfig |
| >>> basicConfig(style='%', format="%(name)s -> %(levelname)s: %(message)s") |
| >>> basicConfig(style='{', format="{name} -> {levelname} {message}") |
| >>> basicConfig(style='$', format="$name -> $levelname: $message") |
| |
| If no configuration is set-up before a logging event occurs, there is now a |
| default configuration using a :class:`~logging.StreamHandler` directed to |
| :attr:`sys.stderr` for events of ``WARNING`` level or higher. Formerly, an |
| event occurring before a configuration was set-up would either raise an |
| exception or silently drop the event depending on the value of |
| :attr:`logging.raiseExceptions`. The new default handler is stored in |
| :attr:`logging.lastResort`. |
| |
| The use of filters has been simplified. Instead of creating a |
| :class:`~logging.Filter` object, the predicate can be any Python callable that |
| returns ``True`` or ``False``. |
| |
| There were a number of other improvements that add flexibility and simplify |
| configuration. See the module documentation for a full listing of changes in |
| Python 3.2. |
| |
| csv |
| --- |
| |
| The :mod:`csv` module now supports a new dialect, :class:`~csv.unix_dialect`, |
| which applies quoting for all fields and a traditional Unix style with ``'\n'`` as |
| the line terminator. The registered dialect name is ``unix``. |
| |
| The :class:`csv.DictWriter` has a new method, |
| :meth:`~csv.DictWriter.writeheader` for writing-out an initial row to document |
| the field names:: |
| |
| >>> import csv, sys |
| >>> w = csv.DictWriter(sys.stdout, ['name', 'dept'], dialect='unix') |
| >>> w.writeheader() |
| "name","dept" |
| >>> w.writerows([ |
| ... {'name': 'tom', 'dept': 'accounting'}, |
| ... {'name': 'susan', 'dept': 'Salesl'}]) |
| "tom","accounting" |
| "susan","sales" |
| |
| (New dialect suggested by Jay Talbot in :issue:`5975`, and the new method |
| suggested by Ed Abraham in :issue:`1537721`.) |
| |
| contextlib |
| ---------- |
| |
| There is a new and slightly mind-blowing tool |
| :class:`~contextlib.ContextDecorator` that is helpful for creating a |
| :term:`context manager` that does double duty as a function decorator. |
| |
| As a convenience, this new functionality is used by |
| :func:`~contextlib.contextmanager` so that no extra effort is needed to support |
| both roles. |
| |
| The basic idea is that both context managers and function decorators can be used |
| for pre-action and post-action wrappers. Context managers wrap a group of |
| statements using a :keyword:`with` statement, and function decorators wrap a |
| group of statements enclosed in a function. So, occasionally there is a need to |
| write a pre-action or post-action wrapper that can be used in either role. |
| |
| For example, it is sometimes useful to wrap functions or groups of statements |
| with a logger that can track the time of entry and time of exit. Rather than |
| writing both a function decorator and a context manager for the task, the |
| :func:`~contextlib.contextmanager` provides both capabilities in a single |
| definition:: |
| |
| from contextlib import contextmanager |
| import logging |
| |
| logging.basicConfig(level=logging.INFO) |
| |
| @contextmanager |
| def track_entry_and_exit(name): |
| logging.info('Entering: {}'.format(name)) |
| yield |
| logging.info('Exiting: {}'.format(name)) |
| |
| Formerly, this would have only been usable as a context manager:: |
| |
| with track_entry_and_exit('widget loader'): |
| print('Some time consuming activity goes here') |
| load_widget() |
| |
| Now, it can be used as a decorator as well:: |
| |
| @track_entry_and_exit('widget loader') |
| def activity(): |
| print('Some time consuming activity goes here') |
| load_widget() |
| |
| Trying to fulfill two roles at once places some limitations on the technique. |
| Context managers normally have the flexibility to return an argument usable by |
| a :keyword:`with` statement, but there is no parallel for function decorators. |
| |
| In the above example, there is not a clean way for the *track_entry_and_exit* |
| context manager to return a logging instance for use in the body of enclosed |
| statements. |
| |
| (Contributed by Michael Foord in :issue:`9110`.) |
| |
| decimal and fractions |
| --------------------- |
| |
| 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 (:issue:`8188`):: |
| |
| assert hash(Fraction(3, 2)) == hash(1.5) == \ |
| hash(Decimal("1.5")) == hash(complex(1.5, 0)) |
| |
| Some of the hashing details are exposed through a new attribute, |
| :attr:`sys.hash_info`, which describes the bit width of the hash value, the |
| prime modulus, the hash values for *infinity* and *nan*, and the multiplier |
| used for the imaginary part of a number: |
| |
| >>> sys.hash_info # doctest: +SKIP |
| sys.hash_info(width=64, modulus=2305843009213693951, inf=314159, nan=0, imag=1000003) |
| |
| An early decision to limit the inter-operability of various numeric types has |
| been relaxed. It is still unsupported (and ill-advised) to have implicit |
| mixing in arithmetic expressions such as ``Decimal('1.1') + float('1.1')`` |
| because the latter loses information in the process of constructing the binary |
| float. However, since existing floating point value can be converted losslessly |
| to either a decimal or rational representation, it makes sense to add them to |
| the constructor and to support mixed-type comparisons. |
| |
| * The :class:`decimal.Decimal` constructor now accepts :class:`float` objects |
| directly so there in no longer a need to use the :meth:`~decimal.Decimal.from_float` |
| method (:issue:`8257`). |
| |
| * Mixed type comparisons are now fully supported so that |
| :class:`~decimal.Decimal` objects can be directly compared with :class:`float` |
| and :class:`fractions.Fraction` (:issue:`2531` and :issue:`8188`). |
| |
| Similar changes were made to :class:`fractions.Fraction` so that the |
| :meth:`~fractions.Fraction.from_float()` and :meth:`~fractions.Fraction.from_decimal` |
| methods are no longer needed (:issue:`8294`): |
| |
| >>> from decimal import Decimal |
| >>> from fractions import Fraction |
| >>> Decimal(1.1) |
| Decimal('1.100000000000000088817841970012523233890533447265625') |
| >>> Fraction(1.1) |
| Fraction(2476979795053773, 2251799813685248) |
| |
| Another useful change for the :mod:`decimal` module is that the |
| :attr:`Context.clamp` attribute is now public. This is useful in creating |
| contexts that correspond to the decimal interchange formats specified in IEEE |
| 754 (see :issue:`8540`). |
| |
| (Contributed by Mark Dickinson and Raymond Hettinger.) |
| |
| ftp |
| --- |
| |
| The :class:`ftplib.FTP` class now supports the context management 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`.) |
| |
| The :class:`~ftplib.FTP_TLS` 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:`8806`.) |
| |
| popen |
| ----- |
| |
| The :func:`os.popen` and :func:`subprocess.Popen` functions now support |
| :keyword:`with` statements for auto-closing of the file descriptors. |
| |
| (Contributed by Antoine Pitrou and Brian Curtin in :issue:`7461` and |
| :issue:`10554`.) |
| |
| select |
| ------ |
| |
| The :mod:`select` module now exposes a new, constant attribute, |
| :attr:`~select.PIPE_BUF`, which gives the minimum number of bytes which are |
| guaranteed not to block when :func:`select.select` says a pipe is ready |
| for writing. |
| |
| >>> import select |
| >>> select.PIPE_BUF |
| 512 |
| |
| (Available on Unix systems. Patch by Sébastien Sablé in :issue:`9862`) |
| |
| gzip and zipfile |
| ---------------- |
| |
| :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 as :class:`bytes` |
| before compressing and decompressing: |
| |
| >>> import gzip |
| >>> 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`.) |
| |
| Also, the :class:`zipfile.ZipExtFile` class was reworked internally to represent |
| files stored inside an archive. The new implementation is significantly faster |
| and can be wrapped in an :class:`io.BufferedReader` object for more speedups. It |
| also solves an issue where interleaved calls to *read* and *readline* gave the |
| wrong results. |
| |
| (Patch submitted by Nir Aides in :issue:`7610`.) |
| |
| tarfile |
| ------- |
| |
| The :class:`~tarfile.TarFile` class can now be used as a context manager. In |
| addition, its :meth:`~tarfile.TarFile.add` method has a new option, *filter*, |
| that controls which files are added to the archive and allows the file metadata |
| to be edited. |
| |
| The new *filter* option replaces the older, less flexible *exclude* parameter |
| which is now deprecated. If specified, the optional *filter* parameter needs to |
| be a :term:`keyword argument`. The user-supplied filter function accepts a |
| :class:`~tarfile.TarInfo` object and returns an updated |
| :class:`~tarfile.TarInfo` object, or if it wants the file to be excluded, the |
| function can return ``None``:: |
| |
| >>> import tarfile, glob |
| |
| >>> def myfilter(tarinfo): |
| ... if tarinfo.isfile(): # only save real files |
| ... tarinfo.uname = 'monty' # redact the user name |
| ... return tarinfo |
| |
| >>> with tarfile.open(name='myarchive.tar.gz', mode='w:gz') as tf: |
| ... for filename in glob.glob('*.txt'): |
| ... tf.add(filename, filter=myfilter) |
| ... tf.list() |
| -rw-r--r-- monty/501 902 2011-01-26 17:59:11 annotations.txt |
| -rw-r--r-- monty/501 123 2011-01-26 17:59:11 general_questions.txt |
| -rw-r--r-- monty/501 3514 2011-01-26 17:59:11 prion.txt |
| -rw-r--r-- monty/501 124 2011-01-26 17:59:11 py_todo.txt |
| -rw-r--r-- monty/501 1399 2011-01-26 17:59:11 semaphore_notes.txt |
| |
| (Proposed by Tarek Ziadé and implemented by Lars Gustäbel in :issue:`6856`.) |
| |
| hashlib |
| ------- |
| |
| The :mod:`hashlib` module has two new constant attributes listing the hashing |
| algorithms guaranteed to be present in all implementations and those available |
| on the current implementation:: |
| |
| >>> import hashlib |
| |
| >>> hashlib.algorithms_guaranteed |
| {'sha1', 'sha224', 'sha384', 'sha256', 'sha512', 'md5'} |
| |
| >>> hashlib.algorithms_available |
| {'md2', 'SHA256', 'SHA512', 'dsaWithSHA', 'mdc2', 'SHA224', 'MD4', 'sha256', |
| 'sha512', 'ripemd160', 'SHA1', 'MDC2', 'SHA', 'SHA384', 'MD2', |
| 'ecdsa-with-SHA1','md4', 'md5', 'sha1', 'DSA-SHA', 'sha224', |
| 'dsaEncryption', 'DSA', 'RIPEMD160', 'sha', 'MD5', 'sha384'} |
| |
| (Suggested by Carl Chenet in :issue:`7418`.) |
| |
| ast |
| --- |
| |
| The :mod:`ast` module has a wonderful a general-purpose tool for safely |
| evaluating expression strings using the Python literal |
| syntax. The :func:`ast.literal_eval` function serves as a secure alternative to |
| the builtin :func:`eval` function which is easily abused. Python 3.2 adds |
| :class:`bytes` and :class:`set` literals to the list of supported types: |
| strings, bytes, numbers, tuples, lists, dicts, sets, booleans, and ``None``. |
| |
| :: |
| |
| >>> from ast import literal_eval |
| |
| >>> request = "{'req': 3, 'func': 'pow', 'args': (2, 0.5)}" |
| >>> literal_eval(request) |
| {'args': (2, 0.5), 'req': 3, 'func': 'pow'} |
| |
| >>> request = "os.system('do something harmful')" |
| >>> literal_eval(request) |
| Traceback (most recent call last): |
| ... |
| ValueError: malformed node or string: <_ast.Call object at 0x101739a10> |
| |
| (Implemented by Benjamin Peterson and Georg Brandl.) |
| |
| os |
| -- |
| |
| Different operating systems use various encodings for filenames and environment |
| variables. The :mod:`os` module provides two new functions, |
| :func:`~os.fsencode` and :func:`~os.fsdecode`, for encoding and decoding |
| filenames: |
| |
| >>> import os |
| >>> filename = 'Sehenswürdigkeiten' |
| >>> os.fsencode(filename) |
| b'Sehensw\xc3\xbcrdigkeiten' |
| |
| Some operating systems allow direct access to encoded bytes in the |
| environment. If so, the :attr:`os.supports_bytes_environ` constant will be |
| true. |
| |
| For direct access to encoded environment variables (if available), |
| use the new :func:`os.getenvb` function or use :data:`os.environb` |
| which is a bytes version of :data:`os.environ`. |
| |
| (Contributed by Victor Stinner.) |
| |
| shutil |
| ------ |
| |
| The :func:`shutil.copytree` function has two new options: |
| |
| * *ignore_dangling_symlinks*: when ``symlinks=False`` so that the function |
| copies a file pointed to by a 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.) |
| |
| In addition, the :mod:`shutil` module now supports :ref:`archiving operations |
| <archiving-operations>` for zipfiles, uncompressed tarfiles, gzipped tarfiles, |
| and bzipped tarfiles. And there are functions for registering additional |
| archiving file formats (such as xz compressed tarfiles or custom formats). |
| |
| The principal functions are :func:`~shutil.make_archive` and |
| :func:`~shutil.unpack_archive`. By default, both operate on the current |
| directory (which can be set by :func:`os.chdir`) and on any sub-directories. |
| The archive filename needs to be specified with a full pathname. The archiving |
| step is non-destructive (the original files are left unchanged). |
| |
| :: |
| |
| >>> import shutil, pprint |
| |
| >>> os.chdir('mydata') # change to the source directory |
| >>> f = shutil.make_archive('/var/backup/mydata', |
| ... 'zip') # archive the current directory |
| >>> f # show the name of archive |
| '/var/backup/mydata.zip' |
| >>> os.chdir('tmp') # change to an unpacking |
| >>> shutil.unpack_archive('/var/backup/mydata.zip') # recover the data |
| |
| >>> pprint.pprint(shutil.get_archive_formats()) # display known formats |
| [('bztar', "bzip2'ed tar-file"), |
| ('gztar', "gzip'ed tar-file"), |
| ('tar', 'uncompressed tar file'), |
| ('zip', 'ZIP file')] |
| |
| >>> shutil.register_archive_format( # register a new archive format |
| ... name='xz', |
| ... function=xz.compress, # callable archiving function |
| ... extra_args=[('level', 8)], # arguments to the function |
| ... description='xz compression' |
| ... ) |
| |
| (Contributed by Tarek Ziadé.) |
| |
| sqlite3 |
| ------- |
| |
| The :mod:`sqlite3` module was updated to pysqlite version 2.6.0. It has two new capabilities. |
| |
| * The :attr:`sqlite3.Connection.in_transit` attribute is true if there is an |
| active transaction for uncommitted changes. |
| |
| * The :meth:`sqlite3.Connection.enable_load_extension` and |
| :meth:`sqlite3.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`.) |
| |
| html |
| ---- |
| |
| A new :mod:`html` module was introduced with only a single function, |
| :func:`~html.escape`, which is used for escaping reserved characters from HTML |
| markup: |
| |
| >>> import html |
| >>> html.escape('x > 2 && x < 7') |
| 'x > 2 && x < 7' |
| |
| socket |
| ------ |
| |
| The :mod:`socket` module has two new improvements. |
| |
| * 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`.) |
| |
| * :func:`socket.create_connection` now supports the context management protocol |
| to unconditionally consume :exc:`socket.error` exceptions and to close the |
| socket when done. |
| (Contributed by Giampaolo Rodolà; :issue:`9794`.) |
| |
| ssl |
| --- |
| |
| The :mod:`ssl` module added a number of features to satisfy common requirements |
| for secure (encrypted, authenticated) internet connections: |
| |
| * A new class, :class:`~ssl.SSLContext`, serves as a container for persistent |
| SSL data, such as protocol settings, certificates, private keys, and various |
| other options. It includes a :meth:`~ssl.SSLContext.wrap_socket` for creating |
| an SSL socket from an SSL context. |
| |
| * A new function, :func:`ssl.match_hostname`, supports server identity |
| verification for higher-level protocols by implementing the rules of HTTPS |
| (from :rfc:`2818`) which are also suitable for other protocols. |
| |
| * The :func:`ssl.wrap_socket` constructor function now takes a *ciphers* |
| argument. The *ciphers* string lists the allowed encryption algorithms using |
| the format described in the `OpenSSL documentation |
| <https://www.openssl.org/docs/apps/ciphers.html#CIPHER-LIST-FORMAT>`__. |
| |
| * When linked against recent versions of OpenSSL, the :mod:`ssl` module now |
| supports the Server Name Indication extension to the TLS protocol, allowing |
| multiple "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:`ssl.SSLContext.wrap_socket`. |
| |
| * Various options have been added to the :mod:`ssl` module, such as |
| :data:`~ssl.OP_NO_SSLv2` which disables the insecure and obsolete SSLv2 |
| protocol. |
| |
| * The extension now loads all the OpenSSL ciphers and digest algorithms. If |
| some SSL certificates cannot be verified, they are reported as an "unknown |
| algorithm" error. |
| |
| * The version of OpenSSL being used is now accessible using 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). |
| |
| (Contributed by Antoine Pitrou in :issue:`8850`, :issue:`1589`, :issue:`8322`, |
| :issue:`5639`, :issue:`4870`, :issue:`8484`, and :issue:`8321`.) |
| |
| nntp |
| ---- |
| |
| The :mod:`nntplib` module has a revamped implementation with better bytes and |
| text 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. |
| |
| Support for secure connections through both implicit (using |
| :class:`nntplib.NNTP_SSL`) and explicit (using :meth:`nntplib.NNTP.starttls`) |
| TLS has also been added. |
| |
| (Contributed by Antoine Pitrou in :issue:`9360` and Andrew Vant in :issue:`1926`.) |
| |
| certificates |
| ------------ |
| |
| :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`.) |
| |
| imaplib |
| ------- |
| |
| Support for explicit TLS on standard IMAP4 connections has been added through |
| the new :mod:`imaplib.IMAP4.starttls` method. |
| |
| (Contributed by Lorenzo M. Catucci and Antoine Pitrou, :issue:`4471`.) |
| |
| http.client |
| ----------- |
| |
| There were a number of small API improvements in the :mod:`http.client` module. |
| The old-style HTTP 0.9 simple responses are no longer supported and the *strict* |
| parameter is deprecated in all classes. |
| |
| The :class:`~http.client.HTTPConnection` and |
| :class:`~http.client.HTTPSConnection` classes now have a *source_address* |
| parameter for a (host, port) tuple indicating where the HTTP connection is made |
| from. |
| |
| Support for certificate checking and HTTPS virtual hosts were added to |
| :class:`~http.client.HTTPSConnection`. |
| |
| The :meth:`~http.client.HTTPConnection.request` method on connection objects |
| allowed an optional *body* argument so that a :term:`file object` could be used |
| to supply the content of the request. Conveniently, the *body* argument now |
| also accepts an :term:`iterable` object so long as it includes an explicit |
| ``Content-Length`` header. This extended interface is much more flexible than |
| before. |
| |
| To establish an HTTPS connection through a proxy server, there is a new |
| :meth:`~http.client.HTTPConnection.set_tunnel` method that sets the host and |
| port for HTTP Connect tunneling. |
| |
| To match the behavior of :mod:`http.server`, the HTTP client library now also |
| encodes headers with ISO-8859-1 (Latin-1) encoding. It was already doing that |
| for incoming headers, so now the behavior is consistent for both incoming and |
| outgoing traffic. (See work by Armin Ronacher in :issue:`10980`.) |
| |
| unittest |
| -------- |
| |
| The unittest module has a number of improvements supporting test discovery for |
| packages, easier experimentation at the interactive prompt, new testcase |
| methods, improved diagnostic messages for test failures, and better method |
| names. |
| |
| * 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``: |
| |
| .. code-block:: shell-session |
| |
| $ python -m unittest discover -s my_proj_dir -p _test.py |
| |
| (Contributed by Michael Foord.) |
| |
| * Experimentation at the interactive prompt is now easier because the |
| :class:`unittest.case.TestCase` class can now be instantiated without |
| arguments: |
| |
| >>> from unittest import TestCase |
| >>> TestCase().assertEqual(pow(2, 3), 8) |
| |
| (Contributed by Michael Foord.) |
| |
| * The :mod:`unittest` module has two new methods, |
| :meth:`~unittest.TestCase.assertWarns` and |
| :meth:`~unittest.TestCase.assertWarnsRegex` to verify that a given warning type |
| is triggered by the code under test:: |
| |
| with self.assertWarns(DeprecationWarning): |
| legacy_function('XYZ') |
| |
| (Contributed by Antoine Pitrou, :issue:`9754`.) |
| |
| Another new method, :meth:`~unittest.TestCase.assertCountEqual` is used to |
| compare two iterables to determine if their element counts are equal (whether |
| the same elements are present with the same number of occurrences regardless |
| of order):: |
| |
| def test_anagram(self): |
| self.assertCountEqual('algorithm', 'logarithm') |
| |
| (Contributed by Raymond Hettinger.) |
| |
| * 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 that sets maximum length of |
| diffs displayed. |
| |
| * In addition, the method names in the module have 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. |
| |
| (Contributed by Raymond Hettinger and implemented by Ezio Melotti.) |
| |
| * To improve consistency, some long-standing method aliases are being |
| deprecated in favor of the preferred names: |
| |
| =============================== ============================== |
| Old Name Preferred Name |
| =============================== ============================== |
| :meth:`assert_` :meth:`.assertTrue` |
| :meth:`assertEquals` :meth:`.assertEqual` |
| :meth:`assertNotEquals` :meth:`.assertNotEqual` |
| :meth:`assertAlmostEquals` :meth:`.assertAlmostEqual` |
| :meth:`assertNotAlmostEquals` :meth:`.assertNotAlmostEqual` |
| =============================== ============================== |
| |
| Likewise, the ``TestCase.fail*`` methods deprecated in Python 3.1 are expected |
| to be removed in Python 3.3. Also see the :ref:`deprecated-aliases` section in |
| the :mod:`unittest` documentation. |
| |
| (Contributed by Ezio Melotti; :issue:`9424`.) |
| |
| * The :meth:`~unittest.TestCase.assertDictContainsSubset` method was deprecated |
| because it was misimplemented with the arguments in the wrong order. This |
| created hard-to-debug optical illusions where tests like |
| ``TestCase().assertDictContainsSubset({'a':1, 'b':2}, {'a':1})`` would fail. |
| |
| (Contributed by Raymond Hettinger.) |
| |
| random |
| ------ |
| |
| The integer methods in the :mod:`random` module now do a better job of producing |
| uniform distributions. Previously, they computed selections with |
| ``int(n*random())`` which had a slight bias whenever *n* was not a power of two. |
| Now, multiple selections are made from a range up to the next power of two and a |
| selection is kept only when it falls within the range ``0 <= x < n``. The |
| functions and methods affected are :func:`~random.randrange`, |
| :func:`~random.randint`, :func:`~random.choice`, :func:`~random.shuffle` and |
| :func:`~random.sample`. |
| |
| (Contributed by Raymond Hettinger; :issue:`9025`.) |
| |
| poplib |
| ------ |
| |
| :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`.) |
| |
| asyncore |
| -------- |
| |
| :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`.) |
| |
| tempfile |
| -------- |
| |
| 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 dir:', tmpdirname) |
| |
| (Contributed by Neil Schemenauer and Nick Coghlan; :issue:`5178`.) |
| |
| inspect |
| ------- |
| |
| * The :mod:`inspect` module has a new function |
| :func:`~inspect.getgeneratorstate` to easily identify the current state of a |
| generator-iterator:: |
| |
| >>> from inspect import getgeneratorstate |
| >>> def gen(): |
| ... yield 'demo' |
| >>> g = gen() |
| >>> getgeneratorstate(g) |
| 'GEN_CREATED' |
| >>> next(g) |
| 'demo' |
| >>> getgeneratorstate(g) |
| 'GEN_SUSPENDED' |
| >>> next(g, None) |
| >>> getgeneratorstate(g) |
| 'GEN_CLOSED' |
| |
| (Contributed by Rodolpho Eckhardt and Nick Coghlan, :issue:`10220`.) |
| |
| * To support lookups without the possibility of activating a dynamic attribute, |
| the :mod:`inspect` module has a new function, :func:`~inspect.getattr_static`. |
| Unlike :func:`hasattr`, this is a true read-only search, guaranteed not to |
| change state while it is searching:: |
| |
| >>> class A: |
| ... @property |
| ... def f(self): |
| ... print('Running') |
| ... return 10 |
| ... |
| >>> a = A() |
| >>> getattr(a, 'f') |
| Running |
| 10 |
| >>> inspect.getattr_static(a, 'f') |
| <property object at 0x1022bd788> |
| |
| (Contributed by Michael Foord.) |
| |
| pydoc |
| ----- |
| |
| The :mod:`pydoc` module now provides a much-improved Web server interface, as |
| well as a new command-line option ``-b`` to automatically open a browser window |
| to display that server: |
| |
| .. code-block:: shell-session |
| |
| $ pydoc3.2 -b |
| |
| (Contributed by Ron Adam; :issue:`2001`.) |
| |
| dis |
| --- |
| |
| The :mod:`dis` module gained two new functions for inspecting code, |
| :func:`~dis.code_info` and :func:`~dis.show_code`. Both provide detailed code |
| object information for the supplied function, method, source code string or code |
| object. The former returns a string and the latter prints it:: |
| |
| >>> import dis, random |
| >>> dis.show_code(random.choice) |
| Name: choice |
| Filename: /Library/Frameworks/Python.framework/Versions/3.2/lib/python3.2/random.py |
| Argument count: 2 |
| Kw-only arguments: 0 |
| Number of locals: 3 |
| Stack size: 11 |
| Flags: OPTIMIZED, NEWLOCALS, NOFREE |
| Constants: |
| 0: 'Choose a random element from a non-empty sequence.' |
| 1: 'Cannot choose from an empty sequence' |
| Names: |
| 0: _randbelow |
| 1: len |
| 2: ValueError |
| 3: IndexError |
| Variable names: |
| 0: self |
| 1: seq |
| 2: i |
| |
| In addition, the :func:`~dis.dis` function now accepts string arguments |
| so that the common idiom ``dis(compile(s, '', 'eval'))`` can be shortened |
| to ``dis(s)``:: |
| |
| >>> dis('3*x+1 if x%2==1 else x//2') |
| 1 0 LOAD_NAME 0 (x) |
| 3 LOAD_CONST 0 (2) |
| 6 BINARY_MODULO |
| 7 LOAD_CONST 1 (1) |
| 10 COMPARE_OP 2 (==) |
| 13 POP_JUMP_IF_FALSE 28 |
| 16 LOAD_CONST 2 (3) |
| 19 LOAD_NAME 0 (x) |
| 22 BINARY_MULTIPLY |
| 23 LOAD_CONST 1 (1) |
| 26 BINARY_ADD |
| 27 RETURN_VALUE |
| >> 28 LOAD_NAME 0 (x) |
| 31 LOAD_CONST 0 (2) |
| 34 BINARY_FLOOR_DIVIDE |
| 35 RETURN_VALUE |
| |
| Taken together, these improvements make it easier to explore how CPython is |
| implemented and to see for yourself what the language syntax does |
| under-the-hood. |
| |
| (Contributed by Nick Coghlan in :issue:`9147`.) |
| |
| dbm |
| --- |
| |
| All database modules now support the :meth:`get` and :meth:`setdefault` methods. |
| |
| (Suggested by Ray Allen in :issue:`9523`.) |
| |
| ctypes |
| ------ |
| |
| A new type, :class:`ctypes.c_ssize_t` represents the C :c:type:`ssize_t` datatype. |
| |
| site |
| ---- |
| |
| The :mod:`site` module has three new functions useful for reporting on the |
| details of a given Python installation. |
| |
| * :func:`~site.getsitepackages` lists all global site-packages directories. |
| |
| * :func:`~site.getuserbase` reports on the user's base directory where data can |
| be stored. |
| |
| * :func:`~site.getusersitepackages` reveals the user-specific site-packages |
| directory path. |
| |
| :: |
| |
| >>> import site |
| >>> site.getsitepackages() |
| ['/Library/Frameworks/Python.framework/Versions/3.2/lib/python3.2/site-packages', |
| '/Library/Frameworks/Python.framework/Versions/3.2/lib/site-python', |
| '/Library/Python/3.2/site-packages'] |
| >>> site.getuserbase() |
| '/Users/raymondhettinger/Library/Python/3.2' |
| >>> site.getusersitepackages() |
| '/Users/raymondhettinger/Library/Python/3.2/lib/python/site-packages' |
| |
| Conveniently, some of site's functionality is accessible directly from the |
| command-line: |
| |
| .. code-block:: shell-session |
| |
| $ python -m site --user-base |
| /Users/raymondhettinger/.local |
| $ python -m site --user-site |
| /Users/raymondhettinger/.local/lib/python3.2/site-packages |
| |
| (Contributed by Tarek Ziadé in :issue:`6693`.) |
| |
| sysconfig |
| --------- |
| |
| The new :mod:`sysconfig` module makes it straightforward to discover |
| installation paths and configuration variables that vary across platforms and |
| installations. |
| |
| 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 |
| such as "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: |
| |
| .. code-block:: doscon |
| |
| 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" |
| |
| (Moved out of Distutils by Tarek Ziadé.) |
| |
| pdb |
| --- |
| |
| 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. |
| |
| (Contributed by Georg Brandl, Antonio Cuni and Ilya Sandler.) |
| |
| configparser |
| ------------ |
| |
| The :mod:`configparser` module was modified to improve usability and |
| predictability of the default parser and its supported INI syntax. The old |
| :class:`ConfigParser` class was removed in favor of :class:`SafeConfigParser` |
| which has in turn been renamed to :class:`~configparser.ConfigParser`. Support |
| for inline comments is now turned off by default and section or option |
| duplicates are not allowed in a single configuration source. |
| |
| Config parsers gained a new API based on the mapping protocol:: |
| |
| >>> parser = ConfigParser() |
| >>> parser.read_string(""" |
| ... [DEFAULT] |
| ... location = upper left |
| ... visible = yes |
| ... editable = no |
| ... color = blue |
| ... |
| ... [main] |
| ... title = Main Menu |
| ... color = green |
| ... |
| ... [options] |
| ... title = Options |
| ... """) |
| >>> parser['main']['color'] |
| 'green' |
| >>> parser['main']['editable'] |
| 'no' |
| >>> section = parser['options'] |
| >>> section['title'] |
| 'Options' |
| >>> section['title'] = 'Options (editable: %(editable)s)' |
| >>> section['title'] |
| 'Options (editable: no)' |
| |
| The new API is implemented on top of the classical API, so custom parser |
| subclasses should be able to use it without modifications. |
| |
| The INI file structure accepted by config parsers can now be customized. Users |
| can specify alternative option/value delimiters and comment prefixes, change the |
| name of the *DEFAULT* section or switch the interpolation syntax. |
| |
| There is support for pluggable interpolation including an additional interpolation |
| handler :class:`~configparser.ExtendedInterpolation`:: |
| |
| >>> parser = ConfigParser(interpolation=ExtendedInterpolation()) |
| >>> parser.read_dict({'buildout': {'directory': '/home/ambv/zope9'}, |
| ... 'custom': {'prefix': '/usr/local'}}) |
| >>> parser.read_string(""" |
| ... [buildout] |
| ... parts = |
| ... zope9 |
| ... instance |
| ... find-links = |
| ... ${buildout:directory}/downloads/dist |
| ... |
| ... [zope9] |
| ... recipe = plone.recipe.zope9install |
| ... location = /opt/zope |
| ... |
| ... [instance] |
| ... recipe = plone.recipe.zope9instance |
| ... zope9-location = ${zope9:location} |
| ... zope-conf = ${custom:prefix}/etc/zope.conf |
| ... """) |
| >>> parser['buildout']['find-links'] |
| '\n/home/ambv/zope9/downloads/dist' |
| >>> parser['instance']['zope-conf'] |
| '/usr/local/etc/zope.conf' |
| >>> instance = parser['instance'] |
| >>> instance['zope-conf'] |
| '/usr/local/etc/zope.conf' |
| >>> instance['zope9-location'] |
| '/opt/zope' |
| |
| A number of smaller features were also introduced, like support for specifying |
| encoding in read operations, specifying fallback values for get-functions, or |
| reading directly from dictionaries and strings. |
| |
| (All changes contributed by Łukasz Langa.) |
| |
| .. XXX consider showing a difflib example |
| |
| urllib.parse |
| ------------ |
| |
| A number of usability improvements were made for the :mod:`urllib.parse` module. |
| |
| The :func:`~urllib.parse.urlparse` function now supports `IPv6 |
| <https://en.wikipedia.org/wiki/IPv6>`_ addresses as described in :rfc:`2732`: |
| |
| >>> import urllib.parse |
| >>> urllib.parse.urlparse('http://[dead:beef:cafe:5417:affe:8FA3:deaf:feed]/foo/') # doctest: +NORMALIZE_WHITESPACE |
| ParseResult(scheme='http', |
| netloc='[dead:beef:cafe:5417:affe:8FA3:deaf:feed]', |
| path='/foo/', |
| params='', |
| query='', |
| fragment='') |
| |
| The :func:`~urllib.parse.urldefrag` function now returns a :term:`named tuple`:: |
| |
| >>> r = urllib.parse.urldefrag('http://python.org/about/#target') |
| >>> r |
| DefragResult(url='http://python.org/about/', fragment='target') |
| >>> r[0] |
| 'http://python.org/about/' |
| >>> r.fragment |
| 'target' |
| |
| And, the :func:`~urllib.parse.urlencode` function is now much more flexible, |
| accepting either a string or bytes type for the *query* argument. If it is a |
| string, then the *safe*, *encoding*, and *error* parameters are sent to |
| :func:`~urllib.parse.quote_plus` for encoding:: |
| |
| >>> urllib.parse.urlencode([ |
| ... ('type', 'telenovela'), |
| ... ('name', '¿Dónde Está Elisa?')], |
| ... encoding='latin-1') |
| 'type=telenovela&name=%BFD%F3nde+Est%E1+Elisa%3F' |
| |
| As detailed in :ref:`parsing-ascii-encoded-bytes`, all the :mod:`urllib.parse` |
| functions now accept ASCII-encoded byte strings as input, so long as they are |
| not mixed with regular strings. If ASCII-encoded byte strings are given as |
| parameters, the return types will also be an ASCII-encoded byte strings: |
| |
| >>> urllib.parse.urlparse(b'http://www.python.org:80/about/') # doctest: +NORMALIZE_WHITESPACE |
| ParseResultBytes(scheme=b'http', netloc=b'www.python.org:80', |
| path=b'/about/', params=b'', query=b'', fragment=b'') |
| |
| (Work by Nick Coghlan, Dan Mahn, and Senthil Kumaran in :issue:`2987`, |
| :issue:`5468`, and :issue:`9873`.) |
| |
| mailbox |
| ------- |
| |
| Thanks to a concerted effort by R. David Murray, the :mod:`mailbox` module has |
| been fixed for Python 3.2. The challenge was that mailbox had been originally |
| designed with a text interface, but email messages are best represented with |
| :class:`bytes` because various parts of a message may have different encodings. |
| |
| The solution harnessed the :mod:`email` package's binary support for parsing |
| arbitrary email messages. In addition, the solution required a number of API |
| changes. |
| |
| As expected, the :meth:`~mailbox.Mailbox.add` method for |
| :class:`mailbox.Mailbox` objects now accepts binary input. |
| |
| :class:`~io.StringIO` and text file input are deprecated. Also, string input |
| will fail early if non-ASCII characters are used. Previously it would fail when |
| the email was processed in a later step. |
| |
| There is also support for binary output. The :meth:`~mailbox.Mailbox.get_file` |
| method now returns a file in the binary mode (where it used to incorrectly set |
| the file to text-mode). There is also a new :meth:`~mailbox.Mailbox.get_bytes` |
| method that returns a :class:`bytes` representation of a message corresponding |
| to a given *key*. |
| |
| It is still possible to get non-binary output using the old API's |
| :meth:`~mailbox.Mailbox.get_string` method, but that approach |
| is not very useful. Instead, it is best to extract messages from |
| a :class:`~mailbox.Message` object or to load them from binary input. |
| |
| (Contributed by R. David Murray, with efforts from Steffen Daode Nurpmeso and an |
| initial patch by Victor Stinner in :issue:`9124`.) |
| |
| turtledemo |
| ---------- |
| |
| The demonstration code for the :mod:`turtle` module was moved from the *Demo* |
| directory to main library. It includes over a dozen sample scripts with |
| lively displays. Being on :attr:`sys.path`, it can now be run directly |
| from the command-line: |
| |
| .. code-block:: shell-session |
| |
| $ python -m turtledemo |
| |
| (Moved from the Demo directory by Alexander Belopolsky in :issue:`10199`.) |
| |
| Multi-threading |
| =============== |
| |
| * The mechanism for serializing execution of concurrently running Python threads |
| (generally known as the :term:`GIL` or :term:`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 |
| <https://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:`~threading.Lock.acquire` method. (Contributed by Antoine Pitrou; |
| :issue:`7316`.) |
| |
| * Similarly, :meth:`threading.Semaphore.acquire` also gained a *timeout* |
| argument. (Contributed by Torsten Landschoff; :issue:`850728`.) |
| |
| * Regular and recursive lock acquisitions can now be interrupted by signals on |
| platforms using Pthreads. This means that Python programs that deadlock while |
| acquiring locks can be successfully killed by repeatedly sending SIGINT to the |
| process (by pressing :kbd:`Ctrl+C` in most shells). |
| (Contributed by Reid Kleckner; :issue:`8844`.) |
| |
| |
| 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 contributed 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 <https://en.wikipedia.org/wiki/Timsort>`_ used in |
| :meth:`list.sort` and :func:`sorted` now runs faster and uses 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, two arrays of keys and values are |
| sorted in parallel. This saves the memory consumed by the sort wrappers, |
| and it saves time lost to delegating comparisons. |
| |
| (Patch by Daniel Stutzbach 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`.) |
| |
| |
| * Integer to string conversions now work two "digits" at a time, reducing the |
| number of division and modulo operations. |
| |
| (:issue:`6713` by Gawain Bolton, Mark Dickinson, and Victor Stinner.) |
| |
| 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 |
| :func:`operator.attrgetter` function has been sped-up (: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 |
| <http://unicode.org/versions/Unicode6.0.0/>`_. The update to the standard adds |
| over 2,000 new characters including `emoji <https://en.wikipedia.org/wiki/Emoji>`_ |
| symbols which are important for mobile phones. |
| |
| In addition, the updated standard has altered the character properties for two |
| Kannada characters (U+0CF1, U+0CF2) and one New Tai Lue numeric character |
| (U+19DA), making the former eligible for use in identifiers while disqualifying |
| the latter. For more information, see `Unicode Character Database Changes |
| <http://www.unicode.org/versions/Unicode6.0.0/#Database_Changes>`_. |
| |
| |
| Codecs |
| ====== |
| |
| Support was added for *cp720* Arabic DOS encoding (:issue:`1616979`). |
| |
| MBCS encoding no longer ignores the error handler argument. In the default |
| strict mode, it raises an :exc:`UnicodeDecodeError` when it encounters an |
| undecodable byte sequence and an :exc:`UnicodeEncodeError` for an unencodable |
| character. |
| |
| The MBCS codec supports ``'strict'`` and ``'ignore'`` error handlers for |
| decoding, and ``'strict'`` and ``'replace'`` for encoding. |
| |
| To emulate Python3.1 MBCS encoding, select the ``'ignore'`` handler for decoding |
| and the ``'replace'`` handler for encoding. |
| |
| On Mac OS X, Python decodes command line arguments with ``'utf-8'`` rather than |
| the locale encoding. |
| |
| By default, :mod:`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 a helpful adjunct to the |
| documentation, so now many modules now 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 code** :source:`Lib/functools.py`. |
| |
| (Contributed by Raymond Hettinger; see |
| `rationale <https://rhettinger.wordpress.com/2011/01/28/open-your-source-more/>`_.) |
| |
| * 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 in :issue:`9528`.) |
| |
| * The unmaintained :file:`Demo` directory has been removed. Some demos were |
| integrated into the documentation, some were moved to the :file:`Tools/demo` |
| directory, and others were removed altogether. |
| |
| (Contributed by Georg Brandl in :issue:`7962`.) |
| |
| |
| IDLE |
| ==== |
| |
| * The format menu now has an option to clean source files by stripping |
| trailing whitespace. |
| |
| (Contributed by Raymond Hettinger; :issue:`5150`.) |
| |
| * IDLE on Mac OS X now works with both Carbon AquaTk and Cocoa AquaTk. |
| |
| (Contributed by Kevin Walzer, Ned Deily, and Ronald Oussoren; :issue:`6075`.) |
| |
| Code Repository |
| =============== |
| |
| In addition to the existing Subversion code repository at http://svn.python.org |
| there is now a `Mercurial <https://www.mercurial-scm.org/>`_ repository at |
| https://hg.python.org/\ . |
| |
| After the 3.2 release, there are plans to switch to Mercurial as the primary |
| repository. This distributed version control system should make it easier for |
| members of the community to create and share external changesets. See |
| :pep:`385` for details. |
| |
| To learn to use the new version control system, see the `tutorial by Joel |
| Spolsky <http://hginit.com>`_ or the `Guide to Mercurial Workflows |
| <https://www.mercurial-scm.org/guide>`_. |
| |
| |
| Build and C API Changes |
| ======================= |
| |
| Changes to Python's build process and to the C API include: |
| |
| * The *idle*, *pydoc* and *2to3* scripts are now installed with a |
| version-specific suffix on ``make altinstall`` (:issue:`10679`). |
| |
| * 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, :c: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). |
| |
| (Suggested by Raymond Hettinger and implemented by Benjamin Peterson; |
| :issue:`9778`.) |
| |
| * A new macro :c:macro:`Py_VA_COPY` copies the state of the variable argument |
| list. It is equivalent to C99 *va_copy* but available on all Python platforms |
| (:issue:`2443`). |
| |
| * A new C API function :c:func:`PySys_SetArgvEx` allows an embedded interpreter |
| to set :attr:`sys.argv` without also modifying :attr:`sys.path` |
| (:issue:`5753`). |
| |
| * :c:macro:`PyEval_CallObject` is now only available in macro form. The |
| function declaration, which was kept for backwards compatibility reasons, is |
| now removed -- the macro was introduced in 1997 (:issue:`8276`). |
| |
| * There is a new function :c:func:`PyLong_AsLongLongAndOverflow` which |
| is analogous to :c:func:`PyLong_AsLongAndOverflow`. They both serve to |
| convert Python :class:`int` into a native fixed-width type while providing |
| detection of cases where the conversion won't fit (:issue:`7767`). |
| |
| * The :c:func:`PyUnicode_CompareWithASCIIString` function now returns *not |
| equal* if the Python string is *NUL* terminated. |
| |
| * There is a new function :c:func:`PyErr_NewExceptionWithDoc` that is |
| like :c:func:`PyErr_NewException` but allows a docstring to be specified. |
| This lets C exceptions have the same self-documenting capabilities as |
| their pure Python counterparts (:issue:`7033`). |
| |
| * When compiled with the ``--with-valgrind`` option, the pymalloc |
| allocator will be automatically disabled when running under Valgrind. This |
| gives improved memory leak detection when running under Valgrind, while taking |
| advantage of pymalloc at other times (:issue:`2422`). |
| |
| * Removed the ``O?`` format from the *PyArg_Parse* functions. The format is no |
| longer used and it had never been documented (:issue:`8837`). |
| |
| There were a number of other small changes to the C-API. See the |
| :source:`Misc/NEWS` file for a complete list. |
| |
| Also, there were a number of updates to the Mac OS X build, see |
| :source:`Mac/BuildScript/README.txt` for details. For users running a 32/64-bit |
| build, there is a known problem with the default Tcl/Tk on Mac OS X 10.6. |
| Accordingly, we recommend installing an updated alternative such as |
| `ActiveState Tcl/Tk 8.5.9 <https://www.activestate.com/activetcl/downloads>`_\. |
| See https://www.python.org/download/mac/tcltk/ for additional details. |
| |
| Porting to Python 3.2 |
| ===================== |
| |
| This section lists previously described changes and other bugfixes that may |
| require changes to your code: |
| |
| * The :mod:`configparser` module has a number of clean-ups. The major change is |
| to replace the old :class:`ConfigParser` class with long-standing preferred |
| alternative :class:`SafeConfigParser`. In addition there are a number of |
| smaller incompatibilities: |
| |
| * The interpolation syntax is now validated on |
| :meth:`~configparser.ConfigParser.get` and |
| :meth:`~configparser.ConfigParser.set` operations. In the default |
| interpolation scheme, only two tokens with percent signs are valid: ``%(name)s`` |
| and ``%%``, the latter being an escaped percent sign. |
| |
| * The :meth:`~configparser.ConfigParser.set` and |
| :meth:`~configparser.ConfigParser.add_section` methods now verify that |
| values are actual strings. Formerly, unsupported types could be introduced |
| unintentionally. |
| |
| * Duplicate sections or options from a single source now raise either |
| :exc:`~configparser.DuplicateSectionError` or |
| :exc:`~configparser.DuplicateOptionError`. Formerly, duplicates would |
| silently overwrite a previous entry. |
| |
| * Inline comments are now disabled by default so now the **;** character |
| can be safely used in values. |
| |
| * Comments now can be indented. Consequently, for **;** or **#** to appear at |
| the start of a line in multiline values, it has to be interpolated. This |
| keeps comment prefix characters in values from being mistaken as comments. |
| |
| * ``""`` is now a valid value and is no longer automatically converted to an |
| empty string. For empty strings, use ``"option ="`` in a line. |
| |
| * 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`. |
| |
| * The :meth:`array.tostring` and :meth:`array.fromstring` have been renamed to |
| :meth:`array.tobytes` and :meth:`array.frombytes` for clarity. The old names |
| have been deprecated. (See :issue:`8990`.) |
| |
| * ``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 salt string seeds with an |
| sha512 hash function. 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 <https://codereview.appspot.com/53094>`_.) |
| |
| * :func:`struct.pack` now only allows bytes for the ``s`` string pack code. |
| Formerly, it would accept text arguments and implicitly encode them to bytes |
| using UTF-8. This was problematic because it made assumptions about the |
| correct encoding and because a variable-length encoding can fail when writing |
| to fixed length segment of a structure. |
| |
| Code such as ``struct.pack('<6sHHBBB', 'GIF87a', x, y)`` should be rewritten |
| with to use bytes instead of text, ``struct.pack('<6sHHBBB', b'GIF87a', x, y)``. |
| |
| (Discovered by David Beazley and fixed by Victor Stinner; :issue:`10783`.) |
| |
| * The :class:`xml.etree.ElementTree` class now raises an |
| :exc:`xml.etree.ElementTree.ParseError` when a parse fails. Previously it |
| raised an :exc:`xml.parsers.expat.ExpatError`. |
| |
| * The new, longer :func:`str` value on floats may break doctests which rely on |
| the old output format. |
| |
| * In :class:`subprocess.Popen`, the default value for *close_fds* is now |
| ``True`` under Unix; under Windows, it is ``True`` if the three standard |
| streams are set to ``None``, ``False`` otherwise. Previously, *close_fds* |
| was always ``False`` by default, which produced difficult to solve bugs |
| or race conditions when open file descriptors would leak into the child |
| process. |
| |
| * Support for legacy HTTP 0.9 has been removed from :mod:`urllib.request` |
| and :mod:`http.client`. Such support is still present on the server side |
| (in :mod:`http.server`). |
| |
| (Contributed by Antoine Pitrou, :issue:`10711`.) |
| |
| * SSL sockets in timeout mode now raise :exc:`socket.timeout` when a timeout |
| occurs, rather than a generic :exc:`~ssl.SSLError`. |
| |
| (Contributed by Antoine Pitrou, :issue:`10272`.) |
| |
| * The misleading functions :c:func:`PyEval_AcquireLock()` and |
| :c:func:`PyEval_ReleaseLock()` have been officially deprecated. The |
| thread-state aware APIs (such as :c:func:`PyEval_SaveThread()` |
| and :c:func:`PyEval_RestoreThread()`) should be used instead. |
| |
| * Due to security risks, :func:`asyncore.handle_accept` has been deprecated, and |
| a new function, :func:`asyncore.handle_accepted`, was added to replace it. |
| |
| (Contributed by Giampaolo Rodola in :issue:`6706`.) |
| |
| * Due to the new :term:`GIL` implementation, :c:func:`PyEval_InitThreads()` |
| cannot be called before :c:func:`Py_Initialize()` anymore. |