| **************************** |
| What's New in Python 2.7 |
| **************************** |
| |
| :Author: A.M. Kuchling (amk at amk.ca) |
| :Release: |release| |
| :Date: |today| |
| |
| .. hyperlink all the methods & functions. |
| |
| .. T_STRING_INPLACE not described in main docs |
| .. "Format String Syntax" in string.rst could use many more examples. |
| |
| .. $Id$ |
| Rules for maintenance: |
| |
| * Anyone can add text to this document. Do not spend very much time |
| on the wording of your changes, because your text will probably |
| get rewritten to some degree. |
| |
| * The maintainer will go through Misc/NEWS periodically and add |
| changes; it's therefore more important to add your changes to |
| Misc/NEWS than to this file. |
| |
| * This is not a complete list of every single change; completeness |
| is the purpose of Misc/NEWS. Some changes I consider too small |
| or esoteric to include. If such a change is added to the text, |
| I'll just remove it. (This is another reason you shouldn't spend |
| too much time on writing your addition.) |
| |
| * If you want to draw your new text to the attention of the |
| maintainer, add 'XXX' to the beginning of the paragraph or |
| section. |
| |
| * It's OK to just add a fragmentary note about a change. For |
| example: "XXX Describe the transmogrify() function added to the |
| socket module." The maintainer will research the change and |
| write the necessary text. |
| |
| * You can comment out your additions if you like, but it's not |
| necessary (especially when a final release is some months away). |
| |
| * Credit the author of a patch or bugfix. Just the name is |
| sufficient; the e-mail address isn't necessary. |
| |
| * It's helpful to add the bug/patch number in a parenthetical comment. |
| |
| XXX Describe the transmogrify() function added to the socket |
| module. |
| (Contributed by P.Y. Developer; :issue:`12345`.) |
| |
| This saves the maintainer some effort going through the SVN logs |
| when researching a change. |
| |
| This article explains the new features in Python 2.7. The final |
| release of 2.7 is currently scheduled for July 2010; the detailed |
| schedule is described in :pep:`373`. |
| |
| Numeric handling has been improved in many ways, for both |
| floating-point numbers and for the :class:`Decimal` class. There are |
| some useful additions to the standard library, such as a greatly |
| enhanced :mod:`unittest` module, the :mod:`argparse` module for |
| parsing command-line options, convenient ordered-dictionary and |
| :class:`Counter` classes in the :mod:`collections` module, and many |
| other improvements. |
| |
| Python 2.7 is planned to be the last of the 2.x releases, so we worked |
| on making it a good release for the long term. To help with porting |
| to Python 3, several new features from the Python 3.x series have been |
| included in 2.7. |
| |
| This article doesn't attempt to provide a complete specification of |
| the new features, but instead provides a convenient overview. For |
| full details, you should refer to the documentation for Python 2.7 at |
| http://docs.python.org. If you want to understand the rationale for |
| the design and implementation, refer to the PEP for a particular new |
| feature or the issue on http://bugs.python.org in which a change was |
| discussed. Whenever possible, "What's New in Python" links to the |
| bug/patch item for each change. |
| |
| .. _whatsnew27-python31: |
| |
| The Future for Python 2.x |
| ========================= |
| |
| Python 2.7 is intended to be the last major release in the 2.x series. |
| The Python maintainers are planning to focus their future efforts on |
| the Python 3.x series. |
| |
| This means that 2.7 will remain in place for a long time, running |
| production systems that have not been ported to Python 3.x. |
| Two consequences of the long-term significance of 2.7 are: |
| |
| * It's very likely the 2.7 release will have a longer period of |
| maintenance compared to earlier 2.x versions. Python 2.7 will |
| continue to be maintained while the transition to 3.x continues, and |
| the developers are planning to support Python 2.7 with bug-fix |
| releases beyond the typical two years. |
| |
| * A policy decision was made to silence warnings only of interest to |
| developers. :exc:`DeprecationWarning` and its |
| descendants are now ignored unless otherwise requested, preventing |
| users from seeing warnings triggered by an application. This change |
| was also made in the branch that will become Python 3.2. (Discussed |
| on stdlib-sig and carried out in :issue:`7319`.) |
| |
| In previous releases, :exc:`DeprecationWarning` messages were |
| enabled by default, providing Python developers with a clear |
| indication of where their code may break in a future major version |
| of Python. |
| |
| However, there are increasingly many users of Python-based |
| applications who are not directly involved in the development of |
| those applications. :exc:`DeprecationWarning` messages are |
| irrelevant to such users, making them worry about an application |
| that's actually working correctly and burdening application developers |
| with responding to these concerns. |
| |
| You can re-enable display of :exc:`DeprecationWarning` messages by |
| running Python with the :option:`-Wdefault` (short form: |
| :option:`-Wd`) switch, or by setting the :envvar:`PYTHONWARNINGS` |
| environment variable to ``"default"`` (or ``"d"``) before running |
| Python. Python code can also re-enable them |
| by calling ``warnings.simplefilter('default')``. |
| |
| |
| Python 3.1 Features |
| ======================= |
| |
| Much as Python 2.6 incorporated features from Python 3.0, |
| version 2.7 incorporates some of the new features |
| in Python 3.1. The 2.x series continues to provide tools |
| for migrating to the 3.x series. |
| |
| A partial list of 3.1 features that were backported to 2.7: |
| |
| * The syntax for set literals (``{1,2,3}`` is a mutable set). |
| * Dictionary and set comprehensions (``{ i: i*2 for i in range(3)}``). |
| * Multiple context managers in a single :keyword:`with` statement. |
| * A new version of the :mod:`io` library, rewritten in C for performance. |
| * The ordered-dictionary type described in :ref:`pep-0372`. |
| * The new ``","`` format specifier described in :ref:`pep-0378`. |
| * The :class:`memoryview` object. |
| * A small subset of the :mod:`importlib` module, |
| `described below <#importlib-section>`__. |
| * Float-to-string and string-to-float conversions now round their |
| results more correctly, and :func:`repr` of a floating-point |
| number *x* returns a result that's guaranteed to round back to the |
| same number when converted back to a float. |
| * The :ctype:`PyCapsule` type, used to provide a C API for extension modules. |
| * The :cfunc:`PyLong_AsLongAndOverflow` C API function. |
| |
| Other new Python3-mode warnings include: |
| |
| * :func:`operator.isCallable` and :func:`operator.sequenceIncludes`, |
| which are not supported in 3.x, now trigger warnings. |
| * The :option:`-3` switch now automatically |
| enables the :option:`-Qwarn` switch that causes warnings |
| about using classic division with integers and long integers. |
| |
| |
| |
| .. ======================================================================== |
| .. Large, PEP-level features and changes should be described here. |
| .. ======================================================================== |
| |
| .. _pep-0372: |
| |
| PEP 372: Adding an Ordered Dictionary to collections |
| ==================================================== |
| |
| Regular Python dictionaries iterate over key/value pairs in arbitrary order. |
| Over the years, a number of authors have written alternative implementations |
| that remember the order that the keys were originally inserted. Based on |
| the experiences from those implementations, 2.7 introduces a new |
| :class:`~collections.OrderedDict` class in the :mod:`collections` module. |
| |
| The :class:`~collections.OrderedDict` API provides the same interface as regular |
| dictionaries but iterates over keys and values in a guaranteed order |
| depending on when a key was first inserted:: |
| |
| >>> from collections import OrderedDict |
| >>> d = OrderedDict([('first', 1), |
| ... ('second', 2), |
| ... ('third', 3)]) |
| >>> d.items() |
| [('first', 1), ('second', 2), ('third', 3)] |
| |
| If a new entry overwrites an existing entry, the original insertion |
| position is left unchanged:: |
| |
| >>> d['second'] = 4 |
| >>> d.items() |
| [('first', 1), ('second', 4), ('third', 3)] |
| |
| Deleting an entry and reinserting it will move it to the end:: |
| |
| >>> del d['second'] |
| >>> d['second'] = 5 |
| >>> d.items() |
| [('first', 1), ('third', 3), ('second', 5)] |
| |
| The :meth:`~collections.OrderedDict.popitem` method has an optional *last* |
| argument that defaults to True. If *last* is True, the most recently |
| added key is returned and removed; if it's False, the |
| oldest key is selected:: |
| |
| >>> od = OrderedDict([(x,0) for x in range(20)]) |
| >>> od.popitem() |
| (19, 0) |
| >>> od.popitem() |
| (18, 0) |
| >>> od.popitem(last=False) |
| (0, 0) |
| >>> od.popitem(last=False) |
| (1, 0) |
| |
| Comparing two ordered dictionaries checks both the keys and values, |
| and requires that the insertion order was the same:: |
| |
| >>> od1 = OrderedDict([('first', 1), |
| ... ('second', 2), |
| ... ('third', 3)]) |
| >>> od2 = OrderedDict([('third', 3), |
| ... ('first', 1), |
| ... ('second', 2)]) |
| >>> od1 == od2 |
| False |
| >>> # Move 'third' key to the end |
| >>> del od2['third']; od2['third'] = 3 |
| >>> od1 == od2 |
| True |
| |
| Comparing an :class:`~collections.OrderedDict` with a regular dictionary |
| ignores the insertion order and just compares the keys and values. |
| |
| How does the :class:`~collections.OrderedDict` work? It maintains a |
| doubly-linked list of keys, appending new keys to the list as they're inserted. |
| A secondary dictionary maps keys to their corresponding list node, so |
| deletion doesn't have to traverse the entire linked list and therefore |
| remains O(1). |
| |
| The standard library now supports use of ordered dictionaries in several |
| modules. |
| |
| * The :mod:`ConfigParser` module uses them by default, meaning that |
| configuration files can now read, modified, and then written back |
| in their original order. |
| |
| * The :meth:`~collections.somenamedtuple._asdict()` method for |
| :func:`collections.namedtuple` now returns an ordered dictionary with the |
| values appearing in the same order as the underlying tuple indices. |
| |
| * The :mod:`json` module's :class:`~json.JSONDecoder` class |
| constructor was extended with an *object_pairs_hook* parameter to |
| allow :class:`OrderedDict` instances to be built by the decoder. |
| Support was also added for third-party tools like |
| `PyYAML <http://pyyaml.org/>`_. |
| |
| .. seealso:: |
| |
| :pep:`372` - Adding an ordered dictionary to collections |
| PEP written by Armin Ronacher and Raymond Hettinger; |
| implemented by Raymond Hettinger. |
| |
| .. _pep-0378: |
| |
| PEP 378: Format Specifier for Thousands Separator |
| ================================================= |
| |
| To make program output more readable, it can be useful to add |
| separators to large numbers, rendering them as |
| 18,446,744,073,709,551,616 instead of 18446744073709551616. |
| |
| The fully general solution for doing this is the :mod:`locale` module, |
| which can use different separators ("," in North America, "." in |
| Europe) and different grouping sizes, but :mod:`locale` is complicated |
| to use and unsuitable for multi-threaded applications where different |
| threads are producing output for different locales. |
| |
| Therefore, a simple comma-grouping mechanism has been added to the |
| mini-language used by the :meth:`str.format` method. When |
| formatting a floating-point number, simply include a comma between the |
| width and the precision:: |
| |
| >>> '{:20,.2f}'.format(18446744073709551616.0) |
| '18,446,744,073,709,551,616.00' |
| |
| When formatting an integer, include the comma after the width: |
| |
| >>> '{:20,d}'.format(18446744073709551616) |
| '18,446,744,073,709,551,616' |
| |
| This mechanism is not adaptable at all; commas are always used as the |
| separator and the grouping is always into three-digit groups. The |
| comma-formatting mechanism isn't as general as the :mod:`locale` |
| module, but it's easier to use. |
| |
| .. seealso:: |
| |
| :pep:`378` - Format Specifier for Thousands Separator |
| PEP written by Raymond Hettinger; implemented by Eric Smith. |
| |
| PEP 389: The argparse Module for Parsing Command Lines |
| ====================================================== |
| |
| The :mod:`argparse` module for parsing command-line arguments was |
| added as a more powerful replacement for the |
| :mod:`optparse` module. |
| |
| This means Python now supports three different modules for parsing |
| command-line arguments: :mod:`getopt`, :mod:`optparse`, and |
| :mod:`argparse`. The :mod:`getopt` module closely resembles the C |
| library's :cfunc:`getopt` function, so it remains useful if you're writing a |
| Python prototype that will eventually be rewritten in C. |
| :mod:`optparse` becomes redundant, but there are no plans to remove it |
| because there are many scripts still using it, and there's no |
| automated way to update these scripts. (Making the :mod:`argparse` |
| API consistent with :mod:`optparse`'s interface was discussed but |
| rejected as too messy and difficult.) |
| |
| In short, if you're writing a new script and don't need to worry |
| about compatibility with earlier versions of Python, use |
| :mod:`argparse` instead of :mod:`optparse`. |
| |
| Here's an example:: |
| |
| import argparse |
| |
| parser = argparse.ArgumentParser(description='Command-line example.') |
| |
| # Add optional switches |
| parser.add_argument('-v', action='store_true', dest='is_verbose', |
| help='produce verbose output') |
| parser.add_argument('-o', action='store', dest='output', |
| metavar='FILE', |
| help='direct output to FILE instead of stdout') |
| parser.add_argument('-C', action='store', type=int, dest='context', |
| metavar='NUM', default=0, |
| help='display NUM lines of added context') |
| |
| # Allow any number of additional arguments. |
| parser.add_argument(nargs='*', action='store', dest='inputs', |
| help='input filenames (default is stdin)') |
| |
| args = parser.parse_args() |
| print args.__dict__ |
| |
| Unless you override it, :option:`-h` and :option:`--help` switches |
| are automatically added, and produce neatly formatted output:: |
| |
| -> ./python.exe argparse-example.py --help |
| usage: argparse-example.py [-h] [-v] [-o FILE] [-C NUM] [inputs [inputs ...]] |
| |
| Command-line example. |
| |
| positional arguments: |
| inputs input filenames (default is stdin) |
| |
| optional arguments: |
| -h, --help show this help message and exit |
| -v produce verbose output |
| -o FILE direct output to FILE instead of stdout |
| -C NUM display NUM lines of added context |
| |
| As with :mod:`optparse`, the command-line switches and arguments |
| are returned as an object with attributes named by the *dest* parameters:: |
| |
| -> ./python.exe argparse-example.py -v |
| {'output': None, |
| 'is_verbose': True, |
| 'context': 0, |
| 'inputs': []} |
| |
| -> ./python.exe argparse-example.py -v -o /tmp/output -C 4 file1 file2 |
| {'output': '/tmp/output', |
| 'is_verbose': True, |
| 'context': 4, |
| 'inputs': ['file1', 'file2']} |
| |
| :mod:`argparse` has much fancier validation than :mod:`optparse`; you |
| can specify an exact number of arguments as an integer, 0 or more |
| arguments by passing ``'*'``, 1 or more by passing ``'+'``, or an |
| optional argument with ``'?'``. A top-level parser can contain |
| sub-parsers to define subcommands that have different sets of |
| switches, as in ``svn commit``, ``svn checkout``, etc. You can |
| specify an argument's type as :class:`~argparse.FileType`, which will |
| automatically open files for you and understands that ``'-'`` means |
| standard input or output. |
| |
| .. seealso:: |
| |
| `argparse module documentation <http://docs.python.org/dev/library/argparse.html>`__ |
| |
| `Upgrading optparse code to use argparse <http://docs.python.org/dev/library/argparse.html#upgrading-optparse-code>`__ |
| Part of the Python documentation, describing how to convert |
| code that uses :mod:`optparse`. |
| |
| :pep:`389` - argparse - New Command Line Parsing Module |
| PEP written and implemented by Steven Bethard. |
| |
| PEP 391: Dictionary-Based Configuration For Logging |
| ==================================================== |
| |
| .. XXX not documented in library reference yet; add link here once it's added. |
| |
| The :mod:`logging` module is very flexible; applications can define |
| a tree of logging subsystems, and each logger in this tree can filter |
| out certain messages, format them differently, and direct messages to |
| a varying number of handlers. |
| |
| All this flexibility can require a lot of configuration. You can |
| write Python statements to create objects and set their properties, |
| but a complex set-up requires verbose but boring code. |
| :mod:`logging` also supports a :func:`~logging.config.fileConfig` |
| function that parses a file, but the file format doesn't support |
| configuring filters, and it's messier to generate programmatically. |
| |
| Python 2.7 adds a :func:`~logging.config.dictConfig` function that |
| uses a dictionary to configure logging. There are many ways to |
| produce a dictionary from different sources: construct one with code; |
| parse a file containing JSON; or use a YAML parsing library if one is |
| installed. |
| |
| The following example configures two loggers, the root logger and a |
| logger named "network". Messages sent to the root logger will be |
| sent to the system log using the syslog protocol, and messages |
| to the "network" logger will be written to a :file:`network.log` file |
| that will be rotated once the log reaches 1Mb. |
| |
| :: |
| |
| import logging |
| import logging.config |
| |
| configdict = { |
| 'version': 1, # Configuration schema in use; must be 1 for now |
| 'formatters': { |
| 'standard': { |
| 'format': ('%(asctime)s %(name)-15s ' |
| '%(levelname)-8s %(message)s')}}, |
| |
| 'handlers': {'netlog': {'backupCount': 10, |
| 'class': 'logging.handlers.RotatingFileHandler', |
| 'filename': '/logs/network.log', |
| 'formatter': 'standard', |
| 'level': 'INFO', |
| 'maxBytes': 1024*1024}, |
| 'syslog': {'class': 'logging.handlers.SysLogHandler', |
| 'formatter': 'standard', |
| 'level': 'ERROR'}}, |
| |
| # Specify all the subordinate loggers |
| 'loggers': { |
| 'network': { |
| 'handlers': ['netlog'] |
| } |
| }, |
| # Specify properties of the root logger |
| 'root': { |
| 'handlers': ['syslog'] |
| }, |
| } |
| |
| # Set up configuration |
| logging.config.dictConfig(configdict) |
| |
| # As an example, log two error messages |
| logger = logging.getLogger('/') |
| logger.error('Database not found') |
| |
| netlogger = logging.getLogger('network') |
| netlogger.error('Connection failed') |
| |
| Three smaller enhancements to the :mod:`logging` module, all |
| implemented by Vinay Sajip, are: |
| |
| .. rev79293 |
| |
| * The :class:`~logging.handlers.SysLogHandler` class now supports |
| syslogging over TCP. The constructor has a *socktype* parameter |
| giving the type of socket to use, either :const:`socket.SOCK_DGRAM` |
| for UDP or :const:`socket.SOCK_STREAM` for TCP. The default |
| protocol remains UDP. |
| |
| * :class:`Logger` instances gained a :meth:`getChild` method that retrieves a |
| descendant logger using a relative path. For example, |
| once you retrieve a logger by doing ``log = getLogger('app')``, |
| calling ``log.getChild('network.listen')`` is equivalent to |
| ``getLogger('app.network.listen')``. |
| |
| * The :class:`LoggerAdapter` class gained a :meth:`isEnabledFor` method |
| that takes a *level* and returns whether the underlying logger would |
| process a message of that level of importance. |
| |
| .. seealso:: |
| |
| :pep:`391` - Dictionary-Based Configuration For Logging |
| PEP written and implemented by Vinay Sajip. |
| |
| PEP 3106: Dictionary Views |
| ==================================================== |
| |
| The dictionary methods :meth:`keys`, :meth:`values`, and :meth:`items` |
| are different in Python 3.x. They return an object called a :dfn:`view` |
| instead of a fully materialized list. |
| |
| It's not possible to change the return values of :meth:`keys`, |
| :meth:`values`, and :meth:`items` in Python 2.7 because too much code |
| would break. Instead the 3.x versions were added under the new names |
| :meth:`viewkeys`, :meth:`viewvalues`, and :meth:`viewitems`. |
| |
| :: |
| |
| >>> d = dict((i*10, chr(65+i)) for i in range(26)) |
| >>> d |
| {0: 'A', 130: 'N', 10: 'B', 140: 'O', 20: ..., 250: 'Z'} |
| >>> d.viewkeys() |
| dict_keys([0, 130, 10, 140, 20, 150, 30, ..., 250]) |
| |
| Views can be iterated over, but the key and item views also behave |
| like sets. The ``&`` operator performs intersection, and ``|`` |
| performs a union:: |
| |
| >>> d1 = dict((i*10, chr(65+i)) for i in range(26)) |
| >>> d2 = dict((i**.5, i) for i in range(1000)) |
| >>> d1.viewkeys() & d2.viewkeys() |
| set([0.0, 10.0, 20.0, 30.0]) |
| >>> d1.viewkeys() | range(0, 30) |
| set([0, 1, 130, 3, 4, 5, 6, ..., 120, 250]) |
| |
| The view keeps track of the dictionary and its contents change as the |
| dictionary is modified:: |
| |
| >>> vk = d.viewkeys() |
| >>> vk |
| dict_keys([0, 130, 10, ..., 250]) |
| >>> d[260] = '&' |
| >>> vk |
| dict_keys([0, 130, 260, 10, ..., 250]) |
| |
| However, note that you can't add or remove keys while you're iterating |
| over the view:: |
| |
| >>> for k in vk: |
| ... d[k*2] = k |
| ... |
| Traceback (most recent call last): |
| File "<stdin>", line 1, in <module> |
| RuntimeError: dictionary changed size during iteration |
| |
| You can use the view methods in Python 2.x code, and the 2to3 |
| converter will change them to the standard :meth:`keys`, |
| :meth:`values`, and :meth:`items` methods. |
| |
| .. seealso:: |
| |
| :pep:`3106` - Revamping dict.keys(), .values() and .items() |
| PEP written by Guido van Rossum. |
| Backported to 2.7 by Alexandre Vassalotti; :issue:`1967`. |
| |
| |
| PEP 3137: The memoryview Object |
| ==================================================== |
| |
| The :class:`memoryview` object provides a view of another object's |
| memory content that matches the :class:`bytes` type's interface. |
| |
| >>> import string |
| >>> m = memoryview(string.letters) |
| >>> m |
| <memory at 0x37f850> |
| >>> len(m) # Returns length of underlying object |
| 52 |
| >>> m[0], m[25], m[26] # Indexing returns one byte |
| ('a', 'z', 'A') |
| >>> m2 = m[0:26] # Slicing returns another memoryview |
| >>> m2 |
| <memory at 0x37f080> |
| |
| The content of the view can be converted to a string of bytes or |
| a list of integers: |
| |
| >>> m2.tobytes() |
| 'abcdefghijklmnopqrstuvwxyz' |
| >>> m2.tolist() |
| [97, 98, 99, 100, 101, 102, 103, ... 121, 122] |
| >>> |
| |
| :class:`memoryview` objects allow modifying the underlying object if |
| it's a mutable object. |
| |
| >>> m2[0] = 75 |
| Traceback (most recent call last): |
| File "<stdin>", line 1, in <module> |
| TypeError: cannot modify read-only memory |
| >>> b = bytearray(string.letters) # Creating a mutable object |
| >>> b |
| bytearray(b'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ') |
| >>> mb = memoryview(b) |
| >>> mb[0] = '*' # Assign to view, changing the bytearray. |
| >>> b[0:5] # The bytearray has been changed. |
| bytearray(b'*bcde') |
| >>> |
| |
| .. seealso:: |
| |
| :pep:`3137` - Immutable Bytes and Mutable Buffer |
| PEP written by Guido van Rossum. |
| Implemented by Travis Oliphant, Antoine Pitrou and others. |
| Backported to 2.7 by Antoine Pitrou; :issue:`2396`. |
| |
| |
| |
| Other Language Changes |
| ====================== |
| |
| Some smaller changes made to the core Python language are: |
| |
| * The syntax for set literals has been backported from Python 3.x. |
| Curly brackets are used to surround the contents of the resulting |
| mutable set; set literals are |
| distinguished from dictionaries by not containing colons and values. |
| ``{}`` continues to represent an empty dictionary; use |
| ``set()`` for an empty set. |
| |
| >>> {1,2,3,4,5} |
| set([1, 2, 3, 4, 5]) |
| >>> set() # empty set |
| set([]) |
| >>> {} # empty dict |
| {} |
| |
| Backported by Alexandre Vassalotti; :issue:`2335`. |
| |
| * Dictionary and set comprehensions are another feature backported from |
| 3.x, generalizing list/generator comprehensions to use |
| the literal syntax for sets and dictionaries. |
| |
| >>> {x: x*x for x in range(6)} |
| {0: 0, 1: 1, 2: 4, 3: 9, 4: 16, 5: 25} |
| >>> {('a'*x) for x in range(6)} |
| set(['', 'a', 'aa', 'aaa', 'aaaa', 'aaaaa']) |
| |
| Backported by Alexandre Vassalotti; :issue:`2333`. |
| |
| * The :keyword:`with` statement can now use multiple context managers |
| in one statement. Context managers are processed from left to right |
| and each one is treated as beginning a new :keyword:`with` statement. |
| This means that:: |
| |
| with A() as a, B() as b: |
| ... suite of statements ... |
| |
| is equivalent to:: |
| |
| with A() as a: |
| with B() as b: |
| ... suite of statements ... |
| |
| The :func:`contextlib.nested` function provides a very similar |
| function, so it's no longer necessary and has been deprecated. |
| |
| (Proposed in http://codereview.appspot.com/53094; implemented by |
| Georg Brandl.) |
| |
| * Conversions between floating-point numbers and strings are |
| now correctly rounded on most platforms. These conversions occur |
| in many different places: :func:`str` on |
| floats and complex numbers; the :class:`float` and :class:`complex` |
| constructors; |
| numeric formatting; serializing and |
| deserializing floats and complex numbers using the |
| :mod:`marshal`, :mod:`pickle` |
| and :mod:`json` modules; |
| parsing of float and imaginary literals in Python code; |
| and :class:`~decimal.Decimal`-to-float conversion. |
| |
| Related to this, the :func:`repr` of a floating-point number *x* |
| now returns a result based on the shortest decimal string that's |
| guaranteed to round back to *x* under correct rounding (with |
| round-half-to-even rounding mode). Previously it gave a string |
| based on rounding x to 17 decimal digits. |
| |
| .. maybe add an example? |
| |
| The rounding library responsible for this improvement works on |
| Windows and on Unix platforms using the gcc, icc, or suncc |
| compilers. There may be a small number of platforms where correct |
| operation of this code cannot be guaranteed, so the code is not |
| used on such systems. You can find out which code is being used |
| by checking :data:`sys.float_repr_style`, which will be ``short`` |
| if the new code is in use and ``legacy`` if it isn't. |
| |
| Implemented by Eric Smith and Mark Dickinson, using David Gay's |
| :file:`dtoa.c` library; :issue:`7117`. |
| |
| * Conversions from long integers and regular integers to floating |
| point now round differently, returning the floating-point number |
| closest to the number. This doesn't matter for small integers that |
| can be converted exactly, but for large numbers that will |
| unavoidably lose precision, Python 2.7 now approximates more |
| closely. For example, Python 2.6 computed the following:: |
| |
| >>> n = 295147905179352891391 |
| >>> float(n) |
| 2.9514790517935283e+20 |
| >>> n - long(float(n)) |
| 65535L |
| |
| Python 2.7's floating-point result is larger, but much closer to the |
| true value:: |
| |
| >>> n = 295147905179352891391 |
| >>> float(n) |
| 2.9514790517935289e+20 |
| >>> n - long(float(n)) |
| -1L |
| |
| (Implemented by Mark Dickinson; :issue:`3166`.) |
| |
| Integer division is also more accurate in its rounding behaviours. (Also |
| implemented by Mark Dickinson; :issue:`1811`.) |
| |
| * Implicit coercion for complex numbers has been removed; the interpreter |
| will no longer ever attempt to call a :meth:`__coerce__` method on complex |
| objects. (Removed by Meador Inge and Mark Dickinson; :issue:`5211`.) |
| |
| * The :meth:`str.format` method now supports automatic numbering of the replacement |
| fields. This makes using :meth:`str.format` more closely resemble using |
| ``%s`` formatting:: |
| |
| >>> '{}:{}:{}'.format(2009, 04, 'Sunday') |
| '2009:4:Sunday' |
| >>> '{}:{}:{day}'.format(2009, 4, day='Sunday') |
| '2009:4:Sunday' |
| |
| The auto-numbering takes the fields from left to right, so the first ``{...}`` |
| specifier will use the first argument to :meth:`str.format`, the next |
| specifier will use the next argument, and so on. You can't mix auto-numbering |
| and explicit numbering -- either number all of your specifier fields or none |
| of them -- but you can mix auto-numbering and named fields, as in the second |
| example above. (Contributed by Eric Smith; :issue:`5237`.) |
| |
| Complex numbers now correctly support usage with :func:`format`, |
| and default to being right-aligned. |
| Specifying a precision or comma-separation applies to both the real |
| and imaginary parts of the number, but a specified field width and |
| alignment is applied to the whole of the resulting ``1.5+3j`` |
| output. (Contributed by Eric Smith; :issue:`1588` and :issue:`7988`.) |
| |
| The 'F' format code now always formats its output using uppercase characters, |
| so it will now produce 'INF' and 'NAN'. |
| (Contributed by Eric Smith; :issue:`3382`.) |
| |
| A low-level change: the :meth:`object.__format__` method now triggers |
| a :exc:`PendingDeprecationWarning` if it's passed a format string, |
| because the :meth:`__format__` method for :class:`object` converts |
| the object to a string representation and formats that. Previously |
| the method silently applied the format string to the string |
| representation, but that could hide mistakes in Python code. If |
| you're supplying formatting information such as an alignment or |
| precision, presumably you're expecting the formatting to be applied |
| in some object-specific way. (Fixed by Eric Smith; :issue:`7994`.) |
| |
| * The :func:`int` and :func:`long` types gained a ``bit_length`` |
| method that returns the number of bits necessary to represent |
| its argument in binary:: |
| |
| >>> n = 37 |
| >>> bin(n) |
| '0b100101' |
| >>> n.bit_length() |
| 6 |
| >>> n = 2**123-1 |
| >>> n.bit_length() |
| 123 |
| >>> (n+1).bit_length() |
| 124 |
| |
| (Contributed by Fredrik Johansson and Victor Stinner; :issue:`3439`.) |
| |
| * The :keyword:`import` statement will no longer try a relative import |
| if an absolute import (e.g. ``from .os import sep``) fails. This |
| fixes a bug, but could possibly break certain :keyword:`import` |
| statements that were only working by accident. (Fixed by Meador Inge; |
| :issue:`7902`.) |
| |
| * It's now possible for a subclass of the built-in :class:`unicode` type |
| to override the :meth:`__unicode__` method. (Implemented by |
| Victor Stinner; :issue:`1583863`.) |
| |
| * The :class:`bytearray` type's :meth:`~bytearray.translate` method now accepts |
| ``None`` as its first argument. (Fixed by Georg Brandl; |
| :issue:`4759`.) |
| |
| .. bytearray doesn't seem to be documented |
| |
| * When using ``@classmethod`` and ``@staticmethod`` to wrap |
| methods as class or static methods, the wrapper object now |
| exposes the wrapped function as their :attr:`__func__` attribute. |
| (Contributed by Amaury Forgeot d'Arc, after a suggestion by |
| George Sakkis; :issue:`5982`.) |
| |
| * When a restricted set of attributes were set using ``__slots__``, |
| deleting an unset attribute would not raise :exc:`AttributeError` |
| as you would expect. Fixed by Benjamin Peterson; :issue:`7604`.) |
| |
| * Two new encodings are now supported: "cp720", used primarily for |
| Arabic text; and "cp858", a variant of CP 850 that adds the euro |
| symbol. (CP720 contributed by Alexander Belchenko and Amaury |
| Forgeot d'Arc in :issue:`1616979`; CP858 contributed by Tim Hatch in |
| :issue:`8016`.) |
| |
| * The :class:`file` object will now set the :attr:`filename` attribute |
| on the :exc:`IOError` exception when trying to open a directory |
| on POSIX platforms (noted by Jan Kaliszewski; :issue:`4764`), and |
| now explicitly checks for and forbids writing to read-only file objects |
| instead of trusting the C library to catch and report the error |
| (fixed by Stefan Krah; :issue:`5677`). |
| |
| * The Python tokenizer now translates line endings itself, so the |
| :func:`compile` built-in function now accepts code using any |
| line-ending convention. Additionally, it no longer requires that the |
| code end in a newline. |
| |
| * Extra parentheses in function definitions are illegal in Python 3.x, |
| meaning that you get a syntax error from ``def f((x)): pass``. In |
| Python3-warning mode, Python 2.7 will now warn about this odd usage. |
| (Noted by James Lingard; :issue:`7362`.) |
| |
| * It's now possible to create weak references to old-style class |
| objects. New-style classes were always weak-referenceable. (Fixed |
| by Antoine Pitrou; :issue:`8268`.) |
| |
| * When a module object is garbage-collected, the module's dictionary is |
| now only cleared if no one else is holding a reference to the |
| dictionary (:issue:`7140`). |
| |
| .. ====================================================================== |
| |
| .. _new-27-interpreter: |
| |
| Interpreter Changes |
| ------------------------------- |
| |
| A new environment variable, :envvar:`PYTHONWARNINGS`, |
| allows controlling warnings. It should be set to a string |
| containing warning settings, equivalent to those |
| used with the :option:`-W` switch, separated by commas. |
| (Contributed by Brian Curtin; :issue:`7301`.) |
| |
| For example, the following setting will print warnings every time |
| they occur, but turn warnings from the :mod:`Cookie` module into an |
| error. (The exact syntax for setting an environment variable varies |
| across operating systems and shells.) |
| |
| :: |
| |
| export PYTHONWARNINGS=all,error:::Cookie:0 |
| |
| .. ====================================================================== |
| |
| |
| Optimizations |
| ------------- |
| |
| Several performance enhancements have been added: |
| |
| .. * A new :program:`configure` option, :option:`--with-computed-gotos`, |
| compiles the main bytecode interpreter loop using a new dispatch |
| mechanism that gives speedups of up to 20%, depending on the system |
| and benchmark. The new mechanism is only supported on certain |
| compilers, such as gcc, SunPro, and icc. |
| |
| * A new opcode was added to perform the initial setup for |
| :keyword:`with` statements, looking up the :meth:`__enter__` and |
| :meth:`__exit__` methods. (Contributed by Benjamin Peterson.) |
| |
| * The garbage collector now performs better for one common usage |
| pattern: when many objects are being allocated without deallocating |
| any of them. This would previously take quadratic |
| time for garbage collection, but now the number of full garbage collections |
| is reduced as the number of objects on the heap grows. |
| The new logic only performs a full garbage collection pass when |
| the middle generation has been collected 10 times and when the |
| number of survivor objects from the middle generation exceeds 10% of |
| the number of objects in the oldest generation. (Suggested by Martin |
| von Löwis and implemented by Antoine Pitrou; :issue:`4074`.) |
| |
| * The garbage collector tries to avoid tracking simple containers |
| which can't be part of a cycle. In Python 2.7, this is now true for |
| tuples and dicts containing atomic types (such as ints, strings, |
| etc.). Transitively, a dict containing tuples of atomic types won't |
| be tracked either. This helps reduce the cost of each |
| garbage collection by decreasing the number of objects to be |
| considered and traversed by the collector. |
| (Contributed by Antoine Pitrou; :issue:`4688`.) |
| |
| * Long integers are now stored internally either in base 2**15 or in base |
| 2**30, the base being determined at build time. Previously, they |
| were always stored in base 2**15. Using base 2**30 gives |
| significant performance improvements on 64-bit machines, but |
| benchmark results on 32-bit machines have been mixed. Therefore, |
| the default is to use base 2**30 on 64-bit machines and base 2**15 |
| on 32-bit machines; on Unix, there's a new configure option |
| :option:`--enable-big-digits` that can be used to override this default. |
| |
| Apart from the performance improvements this change should be |
| invisible to end users, with one exception: for testing and |
| debugging purposes there's a new structseq :data:`sys.long_info` that |
| provides information about the internal format, giving the number of |
| bits per digit and the size in bytes of the C type used to store |
| each digit:: |
| |
| >>> import sys |
| >>> sys.long_info |
| sys.long_info(bits_per_digit=30, sizeof_digit=4) |
| |
| (Contributed by Mark Dickinson; :issue:`4258`.) |
| |
| Another set of changes made long objects a few bytes smaller: 2 bytes |
| smaller on 32-bit systems and 6 bytes on 64-bit. |
| (Contributed by Mark Dickinson; :issue:`5260`.) |
| |
| * The division algorithm for long integers has been made faster |
| by tightening the inner loop, doing shifts instead of multiplications, |
| and fixing an unnecessary extra iteration. |
| Various benchmarks show speedups of between 50% and 150% for long |
| integer divisions and modulo operations. |
| (Contributed by Mark Dickinson; :issue:`5512`.) |
| Bitwise operations are also significantly faster (initial patch by |
| Gregory Smith; :issue:`1087418`). |
| |
| * The implementation of ``%`` checks for the left-side operand being |
| a Python string and special-cases it; this results in a 1-3% |
| performance increase for applications that frequently use ``%`` |
| with strings, such as templating libraries. |
| (Implemented by Collin Winter; :issue:`5176`.) |
| |
| * List comprehensions with an ``if`` condition are compiled into |
| faster bytecode. (Patch by Antoine Pitrou, back-ported to 2.7 |
| by Jeffrey Yasskin; :issue:`4715`.) |
| |
| * Converting an integer or long integer to a decimal string was made |
| faster by special-casing base 10 instead of using a generalized |
| conversion function that supports arbitrary bases. |
| (Patch by Gawain Bolton; :issue:`6713`.) |
| |
| * The :meth:`split`, :meth:`replace`, :meth:`rindex`, |
| :meth:`rpartition`, and :meth:`rsplit` methods of string-like types |
| (strings, Unicode strings, and :class:`bytearray` objects) now use a |
| fast reverse-search algorithm instead of a character-by-character |
| scan. This is sometimes faster by a factor of 10. (Added by |
| Florent Xicluna; :issue:`7462` and :issue:`7622`.) |
| |
| * The :mod:`pickle` and :mod:`cPickle` modules now automatically |
| intern the strings used for attribute names, reducing memory usage |
| of the objects resulting from unpickling. (Contributed by Jake |
| McGuire; :issue:`5084`.) |
| |
| * The :mod:`cPickle` module now special-cases dictionaries, |
| nearly halving the time required to pickle them. |
| (Contributed by Collin Winter; :issue:`5670`.) |
| |
| .. ====================================================================== |
| |
| New and Improved Modules |
| ======================== |
| |
| As in every release, Python's standard library received a number of |
| enhancements and bug fixes. Here's a partial list of the most notable |
| changes, sorted alphabetically by module name. Consult the |
| :file:`Misc/NEWS` file in the source tree for a more complete list of |
| changes, or look through the Subversion logs for all the details. |
| |
| * The :mod:`bdb` module's base debugging class :class:`~bdb.Bdb` |
| gained a feature for skipping modules. The constructor |
| now takes an iterable containing glob-style patterns such as |
| ``django.*``; the debugger will not step into stack frames |
| from a module that matches one of these patterns. |
| (Contributed by Maru Newby after a suggestion by |
| Senthil Kumaran; :issue:`5142`.) |
| |
| * The :mod:`binascii` module now supports the buffer API, so it can be |
| used with :class:`memoryview` instances and other similar buffer objects. |
| (Backported from 3.x by Florent Xicluna; :issue:`7703`.) |
| |
| * Updated module: the :mod:`bsddb` module has been updated from 4.7.2devel9 |
| to version 4.8.4 of |
| `the pybsddb package <http://www.jcea.es/programacion/pybsddb.htm>`__. |
| The new version features better Python 3.x compatibility, various bug fixes, |
| and adds several new BerkeleyDB flags and methods. |
| (Updated by Jesús Cea Avión; :issue:`8156`. The pybsddb |
| changelog can be read at http://hg.jcea.es/pybsddb/file/tip/ChangeLog.) |
| |
| * The :mod:`bz2` module's :class:`~bz2.BZ2File` now supports the context |
| management protocol, so you can write ``with bz2.BZ2File(...) as f:``. |
| (Contributed by Hagen Fürstenau; :issue:`3860`.) |
| |
| * New class: the :class:`~collections.Counter` class in the :mod:`collections` |
| module is useful for tallying data. :class:`~collections.Counter` instances |
| behave mostly like dictionaries but return zero for missing keys instead of |
| raising a :exc:`KeyError`: |
| |
| .. doctest:: |
| :options: +NORMALIZE_WHITESPACE |
| |
| >>> from collections import Counter |
| >>> c = Counter() |
| >>> for letter in 'here is a sample of english text': |
| ... c[letter] += 1 |
| ... |
| >>> c |
| Counter({' ': 6, 'e': 5, 's': 3, 'a': 2, 'i': 2, 'h': 2, |
| 'l': 2, 't': 2, 'g': 1, 'f': 1, 'm': 1, 'o': 1, 'n': 1, |
| 'p': 1, 'r': 1, 'x': 1}) |
| >>> c['e'] |
| 5 |
| >>> c['z'] |
| 0 |
| |
| There are three additional :class:`~collections.Counter` methods. |
| :meth:`~collections.Counter.most_common` returns the N most common |
| elements and their counts. :meth:`~collections.Counter.elements` |
| returns an iterator over the contained elements, repeating each |
| element as many times as its count. |
| :meth:`~collections.Counter.subtract` takes an iterable and |
| subtracts one for each element instead of adding; if the argument is |
| a dictionary or another :class:`Counter`, the counts are |
| subtracted. :: |
| |
| >>> c.most_common(5) |
| [(' ', 6), ('e', 5), ('s', 3), ('a', 2), ('i', 2)] |
| >>> c.elements() -> |
| 'a', 'a', ' ', ' ', ' ', ' ', ' ', ' ', |
| 'e', 'e', 'e', 'e', 'e', 'g', 'f', 'i', 'i', |
| 'h', 'h', 'm', 'l', 'l', 'o', 'n', 'p', 's', |
| 's', 's', 'r', 't', 't', 'x' |
| >>> c['e'] |
| 5 |
| >>> c.subtract('very heavy on the letter e') |
| >>> c['e'] # Count is now lower |
| -1 |
| |
| Contributed by Raymond Hettinger; :issue:`1696199`. |
| |
| .. revision 79660 |
| |
| New class: :class:`~collections.OrderedDict` is described in the earlier |
| section :ref:`pep-0372`. |
| |
| New method: The :class:`~collections.deque` data type now has a |
| :meth:`~collections.deque.count` method that returns the number of |
| contained elements equal to the supplied argument *x*, and a |
| :meth:`~collections.deque.reverse` method that reverses the elements |
| of the deque in-place. :class:`deque` also exposes its maximum |
| length as the read-only :attr:`~collections.deque.maxlen` attribute. |
| (Both features added by Raymond Hettinger.) |
| |
| The :class:`~collections.namedtuple` class now has an optional *rename* parameter. |
| If *rename* is true, field names that are invalid because they've |
| been repeated or aren't legal Python identifiers will be |
| renamed to legal names that are derived from the field's |
| position within the list of fields: |
| |
| >>> from collections import namedtuple |
| >>> T = namedtuple('T', ['field1', '$illegal', 'for', 'field2'], rename=True) |
| >>> T._fields |
| ('field1', '_1', '_2', 'field2') |
| |
| (Added by Raymond Hettinger; :issue:`1818`.) |
| |
| Finally, the :class:`~collections.Mapping` abstract base class now |
| returns :const:`NotImplemented` if a mapping is compared to |
| another type that isn't a :class:`Mapping`. |
| (Fixed by Daniel Stutzbach; :issue:`8729`.) |
| |
| * Constructors for the parsing classes in the :mod:`ConfigParser` module now |
| take a *allow_no_value* parameter, defaulting to false; if true, |
| options without values will be allowed. For example:: |
| |
| >>> import ConfigParser, StringIO |
| >>> sample_config = """ |
| ... [mysqld] |
| ... user = mysql |
| ... pid-file = /var/run/mysqld/mysqld.pid |
| ... skip-bdb |
| ... """ |
| >>> config = ConfigParser.RawConfigParser(allow_no_value=True) |
| >>> config.readfp(StringIO.StringIO(sample_config)) |
| >>> config.get('mysqld', 'user') |
| 'mysql' |
| >>> print config.get('mysqld', 'skip-bdb') |
| None |
| >>> print config.get('mysqld', 'unknown') |
| Traceback (most recent call last): |
| ... |
| NoOptionError: No option 'unknown' in section: 'mysqld' |
| |
| (Contributed by Mats Kindahl; :issue:`7005`.) |
| |
| * Deprecated function: :func:`contextlib.nested`, which allows |
| handling more than one context manager with a single :keyword:`with` |
| statement, has been deprecated, because the :keyword:`with` statement |
| now supports multiple context managers. |
| |
| * The :mod:`cookielib` module now ignores cookies that have an invalid |
| version field, one that doesn't contain an integer value. (Fixed by |
| John J. Lee; :issue:`3924`.) |
| |
| * The :mod:`copy` module's :func:`~copy.deepcopy` function will now |
| correctly copy bound instance methods. (Implemented by |
| Robert Collins; :issue:`1515`.) |
| |
| * The :mod:`ctypes` module now always converts ``None`` to a C NULL |
| pointer for arguments declared as pointers. (Changed by Thomas |
| Heller; :issue:`4606`.) The underlying `libffi library |
| <http://sourceware.org/libffi/>`__ has been updated to version |
| 3.0.9, containing various fixes for different platforms. (Updated |
| by Matthias Klose; :issue:`8142`.) |
| |
| * New method: the :mod:`datetime` module's :class:`~datetime.timedelta` class |
| gained a :meth:`~datetime.timedelta.total_seconds` method that returns the |
| number of seconds in the duration. (Contributed by Brian Quinlan; :issue:`5788`.) |
| |
| * New method: the :class:`~decimal.Decimal` class gained a |
| :meth:`~decimal.Decimal.from_float` class method that performs an exact |
| conversion of a floating-point number to a :class:`~decimal.Decimal`. |
| This exact conversion strives for the |
| closest decimal approximation to the floating-point representation's value; |
| the resulting decimal value will therefore still include the inaccuracy, |
| if any. |
| For example, ``Decimal.from_float(0.1)`` returns |
| ``Decimal('0.1000000000000000055511151231257827021181583404541015625')``. |
| (Implemented by Raymond Hettinger; :issue:`4796`.) |
| |
| Comparing instances of :class:`Decimal` with floating-point |
| numbers now produces sensible results based on the numeric values |
| of the operands. Previously such comparisons would fall back to |
| Python's default rules for comparing objects, which produced arbitrary |
| results based on their type. Note that you still cannot combine |
| :class:`Decimal` and floating-point in other operations such as addition, |
| since you should be explicitly choosing how to convert between float and |
| :class:`Decimal`. |
| (Fixed by Mark Dickinson; :issue:`2531`.) |
| |
| The constructor for :class:`~decimal.Decimal` now accepts |
| floating-point numbers (added by Raymond Hettinger; :issue:`8257`) |
| and non-European Unicode characters such as Arabic-Indic digits |
| (contributed by Mark Dickinson; :issue:`6595`). |
| |
| Most of the methods of the :class:`~decimal.Context` class now accept integers |
| as well as :class:`~decimal.Decimal` instances; the only exceptions are the |
| :meth:`~decimal.Context.canonical` and :meth:`~decimal.Context.is_canonical` |
| methods. (Patch by Juan José Conti; :issue:`7633`.) |
| |
| When using :class:`~decimal.Decimal` instances with a string's |
| :meth:`~str.format` method, the default alignment was previously |
| left-alignment. This has been changed to right-alignment, which is |
| more sensible for numeric types. (Changed by Mark Dickinson; :issue:`6857`.) |
| |
| Comparisons involving a signaling NaN value (or ``sNAN``) now signal |
| :const:`InvalidOperation` instead of silently returning a true or |
| false value depending on the comparison operator. Quiet NaN values |
| (or ``NaN``) are now hashable. (Fixed by Mark Dickinson; |
| :issue:`7279`.) |
| |
| * The :mod:`difflib` module now produces output that is more |
| compatible with modern :command:`diff`/:command:`patch` tools |
| through one small change, using a tab character instead of spaces as |
| a separator in the header giving the filename. (Fixed by Anatoly |
| Techtonik; :issue:`7585`.) |
| |
| * The Distutils ``sdist`` command now always regenerates the |
| :file:`MANIFEST` file, since even if the :file:`MANIFEST.in` or |
| :file:`setup.py` files haven't been modified, the user might have |
| created some new files that should be included. |
| (Fixed by Tarek Ziadé; :issue:`8688`.) |
| |
| * The :mod:`doctest` module's :const:`IGNORE_EXCEPTION_DETAIL` flag |
| will now ignore the name of the module containing the exception |
| being tested. (Patch by Lennart Regebro; :issue:`7490`.) |
| |
| * The :mod:`email` module's :class:`~email.message.Message` class will |
| now accept a Unicode-valued payload, automatically converting the |
| payload to the encoding specified by :attr:`output_charset`. |
| (Added by R. David Murray; :issue:`1368247`.) |
| |
| * The :class:`~fractions.Fraction` class now accepts a single float or |
| :class:`~decimal.Decimal` instance, or two rational numbers, as |
| arguments to its constructor. (Implemented by Mark Dickinson; |
| rationals added in :issue:`5812`, and float/decimal in |
| :issue:`8294`.) |
| |
| Ordering comparisons (``<``, ``<=``, ``>``, ``>=``) between |
| fractions and complex numbers now raise a :exc:`TypeError`. |
| This fixes an oversight, making the :class:`Fraction` match the other |
| numeric types. |
| |
| .. revision 79455 |
| |
| * New class: :class:`~ftplib.FTP_TLS` in |
| the :mod:`ftplib` module provides secure FTP |
| connections using TLS encapsulation of authentication as well as |
| subsequent control and data transfers. |
| (Contributed by Giampaolo Rodola; :issue:`2054`.) |
| |
| The :meth:`~ftplib.FTP.storbinary` method for binary uploads can now restart |
| uploads thanks to an added *rest* parameter (patch by Pablo Mouzo; |
| :issue:`6845`.) |
| |
| * New class decorator: :func:`total_ordering` in the :mod:`functools` |
| module takes a class that defines an :meth:`__eq__` method and one of |
| :meth:`__lt__`, :meth:`__le__`, :meth:`__gt__`, or :meth:`__ge__`, |
| and generates the missing comparison methods. Since the |
| :meth:`__cmp__` method is being deprecated in Python 3.x, |
| this decorator makes it easier to define ordered classes. |
| (Added by Raymond Hettinger; :issue:`5479`.) |
| |
| New function: :func:`cmp_to_key` will take an old-style comparison |
| function that expects two arguments and return a new callable that |
| can be used as the *key* parameter to functions such as |
| :func:`sorted`, :func:`min` and :func:`max`, etc. The primary |
| intended use is to help with making code compatible with Python 3.x. |
| (Added by Raymond Hettinger.) |
| |
| * New function: the :mod:`gc` module's :func:`~gc.is_tracked` returns |
| true if a given instance is tracked by the garbage collector, false |
| otherwise. (Contributed by Antoine Pitrou; :issue:`4688`.) |
| |
| * The :mod:`gzip` module's :class:`~gzip.GzipFile` now supports the context |
| management protocol, so you can write ``with gzip.GzipFile(...) as f:`` |
| (contributed by Hagen Fürstenau; :issue:`3860`), and it now implements |
| the :class:`io.BufferedIOBase` ABC, so you can wrap it with |
| :class:`io.BufferedReader` for faster processing |
| (contributed by Nir Aides; :issue:`7471`). |
| It's also now possible to override the modification time |
| recorded in a gzipped file by providing an optional timestamp to |
| the constructor. (Contributed by Jacques Frechet; :issue:`4272`.) |
| |
| Files in gzip format can be padded with trailing zero bytes; the |
| :mod:`gzip` module will now consume these trailing bytes. (Fixed by |
| Tadek Pietraszek and Brian Curtin; :issue:`2846`.) |
| |
| * New attribute: the :mod:`hashlib` module now has an :attr:`~hashlib.hashlib.algorithms` |
| attribute containing a tuple naming the supported algorithms. |
| In Python 2.7, ``hashlib.algorithms`` contains |
| ``('md5', 'sha1', 'sha224', 'sha256', 'sha384', 'sha512')``. |
| (Contributed by Carl Chenet; :issue:`7418`.) |
| |
| * The default :class:`~httplib.HTTPResponse` class used by the :mod:`httplib` module now |
| supports buffering, resulting in much faster reading of HTTP responses. |
| (Contributed by Kristján Valur Jónsson; :issue:`4879`.) |
| |
| The :class:`~httplib.HTTPConnection` and :class:`~httplib.HTTPSConnection` classes |
| now support a *source_address* parameter, a ``(host, port)`` 2-tuple |
| giving the source address that will be used for the connection. |
| (Contributed by Eldon Ziegler; :issue:`3972`.) |
| |
| * The :mod:`ihooks` module now supports relative imports. Note that |
| :mod:`ihooks` is an older module for customizing imports, |
| superseded by the :mod:`imputil` module added in Python 2.0. |
| (Relative import support added by Neil Schemenauer.) |
| |
| .. revision 75423 |
| |
| * The :mod:`imaplib` module now supports IPv6 addresses. |
| (Contributed by Derek Morr; :issue:`1655`.) |
| |
| * New function: the :mod:`inspect` module's :func:`~inspect.getcallargs` |
| takes a callable and its positional and keyword arguments, |
| and figures out which of the callable's parameters will receive each argument, |
| returning a dictionary mapping argument names to their values. For example:: |
| |
| >>> from inspect import getcallargs |
| >>> def f(a, b=1, *pos, **named): |
| ... pass |
| >>> getcallargs(f, 1, 2, 3) |
| {'a': 1, 'b': 2, 'pos': (3,), 'named': {}} |
| >>> getcallargs(f, a=2, x=4) |
| {'a': 2, 'b': 1, 'pos': (), 'named': {'x': 4}} |
| >>> getcallargs(f) |
| Traceback (most recent call last): |
| ... |
| TypeError: f() takes at least 1 argument (0 given) |
| |
| Contributed by George Sakkis; :issue:`3135`. |
| |
| * Updated module: The :mod:`io` library has been upgraded to the version shipped with |
| Python 3.1. For 3.1, the I/O library was entirely rewritten in C |
| and is 2 to 20 times faster depending on the task being performed. The |
| original Python version was renamed to the :mod:`_pyio` module. |
| |
| One minor resulting change: the :class:`io.TextIOBase` class now |
| has an :attr:`errors` attribute giving the error setting |
| used for encoding and decoding errors (one of ``'strict'``, ``'replace'``, |
| ``'ignore'``). |
| |
| The :class:`io.FileIO` class now raises an :exc:`OSError` when passed |
| an invalid file descriptor. (Implemented by Benjamin Peterson; |
| :issue:`4991`.) The :meth:`~io.IOBase.truncate` method now preserves the |
| file position; previously it would change the file position to the |
| end of the new file. (Fixed by Pascal Chambon; :issue:`6939`.) |
| |
| * New function: ``itertools.compress(data, selectors)`` takes two |
| iterators. Elements of *data* are returned if the corresponding |
| value in *selectors* is true:: |
| |
| itertools.compress('ABCDEF', [1,0,1,0,1,1]) => |
| A, C, E, F |
| |
| .. maybe here is better to use >>> list(itertools.compress(...)) instead |
| |
| New function: ``itertools.combinations_with_replacement(iter, r)`` |
| returns all the possible *r*-length combinations of elements from the |
| iterable *iter*. Unlike :func:`~itertools.combinations`, individual elements |
| can be repeated in the generated combinations:: |
| |
| itertools.combinations_with_replacement('abc', 2) => |
| ('a', 'a'), ('a', 'b'), ('a', 'c'), |
| ('b', 'b'), ('b', 'c'), ('c', 'c') |
| |
| Note that elements are treated as unique depending on their position |
| in the input, not their actual values. |
| |
| The :func:`itertools.count` function now has a *step* argument that |
| allows incrementing by values other than 1. :func:`~itertools.count` also |
| now allows keyword arguments, and using non-integer values such as |
| floats or :class:`~decimal.Decimal` instances. (Implemented by Raymond |
| Hettinger; :issue:`5032`.) |
| |
| :func:`itertools.combinations` and :func:`itertools.product` |
| previously raised :exc:`ValueError` for values of *r* larger than |
| the input iterable. This was deemed a specification error, so they |
| now return an empty iterator. (Fixed by Raymond Hettinger; :issue:`4816`.) |
| |
| * Updated module: The :mod:`json` module was upgraded to version 2.0.9 of the |
| simplejson package, which includes a C extension that makes |
| encoding and decoding faster. |
| (Contributed by Bob Ippolito; :issue:`4136`.) |
| |
| To support the new :class:`collections.OrderedDict` type, :func:`json.load` |
| now has an optional *object_pairs_hook* parameter that will be called |
| with any object literal that decodes to a list of pairs. |
| (Contributed by Raymond Hettinger; :issue:`5381`.) |
| |
| * The :mod:`mailbox` module's :class:`Maildir` class now records the |
| timestamp on the directories it reads, and only re-reads them if the |
| modification time has subsequently changed. This improves |
| performance by avoiding unneeded directory scans. (Fixed by |
| A.M. Kuchling and Antoine Pitrou; :issue:`1607951`, :issue:`6896`.) |
| |
| * New functions: the :mod:`math` module gained |
| :func:`~math.erf` and :func:`~math.erfc` for the error function and the complementary error function, |
| :func:`~math.expm1` which computes ``e**x - 1`` with more precision than |
| using :func:`~math.exp` and subtracting 1, |
| :func:`~math.gamma` for the Gamma function, and |
| :func:`~math.lgamma` for the natural log of the Gamma function. |
| (Contributed by Mark Dickinson and nirinA raseliarison; :issue:`3366`.) |
| |
| * The :mod:`multiprocessing` module's :class:`Manager*` classes |
| can now be passed a callable that will be called whenever |
| a subprocess is started, along with a set of arguments that will be |
| passed to the callable. |
| (Contributed by lekma; :issue:`5585`.) |
| |
| The :class:`~multiprocessing.Pool` class, which controls a pool of worker processes, |
| now has an optional *maxtasksperchild* parameter. Worker processes |
| will perform the specified number of tasks and then exit, causing the |
| :class:`~multiprocessing.Pool` to start a new worker. This is useful if tasks may leak |
| memory or other resources, or if some tasks will cause the worker to |
| become very large. |
| (Contributed by Charles Cazabon; :issue:`6963`.) |
| |
| * The :mod:`nntplib` module now supports IPv6 addresses. |
| (Contributed by Derek Morr; :issue:`1664`.) |
| |
| * New functions: the :mod:`os` module wraps the following POSIX system |
| calls: :func:`~os.getresgid` and :func:`~os.getresuid`, which return the |
| real, effective, and saved GIDs and UIDs; |
| :func:`~os.setresgid` and :func:`~os.setresuid`, which set |
| real, effective, and saved GIDs and UIDs to new values; |
| :func:`~os.initgroups`, which initialize the group access list |
| for the current process. (GID/UID functions |
| contributed by Travis H.; :issue:`6508`. Support for initgroups added |
| by Jean-Paul Calderone; :issue:`7333`.) |
| |
| The :func:`os.fork` function now re-initializes the import lock in |
| the child process; this fixes problems on Solaris when :func:`~os.fork` |
| is called from a thread. (Fixed by Zsolt Cserna; :issue:`7242`.) |
| |
| * In the :mod:`os.path` module, the :func:`~os.path.normpath` and |
| :func:`~os.path.abspath` functions now preserve Unicode; if their input path |
| is a Unicode string, the return value is also a Unicode string. |
| (:meth:`~os.path.normpath` fixed by Matt Giuca in :issue:`5827`; |
| :meth:`~os.path.abspath` fixed by Ezio Melotti in :issue:`3426`.) |
| |
| * The :mod:`pydoc` module now has help for the various symbols that Python |
| uses. You can now do ``help('<<')`` or ``help('@')``, for example. |
| (Contributed by David Laban; :issue:`4739`.) |
| |
| * The :mod:`re` module's :func:`~re.split`, :func:`~re.sub`, and :func:`~re.subn` |
| now accept an optional *flags* argument, for consistency with the |
| other functions in the module. (Added by Gregory P. Smith.) |
| |
| * New function: :func:`~runpy.run_path` in the :mod:`runpy` module |
| will execute the code at a provided *path* argument. *path* can be |
| the path of a Python source file (:file:`example.py`), a compiled |
| bytecode file (:file:`example.pyc`), a directory |
| (:file:`./package/`), or a zip archive (:file:`example.zip`). If a |
| directory or zip path is provided, it will be added to the front of |
| ``sys.path`` and the module :mod:`__main__` will be imported. It's |
| expected that the directory or zip contains a :file:`__main__.py`; |
| if it doesn't, some other :file:`__main__.py` might be imported from |
| a location later in ``sys.path``. This makes more of the machinery |
| of :mod:`runpy` available to scripts that want to mimic the way |
| Python's command line processes an explicit path name. |
| (Added by Nick Coghlan; :issue:`6816`.) |
| |
| * New function: in the :mod:`shutil` module, :func:`~shutil.make_archive` |
| takes a filename, archive type (zip or tar-format), and a directory |
| path, and creates an archive containing the directory's contents. |
| (Added by Tarek Ziadé.) |
| |
| :mod:`shutil`'s :func:`~shutil.copyfile` and :func:`~shutil.copytree` |
| functions now raise a :exc:`~shutil.SpecialFileError` exception when |
| asked to copy a named pipe. Previously the code would treat |
| named pipes like a regular file by opening them for reading, and |
| this would block indefinitely. (Fixed by Antoine Pitrou; :issue:`3002`.) |
| |
| * The :mod:`signal` module no longer re-installs the signal handler |
| unless this is truly necessary, which fixes a bug that could make it |
| impossible to catch the EINTR signal robustly. (Fixed by |
| Charles-Francois Natali; :issue:`8354`.) |
| |
| * New functions: in the :mod:`site` module, three new functions |
| return various site- and user-specific paths. |
| :func:`~site.getsitepackages` returns a list containing all |
| global site-packages directories, |
| :func:`~site.getusersitepackages` returns the path of the user's |
| site-packages directory, and |
| :func:`~site.getuserbase` returns the value of the :envvar:`USER_BASE` |
| environment variable, giving the path to a directory that can be used |
| to store data. |
| (Contributed by Tarek Ziadé; :issue:`6693`.) |
| |
| The :mod:`site` module now reports exceptions occurring |
| when the :mod:`sitecustomize` module is imported, and will no longer |
| catch and swallow the :exc:`KeyboardInterrupt` exception. (Fixed by |
| Victor Stinner; :issue:`3137`.) |
| |
| * The :func:`~socket.create_connection` function |
| gained a *source_address* parameter, a ``(host, port)`` 2-tuple |
| giving the source address that will be used for the connection. |
| (Contributed by Eldon Ziegler; :issue:`3972`.) |
| |
| The :meth:`~socket.socket.recv_into` and :meth:`~socket.socket.recvfrom_into` |
| methods will now write into objects that support the buffer API, most usefully |
| the :class:`bytearray` and :class:`memoryview` objects. (Implemented by |
| Antoine Pitrou; :issue:`8104`.) |
| |
| * The :mod:`SocketServer` module's :class:`~SocketServer.TCPServer` class now |
| supports socket timeouts and disabling the Nagle algorithm. |
| The :attr:`~SocketServer.TCPServer.disable_nagle_algorithm` class attribute |
| defaults to False; if overridden to be True, |
| new request connections will have the TCP_NODELAY option set to |
| prevent buffering many small sends into a single TCP packet. |
| The :attr:`~SocketServer.TCPServer.timeout` class attribute can hold |
| a timeout in seconds that will be applied to the request socket; if |
| no request is received within that time, :meth:`handle_timeout` |
| will be called and :meth:`handle_request` will return. |
| (Contributed by Kristján Valur Jónsson; :issue:`6192` and :issue:`6267`.) |
| |
| * Updated module: the :mod:`sqlite3` module has been updated to |
| version 2.6.0 of the `pysqlite package <http://code.google.com/p/pysqlite/>`__. Version 2.6.0 includes a number of bugfixes, and adds |
| the ability to load SQLite extensions from shared libraries. |
| Call the ``enable_load_extension(True)`` method to enable extensions, |
| and then call :meth:`~sqlite3.Connection.load_extension` to load a particular shared library. |
| (Updated by Gerhard Häring.) |
| |
| * The :mod:`ssl` module's :class:`ssl.SSLSocket` objects now support the |
| buffer API, which fixed a test suite failure (fix by Antoine Pitrou; |
| :issue:`7133`) and automatically set |
| OpenSSL's :cmacro:`SSL_MODE_AUTO_RETRY`, which will prevent an error |
| code being returned from :meth:`recv` operations that trigger an SSL |
| renegotiation (fix by Antoine Pitrou; :issue:`8222`). |
| |
| The :func:`ssl.wrap_socket` constructor function now takes a |
| *ciphers* argument that's a string listing the encryption algorithms |
| to be allowed; the format of the string is described |
| `in the OpenSSL documentation |
| <http://www.openssl.org/docs/apps/ciphers.html#CIPHER_LIST_FORMAT>`__. |
| (Added by Antoine Pitrou; :issue:`8322`.) |
| |
| Another change makes the extension load all of OpenSSL's ciphers and |
| digest algorithms so that they're all available. Some SSL |
| certificates couldn't be verified, reporting an "unknown algorithm" |
| error. (Reported by Beda Kosata, and fixed by Antoine Pitrou; |
| :issue:`8484`.) |
| |
| The version of OpenSSL being used is now available as the module |
| attributes :data:`ssl.OPENSSL_VERSION` (a string), |
| :data:`ssl.OPENSSL_VERSION_INFO` (a 5-tuple), and |
| :data:`ssl.OPENSSL_VERSION_NUMBER` (an integer). (Added by Antoine |
| Pitrou; :issue:`8321`.) |
| |
| * The :mod:`struct` module will no longer silently ignore overflow |
| errors when a value is too large for a particular integer format |
| code (one of ``bBhHiIlLqQ``); it now always raises a |
| :exc:`struct.error` exception. (Changed by Mark Dickinson; |
| :issue:`1523`.) The :func:`~struct.pack` function will also |
| attempt to use :meth:`__index__` to convert and pack non-integers |
| before trying the :meth:`__int__` method or reporting an error. |
| (Changed by Mark Dickinson; :issue:`8300`.) |
| |
| * New function: the :mod:`subprocess` module's |
| :func:`~subprocess.check_output` runs a command with a specified set of arguments |
| and returns the command's output as a string when the command runs without |
| error, or raises a :exc:`~subprocess.CalledProcessError` exception otherwise. |
| |
| :: |
| |
| >>> subprocess.check_output(['df', '-h', '.']) |
| 'Filesystem Size Used Avail Capacity Mounted on\n |
| /dev/disk0s2 52G 49G 3.0G 94% /\n' |
| |
| >>> subprocess.check_output(['df', '-h', '/bogus']) |
| ... |
| subprocess.CalledProcessError: Command '['df', '-h', '/bogus']' returned non-zero exit status 1 |
| |
| (Contributed by Gregory P. Smith.) |
| |
| The :mod:`subprocess` module will now retry its internal system calls |
| on receiving an :const:`EINTR` signal. (Reported by several people; final |
| patch by Gregory P. Smith in :issue:`1068268`.) |
| |
| * New function: :func:`~symtable.is_declared_global` in the :mod:`symtable` module |
| returns true for variables that are explicitly declared to be global, |
| false for ones that are implicitly global. |
| (Contributed by Jeremy Hylton.) |
| |
| * The :mod:`syslog` module will now use the value of ``sys.argv[0]`` as the |
| identifier instead of the previous default value of ``'python'``. |
| (Changed by Sean Reifschneider; :issue:`8451`.) |
| |
| * The ``sys.version_info`` value is now a named tuple, with attributes |
| named :attr:`major`, :attr:`minor`, :attr:`micro`, |
| :attr:`releaselevel`, and :attr:`serial`. (Contributed by Ross |
| Light; :issue:`4285`.) |
| |
| :func:`sys.getwindowsversion` also returns a named tuple, |
| with attributes named :attr:`major`, :attr:`minor`, :attr:`build`, |
| :attr:`platform`, :attr:`service_pack`, :attr:`service_pack_major`, |
| :attr:`service_pack_minor`, :attr:`suite_mask`, and |
| :attr:`product_type`. (Contributed by Brian Curtin; :issue:`7766`.) |
| |
| * The :mod:`tarfile` module's default error handling has changed, to |
| no longer suppress fatal errors. The default error level was previously 0, |
| which meant that errors would only result in a message being written to the |
| debug log, but because the debug log is not activated by default, |
| these errors go unnoticed. The default error level is now 1, |
| which raises an exception if there's an error. |
| (Changed by Lars Gustäbel; :issue:`7357`.) |
| |
| :mod:`tarfile` now supports filtering the :class:`~tarfile.TarInfo` |
| objects being added to a tar file. When you call :meth:`~tarfile.TarFile.add`, |
| you may supply an optional *filter* argument |
| that's a callable. The *filter* callable will be passed the |
| :class:`~tarfile.TarInfo` for every file being added, and can modify and return it. |
| If the callable returns ``None``, the file will be excluded from the |
| resulting archive. This is more powerful than the existing |
| *exclude* argument, which has therefore been deprecated. |
| (Added by Lars Gustäbel; :issue:`6856`.) |
| The :class:`~tarfile.TarFile` class also now supports the context manager protocol. |
| (Added by Lars Gustäbel; :issue:`7232`.) |
| |
| * The :meth:`~threading.Event.wait` method of the :class:`threading.Event` class |
| now returns the internal flag on exit. This means the method will usually |
| return true because :meth:`~threading.Event.wait` is supposed to block until the |
| internal flag becomes true. The return value will only be false if |
| a timeout was provided and the operation timed out. |
| (Contributed by Tim Lesher; :issue:`1674032`.) |
| |
| * The Unicode database provided by the :mod:`unicodedata` module is |
| now used internally to determine which characters are numeric, |
| whitespace, or represent line breaks. The database also |
| includes information from the :file:`Unihan.txt` data file (patch |
| by Anders Chrigström and Amaury Forgeot d'Arc; :issue:`1571184`) |
| and has been updated to version 5.2.0 (updated by |
| Florent Xicluna; :issue:`8024`). |
| |
| * The :mod:`urlparse` module's :func:`~urlparse.urlsplit` now handles |
| unknown URL schemes in a fashion compliant with :rfc:`3986`: if the |
| URL is of the form ``"<something>://..."``, the text before the |
| ``://`` is treated as the scheme, even if it's a made-up scheme that |
| the module doesn't know about. This change may break code that |
| worked around the old behaviour. For example, Python 2.6.4 or 2.5 |
| will return the following: |
| |
| >>> import urlparse |
| >>> urlparse.urlsplit('invented://host/filename?query') |
| ('invented', '', '//host/filename?query', '', '') |
| |
| Python 2.7 (and Python 2.6.5) will return: |
| |
| >>> import urlparse |
| >>> urlparse.urlsplit('invented://host/filename?query') |
| ('invented', 'host', '/filename?query', '', '') |
| |
| (Python 2.7 actually produces slightly different output, since it |
| returns a named tuple instead of a standard tuple.) |
| |
| The :mod:`urlparse` module also supports IPv6 literal addresses as defined by |
| :rfc:`2732` (contributed by Senthil Kumaran; :issue:`2987`). :: |
| |
| >>> urlparse.urlparse('http://[1080::8:800:200C:417A]/foo') |
| ParseResult(scheme='http', netloc='[1080::8:800:200C:417A]', |
| path='/foo', params='', query='', fragment='') |
| |
| * New class: the :class:`~weakref.WeakSet` class in the :mod:`weakref` |
| module is a set that only holds weak references to its elements; elements |
| will be removed once there are no references pointing to them. |
| (Originally implemented in Python 3.x by Raymond Hettinger, and backported |
| to 2.7 by Michael Foord.) |
| |
| * The ElementTree library, :mod:`xml.etree`, no longer escapes |
| ampersands and angle brackets when outputting an XML processing |
| instruction (which looks like ``<?xml-stylesheet href="#style1"?>``) |
| or comment (which looks like ``<!-- comment -->``). |
| (Patch by Neil Muller; :issue:`2746`.) |
| |
| * The XML-RPC client and server, provided by the :mod:`xmlrpclib` and |
| :mod:`SimpleXMLRPCServer` modules, have improved performance by |
| supporting HTTP/1.1 keep-alive and by optionally using gzip encoding |
| to compress the XML being exchanged. The gzip compression is |
| controlled by the :attr:`encode_threshold` attribute of |
| :class:`SimpleXMLRPCRequestHandler`, which contains a size in bytes; |
| responses larger than this will be compressed. |
| (Contributed by Kristján Valur Jónsson; :issue:`6267`.) |
| |
| * The :mod:`zipfile` module's :class:`~zipfile.ZipFile` now supports the context |
| management protocol, so you can write ``with zipfile.ZipFile(...) as f:``. |
| (Contributed by Brian Curtin; :issue:`5511`.) |
| |
| :mod:`zipfile` now also supports archiving empty directories and |
| extracts them correctly. (Fixed by Kuba Wieczorek; :issue:`4710`.) |
| Reading files out of an archive is faster, and interleaving |
| :meth:`~zipfile.ZipFile.read` and :meth:`~zipfile.ZipFile.readline` now works correctly. |
| (Contributed by Nir Aides; :issue:`7610`.) |
| |
| The :func:`~zipfile.is_zipfile` function now |
| accepts a file object, in addition to the path names accepted in earlier |
| versions. (Contributed by Gabriel Genellina; :issue:`4756`.) |
| |
| The :meth:`~zipfile.ZipFile.writestr` method now has an optional *compress_type* parameter |
| that lets you override the default compression method specified in the |
| :class:`~zipfile.ZipFile` constructor. (Contributed by Ronald Oussoren; |
| :issue:`6003`.) |
| |
| |
| .. ====================================================================== |
| .. whole new modules get described in subsections here |
| |
| |
| .. _importlib-section: |
| |
| New module: importlib |
| ------------------------------ |
| |
| Python 3.1 includes the :mod:`importlib` package, a re-implementation |
| of the logic underlying Python's :keyword:`import` statement. |
| :mod:`importlib` is useful for implementors of Python interpreters and |
| to users who wish to write new importers that can participate in the |
| import process. Python 2.7 doesn't contain the complete |
| :mod:`importlib` package, but instead has a tiny subset that contains |
| a single function, :func:`~importlib.import_module`. |
| |
| ``import_module(name, package=None)`` imports a module. *name* is |
| a string containing the module or package's name. It's possible to do |
| relative imports by providing a string that begins with a ``.`` |
| character, such as ``..utils.errors``. For relative imports, the |
| *package* argument must be provided and is the name of the package that |
| will be used as the anchor for |
| the relative import. :func:`~importlib.import_module` both inserts the imported |
| module into ``sys.modules`` and returns the module object. |
| |
| Here are some examples:: |
| |
| >>> from importlib import import_module |
| >>> anydbm = import_module('anydbm') # Standard absolute import |
| >>> anydbm |
| <module 'anydbm' from '/p/python/Lib/anydbm.py'> |
| >>> # Relative import |
| >>> file_util = import_module('..file_util', 'distutils.command') |
| >>> file_util |
| <module 'distutils.file_util' from '/python/Lib/distutils/file_util.pyc'> |
| |
| :mod:`importlib` was implemented by Brett Cannon and introduced in |
| Python 3.1. |
| |
| |
| New module: sysconfig |
| --------------------------------- |
| |
| The :mod:`sysconfig` module has been pulled out of the Distutils |
| package, becoming a new top-level module in its own right. |
| :mod:`sysconfig` provides functions for getting information about |
| Python's build process: compiler switches, installation paths, the |
| platform name, and whether Python is running from its source |
| directory. |
| |
| Some of the functions in the module are: |
| |
| * :func:`~sysconfig.get_config_var` returns variables from Python's |
| Makefile and the :file:`pyconfig.h` file. |
| * :func:`~sysconfig.get_config_vars` returns a dictionary containing |
| all of the configuration variables. |
| * :func:`~sysconfig.getpath` returns the configured path for |
| a particular type of module: the standard library, |
| site-specific modules, platform-specific modules, etc. |
| * :func:`~sysconfig.is_python_build` returns true if you're running a |
| binary from a Python source tree, and false otherwise. |
| |
| Consult the :mod:`sysconfig` documentation for more details and for |
| a complete list of functions. |
| |
| The Distutils package and :mod:`sysconfig` are now maintained by Tarek |
| Ziadé, who has also started a Distutils2 package (source repository at |
| http://hg.python.org/distutils2/) for developing a next-generation |
| version of Distutils. |
| |
| |
| ttk: Themed Widgets for Tk |
| -------------------------- |
| |
| Tcl/Tk 8.5 includes a set of themed widgets that re-implement basic Tk |
| widgets but have a more customizable appearance and can therefore more |
| closely resemble the native platform's widgets. This widget |
| set was originally called Tile, but was renamed to Ttk (for "themed Tk") |
| on being added to Tcl/Tck release 8.5. |
| |
| To learn more, read the :mod:`ttk` module documentation. You may also |
| wish to read the Tcl/Tk manual page describing the |
| Ttk theme engine, available at |
| http://www.tcl.tk/man/tcl8.5/TkCmd/ttk_intro.htm. Some |
| screenshots of the Python/Ttk code in use are at |
| http://code.google.com/p/python-ttk/wiki/Screenshots. |
| |
| The :mod:`ttk` module was written by Guilherme Polo and added in |
| :issue:`2983`. An alternate version called ``Tile.py``, written by |
| Martin Franklin and maintained by Kevin Walzer, was proposed for |
| inclusion in :issue:`2618`, but the authors argued that Guilherme |
| Polo's work was more comprehensive. |
| |
| |
| .. _unittest-section: |
| |
| Updated module: unittest |
| --------------------------------- |
| |
| The :mod:`unittest` module was greatly enhanced; many |
| new features were added. Most of these features were implemented |
| by Michael Foord, unless otherwise noted. The enhanced version of |
| the module is downloadable separately for use with Python versions 2.4 to 2.6, |
| packaged as the :mod:`unittest2` package, from |
| http://pypi.python.org/pypi/unittest2. |
| |
| When used from the command line, the module can automatically discover |
| tests. It's not as fancy as `py.test <http://pytest.org>`__ or |
| `nose <http://code.google.com/p/python-nose/>`__, but provides a simple way |
| to run tests kept within a set of package directories. For example, |
| the following command will search the :file:`test/` subdirectory for |
| any importable test files named ``test*.py``:: |
| |
| python -m unittest discover -s test |
| |
| Consult the :mod:`unittest` module documentation for more details. |
| (Developed in :issue:`6001`.) |
| |
| The :func:`main` function supports some other new options: |
| |
| * :option:`-b` or :option:`--buffer` will buffer the standard output |
| and standard error streams during each test. If the test passes, |
| any resulting output will be discarded; on failure, the buffered |
| output will be displayed. |
| |
| * :option:`-c` or :option:`--catch` will cause the control-C interrupt |
| to be handled more gracefully. Instead of interrupting the test |
| process immediately, the currently running test will be completed |
| and then the partial results up to the interruption will be reported. |
| If you're impatient, a second press of control-C will cause an immediate |
| interruption. |
| |
| This control-C handler tries to avoid causing problems when the code |
| being tested or the tests being run have defined a signal handler of |
| their own, by noticing that a signal handler was already set and |
| calling it. If this doesn't work for you, there's a |
| :func:`removeHandler` decorator that can be used to mark tests that |
| should have the control-C handling disabled. |
| |
| * :option:`-f` or :option:`--failfast` makes |
| test execution stop immediately when a test fails instead of |
| continuing to execute further tests. (Suggested by Cliff Dyer and |
| implemented by Michael Foord; :issue:`8074`.) |
| |
| The progress messages now show 'x' for expected failures |
| and 'u' for unexpected successes when run in verbose mode. |
| (Contributed by Benjamin Peterson.) |
| |
| Test cases can raise the :exc:`~unittest.SkipTest` exception to skip a |
| test (:issue:`1034053`). |
| |
| The error messages for :meth:`~unittest.TestCase.assertEqual`, |
| :meth:`~unittest.TestCase.assertTrue`, and :meth:`~unittest.TestCase.assertFalse` |
| failures now provide more information. If you set the |
| :attr:`~unittest.TestCase.longMessage` attribute of your :class:`~unittest.TestCase` classes to |
| True, both the standard error message and any additional message you |
| provide will be printed for failures. (Added by Michael Foord; :issue:`5663`.) |
| |
| The :meth:`~unittest.TestCase.assertRaises` method now |
| returns a context handler when called without providing a callable |
| object to run. For example, you can write this:: |
| |
| with self.assertRaises(KeyError): |
| {}['foo'] |
| |
| (Implemented by Antoine Pitrou; :issue:`4444`.) |
| |
| .. rev 78774 |
| |
| Module- and class-level setup and teardown fixtures are now supported. |
| Modules can contain :func:`~unittest.setUpModule` and :func:`~unittest.tearDownModule` |
| functions. Classes can have :meth:`~unittest.TestCase.setUpClass` and |
| :meth:`~unittest.TestCase.tearDownClass` methods that must be defined as class methods |
| (using ``@classmethod`` or equivalent). These functions and |
| methods are invoked when the test runner switches to a test case in a |
| different module or class. |
| |
| The methods :meth:`~unittest.TestCase.addCleanup` and |
| :meth:`~unittest.TestCase.doCleanups` were added. |
| :meth:`~unittest.TestCase.addCleanup` lets you add cleanup functions that |
| will be called unconditionally (after :meth:`~unittest.TestCase.setUp` if |
| :meth:`~unittest.TestCase.setUp` fails, otherwise after :meth:`~unittest.TestCase.tearDown`). This allows |
| for much simpler resource allocation and deallocation during tests |
| (:issue:`5679`). |
| |
| A number of new methods were added that provide more specialized |
| tests. Many of these methods were written by Google engineers |
| for use in their test suites; Gregory P. Smith, Michael Foord, and |
| GvR worked on merging them into Python's version of :mod:`unittest`. |
| |
| * :meth:`~unittest.TestCase.assertIsNone` and :meth:`~unittest.TestCase.assertIsNotNone` take one |
| expression and verify that the result is or is not ``None``. |
| |
| * :meth:`~unittest.TestCase.assertIs` and :meth:`~unittest.TestCase.assertIsNot` |
| take two values and check whether the two values evaluate to the same object or not. |
| (Added by Michael Foord; :issue:`2578`.) |
| |
| * :meth:`~unittest.TestCase.assertIsInstance` and |
| :meth:`~unittest.TestCase.assertNotIsInstance` check whether |
| the resulting object is an instance of a particular class, or of |
| one of a tuple of classes. (Added by Georg Brandl; :issue:`7031`.) |
| |
| * :meth:`~unittest.TestCase.assertGreater`, :meth:`~unittest.TestCase.assertGreaterEqual`, |
| :meth:`~unittest.TestCase.assertLess`, and :meth:`~unittest.TestCase.assertLessEqual` compare |
| two quantities. |
| |
| * :meth:`~unittest.TestCase.assertMultiLineEqual` compares two strings, and if they're |
| not equal, displays a helpful comparison that highlights the |
| differences in the two strings. This comparison is now used by |
| default when Unicode strings are compared with :meth:`~unittest.TestCase.assertEqual`. |
| |
| * :meth:`~unittest.TestCase.assertRegexpMatches` and |
| :meth:`~unittest.TestCase.assertNotRegexpMatches` checks whether the |
| first argument is a string matching or not matching the regular |
| expression provided as the second argument (:issue:`8038`). |
| |
| * :meth:`~unittest.TestCase.assertRaisesRegexp` checks whether a particular exception |
| is raised, and then also checks that the string representation of |
| the exception matches the provided regular expression. |
| |
| * :meth:`~unittest.TestCase.assertIn` and :meth:`~unittest.TestCase.assertNotIn` |
| tests whether *first* is or is not in *second*. |
| |
| * :meth:`~unittest.TestCase.assertItemsEqual` tests whether two provided sequences |
| contain the same elements. |
| |
| * :meth:`~unittest.TestCase.assertSetEqual` compares whether two sets are equal, and |
| only reports the differences between the sets in case of error. |
| |
| * Similarly, :meth:`~unittest.TestCase.assertListEqual` and :meth:`~unittest.TestCase.assertTupleEqual` |
| compare the specified types and explain any differences without necessarily |
| printing their full values; these methods are now used by default |
| when comparing lists and tuples using :meth:`~unittest.TestCase.assertEqual`. |
| More generally, :meth:`~unittest.TestCase.assertSequenceEqual` compares two sequences |
| and can optionally check whether both sequences are of a |
| particular type. |
| |
| * :meth:`~unittest.TestCase.assertDictEqual` compares two dictionaries and reports the |
| differences; it's now used by default when you compare two dictionaries |
| using :meth:`~unittest.TestCase.assertEqual`. :meth:`~unittest.TestCase.assertDictContainsSubset` checks whether |
| all of the key/value pairs in *first* are found in *second*. |
| |
| * :meth:`~unittest.TestCase.assertAlmostEqual` and :meth:`~unittest.TestCase.assertNotAlmostEqual` test |
| whether *first* and *second* are approximately equal. This method |
| can either round their difference to an optionally-specified number |
| of *places* (the default is 7) and compare it to zero, or require |
| the difference to be smaller than a supplied *delta* value. |
| |
| * :meth:`~unittest.TestLoader.loadTestsFromName` properly honors the |
| :attr:`~unittest.TestLoader.suiteClass` attribute of |
| the :class:`~unittest.TestLoader`. (Fixed by Mark Roddy; :issue:`6866`.) |
| |
| * A new hook lets you extend the :meth:`~unittest.TestCase.assertEqual` method to handle |
| new data types. The :meth:`~unittest.TestCase.addTypeEqualityFunc` method takes a type |
| object and a function. The function will be used when both of the |
| objects being compared are of the specified type. This function |
| should compare the two objects and raise an exception if they don't |
| match; it's a good idea for the function to provide additional |
| information about why the two objects aren't matching, much as the new |
| sequence comparison methods do. |
| |
| :func:`unittest.main` now takes an optional ``exit`` argument. If |
| False, :func:`~unittest.main` doesn't call :func:`sys.exit`, allowing |
| :func:`main` to be used from the interactive interpreter. |
| (Contributed by J. Pablo Fernández; :issue:`3379`.) |
| |
| :class:`~unittest.TestResult` has new :meth:`~unittest.TestResult.startTestRun` and |
| :meth:`~unittest.TestResult.stopTestRun` methods that are called immediately before |
| and after a test run. (Contributed by Robert Collins; :issue:`5728`.) |
| |
| With all these changes, the :file:`unittest.py` was becoming awkwardly |
| large, so the module was turned into a package and the code split into |
| several files (by Benjamin Peterson). This doesn't affect how the |
| module is imported or used. |
| |
| .. seealso:: |
| |
| http://www.voidspace.org.uk/python/articles/unittest2.shtml |
| Describes the new features, how to use them, and the |
| rationale for various design decisions. (By Michael Foord.) |
| |
| .. _elementtree-section: |
| |
| Updated module: ElementTree 1.3 |
| --------------------------------- |
| |
| The version of the ElementTree library included with Python was updated to |
| version 1.3. Some of the new features are: |
| |
| * The various parsing functions now take a *parser* keyword argument |
| giving an :class:`XMLParser` instance that will |
| be used. This makes it possible to override the file's internal encoding:: |
| |
| p = ET.XMLParser(encoding='utf-8') |
| t = ET.XML("""<root/>""", parser=p) |
| |
| Errors in parsing XML now raise a :exc:`ParseError` exception, whose |
| instances have a :attr:`position` attribute |
| containing a (*line*, *column*) tuple giving the location of the problem. |
| |
| * ElementTree's code for converting trees to a string has been |
| significantly reworked, making it roughly twice as fast in many |
| cases. The :class:`ElementTree` :meth:`write` and :class:`Element` |
| :meth:`write` methods now have a *method* parameter that can be |
| "xml" (the default), "html", or "text". HTML mode will output empty |
| elements as ``<empty></empty>`` instead of ``<empty/>``, and text |
| mode will skip over elements and only output the text chunks. If |
| you set the :attr:`tag` attribute of an element to ``None`` but |
| leave its children in place, the element will be omitted when the |
| tree is written out, so you don't need to do more extensive rearrangement |
| to remove a single element. |
| |
| Namespace handling has also been improved. All ``xmlns:<whatever>`` |
| declarations are now output on the root element, not scattered throughout |
| the resulting XML. You can set the default namespace for a tree |
| by setting the :attr:`default_namespace` attribute and can |
| register new prefixes with :meth:`register_namespace`. In XML mode, |
| you can use the true/false *xml_declaration* parameter to suppress the |
| XML declaration. |
| |
| * New :class:`Element` method: :meth:`extend` appends the items from a |
| sequence to the element's children. Elements themselves behave like |
| sequences, so it's easy to move children from one element to |
| another:: |
| |
| from xml.etree import ElementTree as ET |
| |
| t = ET.XML("""<list> |
| <item>1</item> <item>2</item> <item>3</item> |
| </list>""") |
| new = ET.XML('<root/>') |
| new.extend(t) |
| |
| # Outputs <root><item>1</item>...</root> |
| print ET.tostring(new) |
| |
| * New :class:`Element` method: :meth:`iter` yields the children of the |
| element as a generator. It's also possible to write ``for child in |
| elem:`` to loop over an element's children. The existing method |
| :meth:`getiterator` is now deprecated, as is :meth:`getchildren` |
| which constructs and returns a list of children. |
| |
| * New :class:`Element` method: :meth:`itertext` yields all chunks of |
| text that are descendants of the element. For example:: |
| |
| t = ET.XML("""<list> |
| <item>1</item> <item>2</item> <item>3</item> |
| </list>""") |
| |
| # Outputs ['\n ', '1', ' ', '2', ' ', '3', '\n'] |
| print list(t.itertext()) |
| |
| * Deprecated: using an element as a Boolean (i.e., ``if elem:``) would |
| return true if the element had any children, or false if there were |
| no children. This behaviour is confusing -- ``None`` is false, but |
| so is a childless element? -- so it will now trigger a |
| :exc:`FutureWarning`. In your code, you should be explicit: write |
| ``len(elem) != 0`` if you're interested in the number of children, |
| or ``elem is not None``. |
| |
| Fredrik Lundh develops ElementTree and produced the 1.3 version; |
| you can read his article describing 1.3 at |
| http://effbot.org/zone/elementtree-13-intro.htm. |
| Florent Xicluna updated the version included with |
| Python, after discussions on python-dev and in :issue:`6472`.) |
| |
| .. ====================================================================== |
| |
| |
| Build and C API Changes |
| ======================= |
| |
| Changes to Python's build process and to the C API include: |
| |
| * The latest release of the GNU Debugger, GDB 7, can be `scripted |
| using Python |
| <http://sourceware.org/gdb/current/onlinedocs/gdb/Python.html>`__. |
| When you begin debugging an executable program P, GDB will look for |
| a file named ``P-gdb.py`` and automatically read it. Dave Malcolm |
| contributed a :file:`python-gdb.py` that adds a number of |
| commands useful when debugging Python itself. For example, |
| ``py-up`` and ``py-down`` go up or down one Python stack frame, |
| which usually corresponds to several C stack frames. ``py-print`` |
| prints the value of a Python variable, and ``py-bt`` prints the |
| Python stack trace. (Added as a result of :issue:`8032`.) |
| |
| * If you use the :file:`.gdbinit` file provided with Python, |
| the "pyo" macro in the 2.7 version now works correctly when the thread being |
| debugged doesn't hold the GIL; the macro now acquires it before printing. |
| (Contributed by Victor Stinner; :issue:`3632`.) |
| |
| * :cfunc:`Py_AddPendingCall` is now thread-safe, letting any |
| worker thread submit notifications to the main Python thread. This |
| is particularly useful for asynchronous IO operations. |
| (Contributed by Kristján Valur Jónsson; :issue:`4293`.) |
| |
| * New function: :cfunc:`PyCode_NewEmpty` creates an empty code object; |
| only the filename, function name, and first line number are required. |
| This is useful for extension modules that are attempting to |
| construct a more useful traceback stack. Previously such |
| extensions needed to call :cfunc:`PyCode_New`, which had many |
| more arguments. (Added by Jeffrey Yasskin.) |
| |
| * New function: :cfunc:`PyErr_NewExceptionWithDoc` creates a new |
| exception class, just as the existing :cfunc:`PyErr_NewException` does, |
| but takes an extra ``char *`` argument containing the docstring for the |
| new exception class. (Added by 'lekma' on the Python bug tracker; |
| :issue:`7033`.) |
| |
| * New function: :cfunc:`PyFrame_GetLineNumber` takes a frame object |
| and returns the line number that the frame is currently executing. |
| Previously code would need to get the index of the bytecode |
| instruction currently executing, and then look up the line number |
| corresponding to that address. (Added by Jeffrey Yasskin.) |
| |
| * New functions: :cfunc:`PyLong_AsLongAndOverflow` and |
| :cfunc:`PyLong_AsLongLongAndOverflow` approximates a Python long |
| integer as a C :ctype:`long` or :ctype:`long long`. |
| If the number is too large to fit into |
| the output type, an *overflow* flag is set and returned to the caller. |
| (Contributed by Case Van Horsen; :issue:`7528` and :issue:`7767`.) |
| |
| * New function: stemming from the rewrite of string-to-float conversion, |
| a new :cfunc:`PyOS_string_to_double` function was added. The old |
| :cfunc:`PyOS_ascii_strtod` and :cfunc:`PyOS_ascii_atof` functions |
| are now deprecated. |
| |
| * New function: :cfunc:`PySys_SetArgvEx` sets the value of |
| ``sys.argv`` and can optionally update ``sys.path`` to include the |
| directory containing the script named by ``sys.argv[0]`` depending |
| on the value of an *updatepath* parameter. |
| |
| This function was added to close a security hole for applications |
| that embed Python. The old function, :cfunc:`PySys_SetArgv`, would |
| always update ``sys.path``, and sometimes it would add the current |
| directory. This meant that, if you ran an application embedding |
| Python in a directory controlled by someone else, attackers could |
| put a Trojan-horse module in the directory (say, a file named |
| :file:`os.py`) that your application would then import and run. |
| |
| If you maintain a C/C++ application that embeds Python, check |
| whether you're calling :cfunc:`PySys_SetArgv` and carefully consider |
| whether the application should be using :cfunc:`PySys_SetArgvEx` |
| with *updatepath* set to false. |
| |
| Security issue reported as `CVE-2008-5983 |
| <http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2008-5983>`_; |
| discussed in :issue:`5753`, and fixed by Antoine Pitrou. |
| |
| * New macros: the Python header files now define the following macros: |
| :cmacro:`Py_ISALNUM`, |
| :cmacro:`Py_ISALPHA`, |
| :cmacro:`Py_ISDIGIT`, |
| :cmacro:`Py_ISLOWER`, |
| :cmacro:`Py_ISSPACE`, |
| :cmacro:`Py_ISUPPER`, |
| :cmacro:`Py_ISXDIGIT`, |
| and :cmacro:`Py_TOLOWER`, :cmacro:`Py_TOUPPER`. |
| All of these functions are analogous to the C |
| standard macros for classifying characters, but ignore the current |
| locale setting, because in |
| several places Python needs to analyze characters in a |
| locale-independent way. (Added by Eric Smith; |
| :issue:`5793`.) |
| |
| .. XXX these macros don't seem to be described in the c-api docs. |
| |
| * Removed function: :cmacro:`PyEval_CallObject` is now only available |
| as a macro. A function version was being kept around to preserve |
| ABI linking compatibility, but that was in 1997; it can certainly be |
| deleted by now. (Removed by Antoine Pitrou; :issue:`8276`.) |
| |
| * New format codes: the :cfunc:`PyFormat_FromString`, |
| :cfunc:`PyFormat_FromStringV`, and :cfunc:`PyErr_Format` functions now |
| accept ``%lld`` and ``%llu`` format codes for displaying |
| C's :ctype:`long long` types. |
| (Contributed by Mark Dickinson; :issue:`7228`.) |
| |
| * The complicated interaction between threads and process forking has |
| been changed. Previously, the child process created by |
| :func:`os.fork` might fail because the child is created with only a |
| single thread running, the thread performing the :func:`os.fork`. |
| If other threads were holding a lock, such as Python's import lock, |
| when the fork was performed, the lock would still be marked as |
| "held" in the new process. But in the child process nothing would |
| ever release the lock, since the other threads weren't replicated, |
| and the child process would no longer be able to perform imports. |
| |
| Python 2.7 acquires the import lock before performing an |
| :func:`os.fork`, and will also clean up any locks created using the |
| :mod:`threading` module. C extension modules that have internal |
| locks, or that call :cfunc:`fork()` themselves, will not benefit |
| from this clean-up. |
| |
| (Fixed by Thomas Wouters; :issue:`1590864`.) |
| |
| * The :cfunc:`Py_Finalize` function now calls the internal |
| :func:`threading._shutdown` function; this prevents some exceptions from |
| being raised when an interpreter shuts down. |
| (Patch by Adam Olsen; :issue:`1722344`.) |
| |
| * When using the :ctype:`PyMemberDef` structure to define attributes |
| of a type, Python will no longer let you try to delete or set a |
| :const:`T_STRING_INPLACE` attribute. |
| |
| .. rev 79644 |
| |
| * Global symbols defined by the :mod:`ctypes` module are now prefixed |
| with ``Py``, or with ``_ctypes``. (Implemented by Thomas |
| Heller; :issue:`3102`.) |
| |
| * New configure option: the :option:`--with-system-expat` switch allows |
| building the :mod:`pyexpat` module to use the system Expat library. |
| (Contributed by Arfrever Frehtes Taifersar Arahesis; :issue:`7609`.) |
| |
| * New configure option: the |
| :option:`--with-valgrind` option will now disable the pymalloc |
| allocator, which is difficult for the Valgrind memory-error detector |
| to analyze correctly. |
| Valgrind will therefore be better at detecting memory leaks and |
| overruns. (Contributed by James Henstridge; :issue:`2422`.) |
| |
| * New configure option: you can now supply an empty string to |
| :option:`--with-dbmliborder=` in order to disable all of the various |
| DBM modules. (Added by Arfrever Frehtes Taifersar Arahesis; |
| :issue:`6491`.) |
| |
| * The :program:`configure` script now checks for floating-point rounding bugs |
| on certain 32-bit Intel chips and defines a :cmacro:`X87_DOUBLE_ROUNDING` |
| preprocessor definition. No code currently uses this definition, |
| but it's available if anyone wishes to use it. |
| (Added by Mark Dickinson; :issue:`2937`.) |
| |
| :program:`configure` also now sets a :envvar:`LDCXXSHARED` Makefile |
| variable for supporting C++ linking. (Contributed by Arfrever |
| Frehtes Taifersar Arahesis; :issue:`1222585`.) |
| |
| * The build process now creates the necessary files for pkg-config |
| support. (Contributed by Clinton Roy; :issue:`3585`.) |
| |
| * The build process now supports Subversion 1.7. (Contributed by |
| Arfrever Frehtes Taifersar Arahesis; :issue:`6094`.) |
| |
| |
| .. _whatsnew27-capsules: |
| |
| Capsules |
| ------------------- |
| |
| Python 3.1 adds a new C datatype, :ctype:`PyCapsule`, for providing a |
| C API to an extension module. A capsule is essentially the holder of |
| a C ``void *`` pointer, and is made available as a module attribute; for |
| example, the :mod:`socket` module's API is exposed as ``socket.CAPI``, |
| and :mod:`unicodedata` exposes ``ucnhash_CAPI``. Other extensions |
| can import the module, access its dictionary to get the capsule |
| object, and then get the ``void *`` pointer, which will usually point |
| to an array of pointers to the module's various API functions. |
| |
| There is an existing data type already used for this, |
| :ctype:`PyCObject`, but it doesn't provide type safety. Evil code |
| written in pure Python could cause a segmentation fault by taking a |
| :ctype:`PyCObject` from module A and somehow substituting it for the |
| :ctype:`PyCObject` in module B. Capsules know their own name, |
| and getting the pointer requires providing the name:: |
| |
| void *vtable; |
| |
| if (!PyCapsule_IsValid(capsule, "mymodule.CAPI") { |
| PyErr_SetString(PyExc_ValueError, "argument type invalid"); |
| return NULL; |
| } |
| |
| vtable = PyCapsule_GetPointer(capsule, "mymodule.CAPI"); |
| |
| You are assured that ``vtable`` points to whatever you're expecting. |
| If a different capsule was passed in, :cfunc:`PyCapsule_IsValid` would |
| detect the mismatched name and return false. Refer to |
| :ref:`using-capsules` for more information on using these objects. |
| |
| Python 2.7 now uses capsules internally to provide various |
| extension-module APIs, but the :cfunc:`PyCObject_AsVoidPtr` was |
| modified to handle capsules, preserving compile-time compatibility |
| with the :ctype:`CObject` interface. Use of |
| :cfunc:`PyCObject_AsVoidPtr` will signal a |
| :exc:`PendingDeprecationWarning`, which is silent by default. |
| |
| Implemented in Python 3.1 and backported to 2.7 by Larry Hastings; |
| discussed in :issue:`5630`. |
| |
| |
| .. ====================================================================== |
| |
| Port-Specific Changes: Windows |
| ----------------------------------- |
| |
| * The :mod:`msvcrt` module now contains some constants from |
| the :file:`crtassem.h` header file: |
| :data:`CRT_ASSEMBLY_VERSION`, |
| :data:`VC_ASSEMBLY_PUBLICKEYTOKEN`, |
| and :data:`LIBRARIES_ASSEMBLY_NAME_PREFIX`. |
| (Contributed by David Cournapeau; :issue:`4365`.) |
| |
| * The :mod:`_winreg` module for accessing the registry now implements |
| the :func:`CreateKeyEx` and :func:`DeleteKeyEx` functions, extended |
| versions of previously-supported functions that take several extra |
| arguments. The :func:`DisableReflectionKey`, |
| :func:`EnableReflectionKey`, and :func:`QueryReflectionKey` were also |
| tested and documented. |
| (Implemented by Brian Curtin: :issue:`7347`.) |
| |
| * The new :cfunc:`_beginthreadex` API is used to start threads, and |
| the native thread-local storage functions are now used. |
| (Contributed by Kristján Valur Jónsson; :issue:`3582`.) |
| |
| * The :func:`os.kill` function now works on Windows. The signal value |
| can be the constants :const:`CTRL_C_EVENT`, |
| :const:`CTRL_BREAK_EVENT`, or any integer. The first two constants |
| will send Control-C and Control-Break keystroke events to |
| subprocesses; any other value will use the :cfunc:`TerminateProcess` |
| API. (Contributed by Miki Tebeka; :issue:`1220212`.) |
| |
| * The :func:`os.listdir` function now correctly fails |
| for an empty path. (Fixed by Hirokazu Yamamoto; :issue:`5913`.) |
| |
| * The :mod:`mimelib` module will now read the MIME database from |
| the Windows registry when initializing. |
| (Patch by Gabriel Genellina; :issue:`4969`.) |
| |
| .. ====================================================================== |
| |
| Port-Specific Changes: Mac OS X |
| ----------------------------------- |
| |
| * The path ``/Library/Python/2.7/site-packages`` is now appended to |
| ``sys.path``, in order to share added packages between the system |
| installation and a user-installed copy of the same version. |
| (Changed by Ronald Oussoren; :issue:`4865`.) |
| |
| Port-Specific Changes: FreeBSD |
| ----------------------------------- |
| |
| * FreeBSD 7.1's :const:`SO_SETFIB` constant, used with |
| :func:`~socket.getsockopt`/:func:`~socket.setsockopt` to select an |
| alternate routing table, is now available in the :mod:`socket` |
| module. (Added by Kyle VanderBeek; :issue:`8235`.) |
| |
| Other Changes and Fixes |
| ======================= |
| |
| * Two benchmark scripts, :file:`iobench` and :file:`ccbench`, were |
| added to the :file:`Tools` directory. :file:`iobench` measures the |
| speed of the built-in file I/O objects returned by :func:`open` |
| while performing various operations, and :file:`ccbench` is a |
| concurrency benchmark that tries to measure computing throughput, |
| thread switching latency, and IO processing bandwidth when |
| performing several tasks using a varying number of threads. |
| |
| * The :file:`Tools/i18n/msgfmt.py` script now understands plural |
| forms in :file:`.po` files. (Fixed by Martin von Löwis; |
| :issue:`5464`.) |
| |
| * When importing a module from a :file:`.pyc` or :file:`.pyo` file |
| with an existing :file:`.py` counterpart, the :attr:`co_filename` |
| attributes of the resulting code objects are overwritten when the |
| original filename is obsolete. This can happen if the file has been |
| renamed, moved, or is accessed through different paths. (Patch by |
| Ziga Seilnacht and Jean-Paul Calderone; :issue:`1180193`.) |
| |
| * The :file:`regrtest.py` script now takes a :option:`--randseed=` |
| switch that takes an integer that will be used as the random seed |
| for the :option:`-r` option that executes tests in random order. |
| The :option:`-r` option also reports the seed that was used |
| (Added by Collin Winter.) |
| |
| * Another :file:`regrtest.py` switch is :option:`-j`, which |
| takes an integer specifying how many tests run in parallel. This |
| allows reducing the total runtime on multi-core machines. |
| This option is compatible with several other options, including the |
| :option:`-R` switch which is known to produce long runtimes. |
| (Added by Antoine Pitrou, :issue:`6152`.) This can also be used |
| with a new :option:`-F` switch that runs selected tests in a loop |
| until they fail. (Added by Antoine Pitrou; :issue:`7312`.) |
| |
| * When executed as a script, the :file:`py_compile.py` module now |
| accepts ``'-'`` as an argument, which will read standard input for |
| the list of filenames to be compiled. (Contributed by Piotr |
| Ożarowski; :issue:`8233`.) |
| |
| .. ====================================================================== |
| |
| Porting to Python 2.7 |
| ===================== |
| |
| This section lists previously described changes and other bugfixes |
| that may require changes to your code: |
| |
| * The :func:`range` function processes its arguments more |
| consistently; it will now call :meth:`__int__` on non-float, |
| non-integer arguments that are supplied to it. (Fixed by Alexander |
| Belopolsky; :issue:`1533`.) |
| |
| * The string :meth:`format` method changed the default precision used |
| for floating-point and complex numbers from 6 decimal |
| places to 12, which matches the precision used by :func:`str`. |
| (Changed by Eric Smith; :issue:`5920`.) |
| |
| * Because of an optimization for the :keyword:`with` statement, the special |
| methods :meth:`__enter__` and :meth:`__exit__` must belong to the object's |
| type, and cannot be directly attached to the object's instance. This |
| affects new-style classes (derived from :class:`object`) and C extension |
| types. (:issue:`6101`.) |
| |
| * Due to a bug in Python 2.6, the *exc_value* parameter to |
| :meth:`__exit__` methods was often the string representation of the |
| exception, not an instance. This was fixed in 2.7, so *exc_value* |
| will be an instance as expected. (Fixed by Florent Xicluna; |
| :issue:`7853`.) |
| |
| * When a restricted set of attributes were set using ``__slots__``, |
| deleting an unset attribute would not raise :exc:`AttributeError` |
| as you would expect. Fixed by Benjamin Peterson; :issue:`7604`.) |
| |
| In the standard library: |
| |
| * Operations with :class:`datetime` instances that resulted in a year |
| falling outside the supported range didn't always raise |
| :exc:`OverflowError`. Such errors are now checked more carefully |
| and will now raise the exception. (Reported by Mark Leander, patch |
| by Anand B. Pillai and Alexander Belopolsky; :issue:`7150`.) |
| |
| * When using :class:`Decimal` instances with a string's |
| :meth:`format` method, the default alignment was previously |
| left-alignment. This has been changed to right-alignment, which might |
| change the output of your programs. |
| (Changed by Mark Dickinson; :issue:`6857`.) |
| |
| Comparisons involving a signaling NaN value (or ``sNAN``) now signal |
| :const:`InvalidOperation` instead of silently returning a true or |
| false value depending on the comparison operator. Quiet NaN values |
| (or ``NaN``) are now hashable. (Fixed by Mark Dickinson; |
| :issue:`7279`.) |
| |
| * The ElementTree library, :mod:`xml.etree`, no longer escapes |
| ampersands and angle brackets when outputting an XML processing |
| instruction (which looks like `<?xml-stylesheet href="#style1"?>`) |
| or comment (which looks like `<!-- comment -->`). |
| (Patch by Neil Muller; :issue:`2746`.) |
| |
| * The :meth:`readline` method of :class:`StringIO` objects now does |
| nothing when a negative length is requested, as other file-like |
| objects do. (:issue:`7348`). |
| |
| * The :mod:`syslog` module will now use the value of ``sys.argv[0]`` as the |
| identifier instead of the previous default value of ``'python'``. |
| (Changed by Sean Reifschneider; :issue:`8451`.) |
| |
| * The :mod:`tarfile` module's default error handling has changed, to |
| no longer suppress fatal errors. The default error level was previously 0, |
| which meant that errors would only result in a message being written to the |
| debug log, but because the debug log is not activated by default, |
| these errors go unnoticed. The default error level is now 1, |
| which raises an exception if there's an error. |
| (Changed by Lars Gustäbel; :issue:`7357`.) |
| |
| * The :mod:`urlparse` module's :func:`~urlparse.urlsplit` now handles |
| unknown URL schemes in a fashion compliant with :rfc:`3986`: if the |
| URL is of the form ``"<something>://..."``, the text before the |
| ``://`` is treated as the scheme, even if it's a made-up scheme that |
| the module doesn't know about. This change may break code that |
| worked around the old behaviour. For example, Python 2.6.4 or 2.5 |
| will return the following: |
| |
| >>> import urlparse |
| >>> urlparse.urlsplit('invented://host/filename?query') |
| ('invented', '', '//host/filename?query', '', '') |
| |
| Python 2.7 (and Python 2.6.5) will return: |
| |
| >>> import urlparse |
| >>> urlparse.urlsplit('invented://host/filename?query') |
| ('invented', 'host', '/filename?query', '', '') |
| |
| (Python 2.7 actually produces slightly different output, since it |
| returns a named tuple instead of a standard tuple.) |
| |
| For C extensions: |
| |
| * C extensions that use integer format codes with the ``PyArg_Parse*`` |
| family of functions will now raise a :exc:`TypeError` exception |
| instead of triggering a :exc:`DeprecationWarning` (:issue:`5080`). |
| |
| * Use the new :cfunc:`PyOS_string_to_double` function instead of the old |
| :cfunc:`PyOS_ascii_strtod` and :cfunc:`PyOS_ascii_atof` functions, |
| which are now deprecated. |
| |
| For applications that embed Python: |
| |
| * The :cfunc:`PySys_SetArgvEx` function was added, letting |
| applications close a security hole when the existing |
| :cfunc:`PySys_SetArgv` function was used. Check whether you're |
| calling :cfunc:`PySys_SetArgv` and carefully consider whether the |
| application should be using :cfunc:`PySys_SetArgvEx` with |
| *updatepath* set to false. |
| |
| .. ====================================================================== |
| |
| |
| .. _acks27: |
| |
| Acknowledgements |
| ================ |
| |
| The author would like to thank the following people for offering |
| suggestions, corrections and assistance with various drafts of this |
| article: Nick Coghlan, Philip Jenvey, Ryan Lovett, R. David Murray, |
| Hugh Secker-Walker. |
| |