1 ****************************
2 What's New in Python 2.7
3 ****************************
5 :Author: A.M. Kuchling (amk at amk.ca)
9 .. Fix accents on Kristjan Valur Jonsson, Fuerstenau, Tarek Ziade.
12 Rules for maintenance:
14 * Anyone can add text to this document. Do not spend very much time
15 on the wording of your changes, because your text will probably
16 get rewritten to some degree.
18 * The maintainer will go through Misc/NEWS periodically and add
19 changes; it's therefore more important to add your changes to
20 Misc/NEWS than to this file.
22 * This is not a complete list of every single change; completeness
23 is the purpose of Misc/NEWS. Some changes I consider too small
24 or esoteric to include. If such a change is added to the text,
25 I'll just remove it. (This is another reason you shouldn't spend
26 too much time on writing your addition.)
28 * If you want to draw your new text to the attention of the
29 maintainer, add 'XXX' to the beginning of the paragraph or
32 * It's OK to just add a fragmentary note about a change. For
33 example: "XXX Describe the transmogrify() function added to the
34 socket module." The maintainer will research the change and
35 write the necessary text.
37 * You can comment out your additions if you like, but it's not
38 necessary (especially when a final release is some months away).
40 * Credit the author of a patch or bugfix. Just the name is
41 sufficient; the e-mail address isn't necessary.
43 * It's helpful to add the bug/patch number in a parenthetical comment.
45 XXX Describe the transmogrify() function added to the socket
47 (Contributed by P.Y. Developer; :issue:`12345`.)
49 This saves the maintainer some effort going through the SVN logs
50 when researching a change.
52 This article explains the new features in Python 2.7. The final
53 release of 2.7 is currently scheduled for June 2010; the detailed
54 schedule is described in :pep:`373`.
56 .. Compare with previous release in 2 - 3 sentences here.
57 add hyperlink when the documentation becomes available online.
59 .. _whatsnew27-python31:
62 =======================
64 Much as Python 2.6 incorporated features from Python 3.0,
65 version 2.7 incorporates some of the new features
66 in Python 3.1. The 2.x series continues to provide tools
67 for migrating to the 3.x series.
69 A partial list of 3.1 features that were backported to 2.7:
71 * A version of the :mod:`io` library, rewritten in C for performance.
72 * The ordered-dictionary type described in :ref:`pep-0372`.
73 * The new format specifier described in :ref:`pep-0378`.
74 * The :class:`memoryview` object.
75 * A small subset of the :mod:`importlib` module `described below <#importlib-section>`__.
76 * Float-to-string and string-to-float conversions now round their
77 results more correctly. And :func:`repr` of a floating-point
78 number *x* returns a result that's guaranteed to round back to the
79 same number when converted back to a string.
80 * The :cfunc:`PyLong_AsLongAndOverflow` C API function.
82 One porting change: the :option:`-3` switch now automatically
83 enables the :option:`-Qwarn` switch that causes warnings
84 about using classic division with integers and long integers.
86 Other new Python3-mode warnings include:
88 * :func:`operator.isCallable` and :func:`operator.sequenceIncludes`,
89 which are not supported in 3.x.
91 .. ========================================================================
92 .. Large, PEP-level features and changes should be described here.
93 .. ========================================================================
97 PEP 372: Adding an ordered dictionary to collections
98 ====================================================
100 Regular Python dictionaries iterate over key/value pairs in arbitrary order.
101 Over the years, a number of authors have written alternative implementations
102 that remember the order that the keys were originally inserted. Based on
103 the experiences from those implementations, a new
104 :class:`collections.OrderedDict` class has been introduced.
106 The :class:`OrderedDict` API is substantially the same as regular dictionaries
107 but will iterate over keys and values in a guaranteed order depending on
108 when a key was first inserted::
110 >>> from collections import OrderedDict
111 >>> d = OrderedDict([('first', 1), ('second', 2),
114 [('first', 1), ('second', 2), ('third', 3)]
116 If a new entry overwrites an existing entry, the original insertion
117 position is left unchanged::
121 [('first', 1), ('second', 4), ('third', 3)]
123 Deleting an entry and reinserting it will move it to the end::
128 [('first', 1), ('third', 3), ('second', 5)]
130 The :meth:`popitem` method has an optional *last* argument
131 that defaults to True. If *last* is True, the most recently
132 added key is returned and removed; if it's False, the
133 oldest key is selected::
135 >>> od = OrderedDict([(x,0) for x in range(20)])
140 >>> od.popitem(False)
142 >>> od.popitem(False)
145 Comparing two ordered dictionaries checks both the keys and values,
146 and requires that the insertion order was the same::
148 >>> od1 = OrderedDict([('first', 1), ('second', 2),
150 >>> od2 = OrderedDict([('third', 3), ('first', 1),
154 >>> # Move 'third' key to the end
155 >>> del od2['third'] ; od2['third'] = 3
159 Comparing an :class:`OrderedDict` with a regular dictionary
160 ignores the insertion order and just compares the keys and values.
162 How does the :class:`OrderedDict` work? It maintains a doubly-linked
163 list of keys, appending new keys to the list as they're inserted. A
164 secondary dictionary maps keys to their corresponding list node, so
165 deletion doesn't have to traverse the entire linked list and therefore
168 .. XXX check O(1)-ness with Raymond
170 The standard library now supports use of ordered dictionaries in several
171 modules. The :mod:`configparser` module uses them by default. This lets
172 configuration files be read, modified, and then written back in their original
173 order. The *_asdict()* method for :func:`collections.namedtuple` now
174 returns an ordered dictionary with the values appearing in the same order as
175 the underlying tuple indicies. The :mod:`json` module is being built-out with
176 an *object_pairs_hook* to allow OrderedDicts to be built by the decoder.
177 Support was also added for third-party tools like `PyYAML <http://pyyaml.org/>`_.
181 :pep:`372` - Adding an ordered dictionary to collections
182 PEP written by Armin Ronacher and Raymond Hettinger;
183 implemented by Raymond Hettinger.
187 PEP 378: Format Specifier for Thousands Separator
188 ====================================================
190 To make program output more readable, it can be useful to add
191 separators to large numbers and render them as
192 18,446,744,073,709,551,616 instead of 18446744073709551616.
194 The fully general solution for doing this is the :mod:`locale` module,
195 which can use different separators ("," in North America, "." in
196 Europe) and different grouping sizes, but :mod:`locale` is complicated
197 to use and unsuitable for multi-threaded applications where different
198 threads are producing output for different locales.
200 Therefore, a simple comma-grouping mechanism has been added to the
201 mini-language used by the string :meth:`format` method. When
202 formatting a floating-point number, simply include a comma between the
203 width and the precision::
205 >>> '{:20,.2}'.format(f)
206 '18,446,744,073,709,551,616.00'
208 This mechanism is not adaptable at all; commas are always used as the
209 separator and the grouping is always into three-digit groups. The
210 comma-formatting mechanism isn't as general as the :mod:`locale`
211 module, but it's easier to use.
213 .. XXX "Format String Syntax" in string.rst could use many more examples.
217 :pep:`378` - Format Specifier for Thousands Separator
218 PEP written by Raymond Hettinger; implemented by Eric Smith.
220 Other Language Changes
221 ======================
223 Some smaller changes made to the core Python language are:
225 * The :keyword:`with` statement can now use multiple context managers
226 in one statement. Context managers are processed from left to right
227 and each one is treated as beginning a new :keyword:`with` statement.
230 with A() as a, B() as b:
231 ... suite of statements ...
237 ... suite of statements ...
239 The :func:`contextlib.nested` function provides a very similar
240 function, so it's no longer necessary and has been deprecated.
242 (Proposed in http://codereview.appspot.com/53094; implemented by
245 * Conversions between floating-point numbers and strings are
246 now correctly rounded on most platforms. These conversions occur
247 in many different places: :func:`str` on
248 floats and complex numbers; the :class:`float` and :class:`complex`
250 numeric formatting; serialization and
251 deserialization of floats and complex numbers using the
252 :mod:`marshal`, :mod:`pickle`
253 and :mod:`json` modules;
254 parsing of float and imaginary literals in Python code;
255 and :class:`Decimal`-to-float conversion.
257 Related to this, the :func:`repr` of a floating-point number *x*
258 now returns a result based on the shortest decimal string that's
259 guaranteed to round back to *x* under correct rounding (with
260 round-half-to-even rounding mode). Previously it gave a string
261 based on rounding x to 17 decimal digits.
263 The rounding library responsible for this improvement works on
264 Windows, and on Unix platforms using the gcc, icc, or suncc
265 compilers. There may be a small number of platforms where correct
266 operation of this code cannot be guaranteed, so the code is not
267 used on such systems. You can find out which code is being used
268 by checking :data:`sys.float_repr_style`, which will be ``short``
269 if the new code is in use and ``legacy`` if it isn't.
271 Implemented by Eric Smith and Mark Dickinson, using David Gay's
272 :file:`dtoa.c` library; :issue:`7117`.
274 * The :meth:`str.format` method now supports automatic numbering of the replacement
275 fields. This makes using :meth:`str.format` more closely resemble using
278 >>> '{}:{}:{}'.format(2009, 04, 'Sunday')
280 >>> '{}:{}:{day}'.format(2009, 4, day='Sunday')
283 The auto-numbering takes the fields from left to right, so the first ``{...}``
284 specifier will use the first argument to :meth:`str.format`, the next
285 specifier will use the next argument, and so on. You can't mix auto-numbering
286 and explicit numbering -- either number all of your specifier fields or none
287 of them -- but you can mix auto-numbering and named fields, as in the second
288 example above. (Contributed by Eric Smith; :issue:`5237`.)
290 Complex numbers now correctly support usage with :func:`format`.
291 Specifying a precision or comma-separation applies to both the real
292 and imaginary parts of the number, but a specified field width and
293 alignment is applied to the whole of the resulting ``1.5+3j``
294 output. (Contributed by Eric Smith; :issue:`1588`.)
296 The 'F' format code now always formats its output using uppercase characters,
297 so it will now produce 'INF' and 'NAN'.
298 (Contributed by Eric Smith; :issue:`3382`.)
300 * The :func:`int` and :func:`long` types gained a ``bit_length``
301 method that returns the number of bits necessary to represent
302 its argument in binary::
312 >>> (n+1).bit_length()
315 (Contributed by Fredrik Johansson and Victor Stinner; :issue:`3439`.)
317 * Conversions from long integers and regular integers to floating
318 point now round differently, returning the floating-point number
319 closest to the number. This doesn't matter for small integers that
320 can be converted exactly, but for large numbers that will
321 unavoidably lose precision, Python 2.7 now approximates more
322 closely. For example, Python 2.6 computed the following::
324 >>> n = 295147905179352891391
326 2.9514790517935283e+20
327 >>> n - long(float(n))
330 Python 2.7's floating-point result is larger, but much closer to the
333 >>> n = 295147905179352891391
335 2.9514790517935289e+20
340 (Implemented by Mark Dickinson; :issue:`3166`.)
342 Integer division is also more accurate in its rounding behaviours. (Also
343 implemented by Mark Dickinson; :issue:`1811`.)
345 * The :class:`bytearray` type's :meth:`translate` method now accepts
346 ``None`` as its first argument. (Fixed by Georg Brandl;
349 * When using ``@classmethod`` and ``@staticmethod`` to wrap
350 methods as class or static methods, the wrapper object now
351 exposes the wrapped function as their :attr:`__func__` attribute.
352 (Contributed by Amaury Forgeot d'Arc, after a suggestion by
353 George Sakkis; :issue:`5982`.)
355 * A new encoding named "cp720", used primarily for Arabic text, is now
356 supported. (Contributed by Alexander Belchenko and Amaury Forgeot
357 d'Arc; :issue:`1616979`.)
359 * The :class:`file` object will now set the :attr:`filename` attribute
360 on the :exc:`IOError` exception when trying to open a directory
361 on POSIX platforms. (Noted by Jan Kaliszewski; :issue:`4764`.)
363 * The Python tokenizer now translates line endings itself, so the
364 :func:`compile` built-in function can now accept code using any
365 line-ending convention. Additionally, it no longer requires that the
366 code end in a newline.
368 * Extra parentheses in function definitions are illegal in Python 3.x,
369 meaning that you get a syntax error from ``def f((x)): pass``. In
370 Python3-warning mode, Python 2.7 will now warn about this odd usage.
371 (Noted by James Lingard; :issue:`7362`.)
373 .. ======================================================================
379 Several performance enhancements have been added:
381 .. * A new :program:`configure` option, :option:`--with-computed-gotos`,
382 compiles the main bytecode interpreter loop using a new dispatch
383 mechanism that gives speedups of up to 20%, depending on the system
384 and benchmark. The new mechanism is only supported on certain
385 compilers, such as gcc, SunPro, and icc.
387 * A new opcode was added to perform the initial setup for
388 :keyword:`with` statements, looking up the :meth:`__enter__` and
389 :meth:`__exit__` methods. (Contributed by Benjamin Peterson.)
391 * The garbage collector now performs better for one common usage
392 pattern: when many objects are being allocated without deallocating
393 any of them. This would previously take quadratic
394 time for garbage collection, but now the number of full garbage collections
395 is reduced as the number of objects on the heap grows.
396 The new logic is to only perform a full garbage collection pass when
397 the middle generation has been collected 10 times and when the
398 number of survivor objects from the middle generation exceeds 10% of
399 the number of objects in the oldest generation. (Suggested by Martin
400 von Loewis and implemented by Antoine Pitrou; :issue:`4074`.)
402 * The garbage collector tries to avoid tracking simple containers
403 which can't be part of a cycle. In Python 2.7, this is now true for
404 tuples and dicts containing atomic types (such as ints, strings,
405 etc.). Transitively, a dict containing tuples of atomic types won't
406 be tracked either. This helps reduce the cost of each
407 garbage collection by decreasing the number of objects to be
408 considered and traversed by the collector.
409 (Contributed by Antoine Pitrou; :issue:`4688`.)
411 * Long integers are now stored internally either in base 2**15 or in base
412 2**30, the base being determined at build time. Previously, they
413 were always stored in base 2**15. Using base 2**30 gives
414 significant performance improvements on 64-bit machines, but
415 benchmark results on 32-bit machines have been mixed. Therefore,
416 the default is to use base 2**30 on 64-bit machines and base 2**15
417 on 32-bit machines; on Unix, there's a new configure option
418 :option:`--enable-big-digits` that can be used to override this default.
420 Apart from the performance improvements this change should be
421 invisible to end users, with one exception: for testing and
422 debugging purposes there's a new structseq ``sys.long_info`` that
423 provides information about the internal format, giving the number of
424 bits per digit and the size in bytes of the C type used to store
429 sys.long_info(bits_per_digit=30, sizeof_digit=4)
431 (Contributed by Mark Dickinson; :issue:`4258`.)
433 Another set of changes made long objects a few bytes smaller: 2 bytes
434 smaller on 32-bit systems and 6 bytes on 64-bit.
435 (Contributed by Mark Dickinson; :issue:`5260`.)
437 * The division algorithm for long integers has been made faster
438 by tightening the inner loop, doing shifts instead of multiplications,
439 and fixing an unnecessary extra iteration.
440 Various benchmarks show speedups of between 50% and 150% for long
441 integer divisions and modulo operations.
442 (Contributed by Mark Dickinson; :issue:`5512`.)
443 Bitwise operations are also significantly faster (initial patch by
444 Gregory Smith; :issue:`1087418`).
446 * The implementation of ``%`` checks for the left-side operand being
447 a Python string and special-cases it; this results in a 1-3%
448 performance increase for applications that frequently use ``%``
449 with strings, such as templating libraries.
450 (Implemented by Collin Winter; :issue:`5176`.)
452 * List comprehensions with an ``if`` condition are compiled into
453 faster bytecode. (Patch by Antoine Pitrou, back-ported to 2.7
454 by Jeffrey Yasskin; :issue:`4715`.)
456 * Converting an integer or long integer to a decimal string was made
457 faster by special-casing base 10 instead of using a generalized
458 conversion function that supports arbitrary bases.
459 (Patch by Gawain Bolton; :issue:`6713`.)
461 * The :meth:`rindex`, :meth:`rpartition`, and :meth:`rsplit` methods
462 of string objects now uses a fast reverse-search algorithm instead of
463 a character-by-character scan. This is often faster by a factor of 10.
464 (Added by Florent Xicluna; :issue:`7462`.)
466 * The :mod:`pickle` and :mod:`cPickle` modules now automatically
467 intern the strings used for attribute names, reducing memory usage
468 of the objects resulting from unpickling. (Contributed by Jake
469 McGuire; :issue:`5084`.)
471 * The :mod:`cPickle` module now special-cases dictionaries,
472 nearly halving the time required to pickle them.
473 (Contributed by Collin Winter; :issue:`5670`.)
475 .. ======================================================================
477 New and Improved Modules
478 ========================
480 As in every release, Python's standard library received a number of
481 enhancements and bug fixes. Here's a partial list of the most notable
482 changes, sorted alphabetically by module name. Consult the
483 :file:`Misc/NEWS` file in the source tree for a more complete list of
484 changes, or look through the Subversion logs for all the details.
486 * The :mod:`bdb` module's base debugging class :class:`Bdb`
487 gained a feature for skipping modules. The constructor
488 now takes an iterable containing glob-style patterns such as
489 ``django.*``; the debugger will not step into stack frames
490 from a module that matches one of these patterns.
491 (Contributed by Maru Newby after a suggestion by
492 Senthil Kumaran; :issue:`5142`.)
494 * The :mod:`bz2` module's :class:`BZ2File` now supports the context
495 management protocol, so you can write ``with bz2.BZ2File(...) as f: ...``.
496 (Contributed by Hagen Fuerstenau; :issue:`3860`.)
498 * New class: the :class:`Counter` class in the :mod:`collections` module is
499 useful for tallying data. :class:`Counter` instances behave mostly
500 like dictionaries but return zero for missing keys instead of
501 raising a :exc:`KeyError`:
504 :options: +NORMALIZE_WHITESPACE
506 >>> from collections import Counter
508 >>> for letter in 'here is a sample of english text':
512 Counter({' ': 6, 'e': 5, 's': 3, 'a': 2, 'i': 2, 'h': 2,
513 'l': 2, 't': 2, 'g': 1, 'f': 1, 'm': 1, 'o': 1, 'n': 1,
514 'p': 1, 'r': 1, 'x': 1})
520 There are two additional :class:`Counter` methods: :meth:`most_common`
521 returns the N most common elements and their counts, and :meth:`elements`
522 returns an iterator over the contained element, repeating each element
523 as many times as its count::
526 [(' ', 6), ('e', 5), ('s', 3), ('a', 2), ('i', 2)]
528 'a', 'a', ' ', ' ', ' ', ' ', ' ', ' ',
529 'e', 'e', 'e', 'e', 'e', 'g', 'f', 'i', 'i',
530 'h', 'h', 'm', 'l', 'l', 'o', 'n', 'p', 's',
531 's', 's', 'r', 't', 't', 'x'
533 Contributed by Raymond Hettinger; :issue:`1696199`.
535 The new `OrderedDict` class is described in the earlier section
538 The :class:`namedtuple` class now has an optional *rename* parameter.
539 If *rename* is true, field names that are invalid because they've
540 been repeated or that aren't legal Python identifiers will be
541 renamed to legal names that are derived from the field's
542 position within the list of fields:
544 >>> from collections import namedtuple
545 >>> T = namedtuple('T', ['field1', '$illegal', 'for', 'field2'], rename=True)
547 ('field1', '_1', '_2', 'field2')
549 (Added by Raymond Hettinger; :issue:`1818`.)
551 The :class:`deque` data type now exposes its maximum length as the
552 read-only :attr:`maxlen` attribute, and has a
553 :meth:`reverse` method that reverses the elements of the deque in-place.
554 (Added by Raymond Hettinger.)
556 * The :mod:`copy` module's :func:`deepcopy` function will now
557 correctly copy bound instance methods. (Implemented by
558 Robert Collins; :issue:`1515`.)
560 * The :mod:`ctypes` module now always converts ``None`` to a C NULL
561 pointer for arguments declared as pointers. (Changed by Thomas
562 Heller; :issue:`4606`.)
564 * New method: the :mod:`datetime` module's :class:`timedelta` class
565 gained a :meth:`total_seconds` method that returns the number of seconds
566 in the duration. (Contributed by Brian Quinlan; :issue:`5788`.)
568 * New method: the :class:`Decimal` class gained a
569 :meth:`from_float` class method that performs an exact conversion
570 of a floating-point number to a :class:`Decimal`.
571 Note that this is an **exact** conversion that strives for the
572 closest decimal approximation to the floating-point representation's value;
573 the resulting decimal value will therefore still include the inaccuracy,
575 For example, ``Decimal.from_float(0.1)`` returns
576 ``Decimal('0.1000000000000000055511151231257827021181583404541015625')``.
577 (Implemented by Raymond Hettinger; :issue:`4796`.)
579 The constructor for :class:`Decimal` now accepts non-European
580 Unicode characters, such as Arabic-Indic digits. (Contributed by
581 Mark Dickinson; :issue:`6595`.)
583 When using :class:`Decimal` instances with a string's
584 :meth:`format` method, the default alignment was previously
585 left-alignment. This has been changed to right-alignment, which seems
586 more sensible for numeric types. (Changed by Mark Dickinson; :issue:`6857`.)
588 * Distutils is being more actively developed, thanks to Tarek Ziade
589 who has taken over maintenance of the package. A new
590 :file:`setup.py` subcommand, ``check``, will
591 check that the arguments being passed to the :func:`setup` function
592 are complete and correct (:issue:`5732`).
594 :func:`distutils.sdist.add_defaults` now uses
595 *package_dir* and *data_files* to create the MANIFEST file.
596 :mod:`distutils.sysconfig` now reads the :envvar:`AR` and
597 :envvar:`ARFLAGS` environment variables.
599 .. ARFLAGS done in #5941
601 It is no longer mandatory to store clear-text passwords in the
602 :file:`.pypirc` file when registering and uploading packages to PyPI. As long
603 as the username is present in that file, the :mod:`distutils` package will
604 prompt for the password if not present. (Added by Tarek Ziade,
605 based on an initial contribution by Nathan Van Gheem; :issue:`4394`.)
607 A Distutils setup can now specify that a C extension is optional by
608 setting the *optional* option setting to true. If this optional is
609 supplied, failure to build the extension will not abort the build
610 process, but instead simply not install the failing extension.
611 (Contributed by Georg Brandl; :issue:`5583`.)
613 The :class:`distutils.dist.DistributionMetadata` class'
614 :meth:`read_pkg_file` method will read the contents of a package's
615 :file:`PKG-INFO` metadata file. For an example of its use,
616 XXX link to file:///MacDev/svn.python.org/python-trunk/Doc/build/html/distutils/examples.html#reading-the-metadata
617 (Contributed by Tarek Ziade; :issue:`7457`.)
619 :file:`setup.py` files will now accept a :option:`--no-user-cfg` switch
620 to skip reading the :file:`~/.pydistutils.cfg` file. (Suggested by
621 by Michael Hoffman, and implemented by Paul Winkler; :issue:`1180`.)
623 * The :class:`Fraction` class now accepts two rational numbers
624 as arguments to its constructor.
625 (Implemented by Mark Dickinson; :issue:`5812`.)
627 * The :mod:`ftplib` module gained the ability to establish secure FTP
628 connections using TLS encapsulation of authentication as well as
629 subsequent control and data transfers. This is provided by the new
630 :class:`ftplib.FTP_TLS` class.
631 (Contributed by Giampaolo Rodola', :issue:`2054`.) The :meth:`storbinary`
632 method for binary uploads can now restart uploads thanks to an added
633 *rest* parameter (patch by Pablo Mouzo; :issue:`6845`.)
635 * New function: the :mod:`gc` module's :func:`is_tracked` returns
636 true if a given instance is tracked by the garbage collector, false
637 otherwise. (Contributed by Antoine Pitrou; :issue:`4688`.)
639 * The :mod:`gzip` module's :class:`GzipFile` now supports the context
640 management protocol, so you can write ``with gzip.GzipFile(...) as f: ...``.
641 (Contributed by Hagen Fuerstenau; :issue:`3860`.)
642 It's now possible to override the modification time
643 recorded in a gzipped file by providing an optional timestamp to
644 the constructor. (Contributed by Jacques Frechet; :issue:`4272`.)
646 * The default :class:`HTTPResponse` class used by the :mod:`httplib` module now
647 supports buffering, resulting in much faster reading of HTTP responses.
648 (Contributed by Kristjan Valur Jonsson; :issue:`4879`.)
650 * The :mod:`imaplib` module now supports IPv6 addresses.
651 (Contributed by Derek Morr; :issue:`1655`.)
653 * The :mod:`io` library has been upgraded to the version shipped with
654 Python 3.1. For 3.1, the I/O library was entirely rewritten in C
655 and is 2 to 20 times faster depending on the task at hand. The
656 original Python version was renamed to the :mod:`_pyio` module.
658 One minor resulting change: the :class:`io.TextIOBase` class now
659 has an :attr:`errors` attribute giving the error setting
660 used for encoding and decoding errors (one of ``'strict'``, ``'replace'``,
663 The :class:`io.FileIO` class now raises an :exc:`OSError` when passed
664 an invalid file descriptor. (Implemented by Benjamin Peterson;
667 * New function: ``itertools.compress(data, selectors)`` takes two
668 iterators. Elements of *data* are returned if the corresponding
669 value in *selectors* is true::
671 itertools.compress('ABCDEF', [1,0,1,0,1,1]) =>
674 New function: ``itertools.combinations_with_replacement(iter, r)``
675 returns all the possible *r*-length combinations of elements from the
676 iterable *iter*. Unlike :func:`combinations`, individual elements
677 can be repeated in the generated combinations::
679 itertools.combinations_with_replacement('abc', 2) =>
680 ('a', 'a'), ('a', 'b'), ('a', 'c'),
681 ('b', 'b'), ('b', 'c'), ('c', 'c')
683 Note that elements are treated as unique depending on their position
684 in the input, not their actual values.
686 The :class:`itertools.count` function now has a *step* argument that
687 allows incrementing by values other than 1. :func:`count` also
688 now allows keyword arguments, and using non-integer values such as
689 floats or :class:`Decimal` instances. (Implemented by Raymond
690 Hettinger; :issue:`5032`.)
692 :func:`itertools.combinations` and :func:`itertools.product` were
693 previously raising :exc:`ValueError` for values of *r* larger than
694 the input iterable. This was deemed a specification error, so they
695 now return an empty iterator. (Fixed by Raymond Hettinger; :issue:`4816`.)
697 * The :mod:`json` module was upgraded to version 2.0.9 of the
698 simplejson package, which includes a C extension that makes
699 encoding and decoding faster.
700 (Contributed by Bob Ippolito; :issue:`4136`.)
702 To support the new :class:`OrderedDict` type, :func:`json.load`
703 now has an optional *object_pairs_hook* parameter that will be called
704 with any object literal that decodes to a list of pairs.
705 (Contributed by Raymond Hettinger; :issue:`5381`.)
707 * New functions: the :mod:`math` module gained
708 :func:`erf` and :func:`erfc` for the error function and the complementary error function,
709 :func:`expm1` which computes ``e**x - 1`` with more precision than
710 using :func:`exp` and subtracting 1,
711 :func:`gamma` for the Gamma function, and
712 :func:`lgamma` for the natural log of the Gamma function.
713 (Contributed by Mark Dickinson and nirinA raseliarison; :issue:`3366`.)
715 * The :mod:`multiprocessing` module's :class:`Manager*` classes
716 can now be passed a callable that will be called whenever
717 a subprocess is started, along with a set of arguments that will be
718 passed to the callable.
719 (Contributed by lekma; :issue:`5585`.)
721 * The :mod:`nntplib` module now supports IPv6 addresses.
722 (Contributed by Derek Morr; :issue:`1664`.)
724 * New functions: the :mod:`os` module wraps the following POSIX system
725 calls: :func:`getresgid` and :func:`getresuid`, which return the
726 real, effective, and saved GIDs and UIDs;
727 :func:`setresgid` and :func:`setresuid`, which set
728 real, effective, and saved GIDs and UIDs to new values;
729 :func:`initgroups`. (GID/UID functions
730 contributed by Travis H.; :issue:`6508`. Support for initgroups added
731 by Jean-Paul Calderone; :issue:`7333`.)
733 * The :mod:`pydoc` module now has help for the various symbols that Python
734 uses. You can now do ``help('<<')`` or ``help('@')``, for example.
735 (Contributed by David Laban; :issue:`4739`.)
737 * The :mod:`re` module's :func:`split`, :func:`sub`, and :func:`subn`
738 now accept an optional *flags* argument, for consistency with the
739 other functions in the module. (Added by Gregory P. Smith.)
741 * The :mod:`shutil` module's :func:`copyfile` and :func:`copytree`
742 functions now raises a :exc:`SpecialFileError` exception when
743 asked to copy a named pipe. Previously the code would treat
744 named pipes like a regular file by opening them for reading, and
745 this would block indefinitely. (Fixed by Antoine Pitrou; :issue:`3002`.)
747 * New functions: in the :mod:`site` module, three new functions
748 return various site- and user-specific paths.
749 :func:`getsitepackages` returns a list containing all
750 global site-packages directories, and
751 :func:`getusersitepackages` returns the path of the user's
752 site-packages directory.
753 :func:`getuserbase` returns the value of the :envvar:`USER_BASE`
754 environment variable, giving the path to a directory that can be used
756 (Contributed by Tarek Ziade; :issue:`6693`.)
758 * The :mod:`socket` module's :class:`SSL` objects now support the
759 buffer API, which fixed a test suite failure. (Fixed by Antoine Pitrou;
762 * The :mod:`SocketServer` module's :class:`TCPServer` class now
763 has a :attr:`disable_nagle_algorithm` class attribute.
764 The default value is False; if overridden to be True,
765 new request connections will have the TCP_NODELAY option set to
766 prevent buffering many small sends into a single TCP packet.
767 (Contributed by Kristjan Valur Jonsson; :issue:`6192`.)
769 * The :mod:`struct` module will no longer silently ignore overflow
770 errors when a value is too large for a particular integer format
771 code (one of ``bBhHiIlLqQ``); it now always raises a
772 :exc:`struct.error` exception. (Changed by Mark Dickinson;
775 * New function: the :mod:`subprocess` module's
776 :func:`check_output` runs a command with a specified set of arguments
777 and returns the command's output as a string when the command runs without
778 error, or raises a :exc:`CalledProcessError` exception otherwise.
782 >>> subprocess.check_output(['df', '-h', '.'])
783 'Filesystem Size Used Avail Capacity Mounted on\n
784 /dev/disk0s2 52G 49G 3.0G 94% /\n'
786 >>> subprocess.check_output(['df', '-h', '/bogus'])
788 subprocess.CalledProcessError: Command '['df', '-h', '/bogus']' returned non-zero exit status 1
790 (Contributed by Gregory P. Smith.)
792 * New function: :func:`is_declared_global` in the :mod:`symtable` module
793 returns true for variables that are explicitly declared to be global,
794 false for ones that are implicitly global.
795 (Contributed by Jeremy Hylton.)
797 * The ``sys.version_info`` value is now a named tuple, with attributes
798 named ``major``, ``minor``, ``micro``, ``releaselevel``, and ``serial``.
799 (Contributed by Ross Light; :issue:`4285`.)
801 * The :mod:`tarfile` module now supports filtering the :class:`TarInfo`
802 objects being added to a tar file. When you call :meth:`TarFile.add`,
803 instance, you may supply an optional *filter* argument
804 that's a callable. The *filter* callable will be passed the
805 :class:`TarInfo` for every file being added, and can modify and return it.
806 If the callable returns ``None``, the file will be excluded from the
807 resulting archive. This is more powerful than the existing
808 *exclude* argument, which has therefore been deprecated.
809 (Added by Lars Gustaebel; :issue:`6856`.)
811 * The :mod:`threading` module's :meth:`Event.wait` method now returns
812 the internal flag on exit. This means the method will usually
813 return true because :meth:`wait` is supposed to block until the
814 internal flag becomes true. The return value will only be false if
815 a timeout was provided and the operation timed out.
816 (Contributed by Tim Lesher; :issue:`1674032`.)
818 * The :func:`is_zipfile` function in the :mod:`zipfile` module now
819 accepts a file object, in addition to the path names accepted in earlier
820 versions. (Contributed by Gabriel Genellina; :issue:`4756`.)
822 :mod:`zipfile` now supports archiving empty directories and
823 extracts them correctly. (Fixed by Kuba Wieczorek; :issue:`4710`.)
825 .. ======================================================================
826 .. whole new modules get described in subsections here
828 Unit Testing Enhancements
829 ---------------------------------
831 The :mod:`unittest` module was enhanced in several ways.
832 The progress messages now shows 'x' for expected failures
833 and 'u' for unexpected successes when run in verbose mode.
834 (Contributed by Benjamin Peterson.)
835 Test cases can raise the :exc:`SkipTest` exception to skip a test.
838 .. XXX describe test discovery (Contributed by Michael Foord; :issue:`6001`.)
840 The error messages for :meth:`assertEqual`,
841 :meth:`assertTrue`, and :meth:`assertFalse`
842 failures now provide more information. If you set the
843 :attr:`longMessage` attribute of your :class:`TestCase` classes to
844 true, both the standard error message and any additional message you
845 provide will be printed for failures. (Added by Michael Foord; :issue:`5663`.)
847 The :meth:`assertRaises` and :meth:`failUnlessRaises` methods now
848 return a context handler when called without providing a callable
849 object to run. For example, you can write this::
851 with self.assertRaises(KeyError):
854 (Implemented by Antoine Pitrou; :issue:`4444`.)
856 The methods :meth:`addCleanup` and :meth:`doCleanups` were added.
857 :meth:`addCleanup` allows you to add cleanup functions that
858 will be called unconditionally (after :meth:`setUp` if
859 :meth:`setUp` fails, otherwise after :meth:`tearDown`). This allows
860 for much simpler resource allocation and deallocation during tests.
863 A number of new methods were added that provide more specialized
864 tests. Many of these methods were written by Google engineers
865 for use in their test suites; Gregory P. Smith, Michael Foord, and
866 GvR worked on merging them into Python's version of :mod:`unittest`.
868 * :meth:`assertIsNone` and :meth:`assertIsNotNone` take one
869 expression and verify that the result is or is not ``None``.
871 * :meth:`assertIs` and :meth:`assertIsNot` take two values and check
872 whether the two values evaluate to the same object or not.
873 (Added by Michael Foord; :issue:`2578`.)
875 * :meth:`assertIsInstance` and :meth:`assertNotIsInstance` check whether
876 the resulting object is an instance of a particular class, or of
877 one of a tuple of classes. (Added by Georg Brandl; :issue:`7031`.)
879 * :meth:`assertGreater`, :meth:`assertGreaterEqual`,
880 :meth:`assertLess`, and :meth:`assertLessEqual` compare
883 * :meth:`assertMultiLineEqual` compares two strings, and if they're
884 not equal, displays a helpful comparison that highlights the
885 differences in the two strings.
887 * :meth:`assertRegexpMatches` checks whether its first argument is a
888 string matching a regular expression provided as its second argument.
890 * :meth:`assertRaisesRegexp` checks whether a particular exception
891 is raised, and then also checks that the string representation of
892 the exception matches the provided regular expression.
894 * :meth:`assertIn` and :meth:`assertNotIn` tests whether
895 *first* is or is not in *second*.
897 * :meth:`assertSameElements` tests whether two provided sequences
898 contain the same elements.
900 * :meth:`assertSetEqual` compares whether two sets are equal, and
901 only reports the differences between the sets in case of error.
903 * Similarly, :meth:`assertListEqual` and :meth:`assertTupleEqual`
904 compare the specified types and explain the differences.
905 More generally, :meth:`assertSequenceEqual` compares two sequences
906 and can optionally check whether both sequences are of a
909 * :meth:`assertDictEqual` compares two dictionaries and reports the
910 differences. :meth:`assertDictContainsSubset` checks whether
911 all of the key/value pairs in *first* are found in *second*.
913 * :meth:`assertAlmostEqual` and :meth:`assertNotAlmostEqual` short-circuit
914 (automatically pass or fail without checking decimal places) if the objects
917 * :meth:`loadTestsFromName` properly honors the ``suiteClass`` attribute of
918 the :class:`TestLoader`. (Fixed by Mark Roddy; :issue:`6866`.)
920 * A new hook, :meth:`addTypeEqualityFunc` takes a type object and a
921 function. The :meth:`assertEqual` method will use the function
922 when both of the objects being compared are of the specified type.
923 This function should compare the two objects and raise an
924 exception if they don't match; it's a good idea for the function
925 to provide additional information about why the two objects are
926 matching, much as the new sequence comparison methods do.
928 :func:`unittest.main` now takes an optional ``exit`` argument.
929 If False ``main`` doesn't call :func:`sys.exit` allowing it to
930 be used from the interactive interpreter. :issue:`3379`.
932 :class:`TestResult` has new :meth:`startTestRun` and
933 :meth:`stopTestRun` methods; called immediately before
934 and after a test run. :issue:`5728` by Robert Collins.
936 With all these changes, the :file:`unittest.py` was becoming awkwardly
937 large, so the module was turned into a package and the code split into
938 several files (by Benjamin Peterson). This doesn't affect how the
942 .. _importlib-section:
944 importlib: Importing Modules
945 ------------------------------
947 Python 3.1 includes the :mod:`importlib` package, a re-implementation
948 of the logic underlying Python's :keyword:`import` statement.
949 :mod:`importlib` is useful for implementors of Python interpreters and
950 to users who wish to write new importers that can participate in the
951 import process. Python 2.7 doesn't contain the complete
952 :mod:`importlib` package, but instead has a tiny subset that contains
953 a single function, :func:`import_module`.
955 ``import_module(name, package=None)`` imports a module. *name* is
956 a string containing the module or package's name. It's possible to do
957 relative imports by providing a string that begins with a ``.``
958 character, such as ``..utils.errors``. For relative imports, the
959 *package* argument must be provided and is the name of the package that
960 will be used as the anchor for
961 the relative import. :func:`import_module` both inserts the imported
962 module into ``sys.modules`` and returns the module object.
964 Here are some examples::
966 >>> from importlib import import_module
967 >>> anydbm = import_module('anydbm') # Standard absolute import
969 <module 'anydbm' from '/p/python/Lib/anydbm.py'>
970 >>> # Relative import
971 >>> sysconfig = import_module('..sysconfig', 'distutils.command')
973 <module 'distutils.sysconfig' from '/p/python/Lib/distutils/sysconfig.pyc'>
975 :mod:`importlib` was implemented by Brett Cannon and introduced in
979 ttk: Themed Widgets for Tk
980 --------------------------
982 Tcl/Tk 8.5 includes a set of themed widgets that re-implement basic Tk
983 widgets but have a more customizable appearance and can therefore more
984 closely resemble the native platform's widgets. This widget
985 set was originally called Tile, but was renamed to Ttk (for "themed Tk")
986 on being added to Tcl/Tck release 8.5.
988 XXX write a brief discussion and an example here.
990 The :mod:`ttk` module was written by Guilherme Polo and added in
991 :issue:`2983`. An alternate version called ``Tile.py``, written by
992 Martin Franklin and maintained by Kevin Walzer, was proposed for
993 inclusion in :issue:`2618`, but the authors argued that Guilherme
994 Polo's work was more comprehensive.
997 Deprecations and Removals
998 =========================
1000 * :func:`contextlib.nested`, which allows handling more than one context manager
1001 with one :keyword:`with` statement, has been deprecated; :keyword:`with`
1002 supports multiple context managers syntactically now.
1004 .. ======================================================================
1007 Build and C API Changes
1008 =======================
1010 Changes to Python's build process and to the C API include:
1012 * If you use the :file:`.gdbinit` file provided with Python,
1013 the "pyo" macro in the 2.7 version now works correctly when the thread being
1014 debugged doesn't hold the GIL; the macro now acquires it before printing.
1015 (Contributed by Victor Stinner; :issue:`3632`.)
1017 * :cfunc:`Py_AddPendingCall` is now thread-safe, letting any
1018 worker thread submit notifications to the main Python thread. This
1019 is particularly useful for asynchronous IO operations.
1020 (Contributed by Kristjan Valur Jonsson; :issue:`4293`.)
1022 * New function: :cfunc:`PyCode_NewEmpty` creates an empty code object;
1023 only the filename, function name, and first line number are required.
1024 This is useful to extension modules that are attempting to
1025 construct a more useful traceback stack. Previously such
1026 extensions needed to call :cfunc:`PyCode_New`, which had many
1027 more arguments. (Added by Jeffrey Yasskin.)
1029 * New function: :cfunc:`PyErr_NewExceptionWithDoc` creates a new
1030 exception class, just as the existing :cfunc:`PyErr_NewException` does,
1031 but takes an extra ``char *`` argument containing the docstring for the
1032 new exception class. (Added by the 'lekma' user on the Python bug tracker;
1035 * New function: :cfunc:`PyFrame_GetLineNumber` takes a frame object
1036 and returns the line number that the frame is currently executing.
1037 Previously code would need to get the index of the bytecode
1038 instruction currently executing, and then look up the line number
1039 corresponding to that address. (Added by Jeffrey Yasskin.)
1041 * New function: :cfunc:`PyLong_AsLongAndOverflow` approximates a Python long
1042 integer as a C :ctype:`long`. If the number is too large to fit into
1043 a :ctype:`long`, an *overflow* flag is set and returned to the caller.
1044 (Contributed by Case Van Horsen; :issue:`7528`.)
1046 * New function: stemming from the rewrite of string-to-float conversion,
1047 a new :cfunc:`PyOS_string_to_double` function was added. The old
1048 :cfunc:`PyOS_ascii_strtod` and :cfunc:`PyOS_ascii_atof` functions
1051 * New macros: the Python header files now define the following macros:
1052 :cmacro:`Py_ISALNUM`,
1053 :cmacro:`Py_ISALPHA`,
1054 :cmacro:`Py_ISDIGIT`,
1055 :cmacro:`Py_ISLOWER`,
1056 :cmacro:`Py_ISSPACE`,
1057 :cmacro:`Py_ISUPPER`,
1058 :cmacro:`Py_ISXDIGIT`,
1059 and :cmacro:`Py_TOLOWER`, :cmacro:`Py_TOUPPER`.
1060 All of these functions are analogous to the C
1061 standard macros for classifying characters, but ignore the current
1062 locale setting, because in
1063 several places Python needs to analyze characters in a
1064 locale-independent way. (Added by Eric Smith;
1067 .. XXX these macros don't seem to be described in the c-api docs.
1069 * New format codes: the :cfunc:`PyFormat_FromString`,
1070 :cfunc:`PyFormat_FromStringV`, and :cfunc:`PyErr_Format` now
1071 accepts ``%lld`` and ``%llu`` format codes for displaying values of
1072 C's :ctype:`long long` types.
1073 (Contributed by Mark Dickinson; :issue:`7228`.)
1075 * The complicated interaction between threads and process forking has
1076 been changed. Previously, the child process created by
1077 :func:`os.fork` might fail because the child is created with only a
1078 single thread running, the thread performing the :func:`os.fork`.
1079 If other threads were holding a lock, such as Python's import lock,
1080 when the fork was performed, the lock would still be marked as
1081 "held" in the new process. But in the child process nothing would
1082 ever release the lock, since the other threads weren't replicated,
1083 and the child process would no longer be able to perform imports.
1085 Python 2.7 now acquires the import lock before performing an
1086 :func:`os.fork`, and will also clean up any locks created using the
1087 :mod:`threading` module. C extension modules that have internal
1088 locks, or that call :cfunc:`fork()` themselves, will not benefit
1091 (Fixed by Thomas Wouters; :issue:`1590864`.)
1093 * The :cfunc:`Py_Finalize` function now calls the internal
1094 :func:`threading._shutdown` function; this prevents some exceptions from
1095 being raised when an interpreter shuts down.
1096 (Patch by Adam Olsen; :issue:`1722344`.)
1098 * Global symbols defined by the :mod:`ctypes` module are now prefixed
1099 with ``Py``, or with ``_ctypes``. (Implemented by Thomas
1100 Heller; :issue:`3102`.)
1102 * New configure option: the :option:`--with-system-expat` switch allows
1103 building the :mod:`pyexpat` module to use the system Expat library.
1104 (Contributed by Arfrever Frehtes Taifersar Arahesis; :issue:`7609`.)
1106 * New configure option: Compiling Python with the
1107 :option:`--with-valgrind` option will now disable the pymalloc
1108 allocator, which is difficult for the Valgrind to analyze correctly.
1109 Valgrind will therefore be better at detecting memory leaks and
1110 overruns. (Contributed by James Henstridge; :issue:`2422`.)
1112 * New configure option: you can now supply no arguments to
1113 :option:`--with-dbmliborder=` in order to build none of the various
1114 DBM modules. (Added by Arfrever Frehtes Taifersar Arahesis;
1117 * The :program:`configure` script now checks for floating-point rounding bugs
1118 on certain 32-bit Intel chips and defines a :cmacro:`X87_DOUBLE_ROUNDING`
1119 preprocessor definition. No code currently uses this definition,
1120 but it's available if anyone wishes to use it.
1121 (Added by Mark Dickinson; :issue:`2937`.)
1123 * The build process now creates the necessary files for pkg-config
1124 support. (Contributed by Clinton Roy; :issue:`3585`.)
1126 * The build process now supports Subversion 1.7. (Contributed by
1127 Arfrever Frehtes Taifersar Arahesis; :issue:`6094`.)
1130 .. ======================================================================
1132 Port-Specific Changes: Windows
1133 -----------------------------------
1135 * The :mod:`msvcrt` module now contains some constants from
1136 the :file:`crtassem.h` header file:
1137 :data:`CRT_ASSEMBLY_VERSION`,
1138 :data:`VC_ASSEMBLY_PUBLICKEYTOKEN`,
1139 and :data:`LIBRARIES_ASSEMBLY_NAME_PREFIX`.
1140 (Contributed by David Cournapeau; :issue:`4365`.)
1142 * The new :cfunc:`_beginthreadex` API is used to start threads, and
1143 the native thread-local storage functions are now used.
1144 (Contributed by Kristjan Valur Jonsson; :issue:`3582`.)
1146 * The :func:`os.listdir` function now correctly fails
1147 for an empty path. (Fixed by Hirokazu Yamamoto; :issue:`5913`.)
1149 * The :mod:`mimelib` module will now read the MIME database from
1150 the Windows registry when initializing.
1151 (Patch by Gabriel Genellina; :issue:`4969`.)
1153 .. ======================================================================
1155 Port-Specific Changes: Mac OS X
1156 -----------------------------------
1158 * The path ``/Library/Python/2.7/site-packages`` is now appended to
1159 ``sys.path``, in order to share added packages between the system
1160 installation and a user-installed copy of the same version.
1161 (Changed by Ronald Oussoren; :issue:`4865`.)
1164 Other Changes and Fixes
1165 =======================
1167 * When importing a module from a :file:`.pyc` or :file:`.pyo` file
1168 with an existing :file:`.py` counterpart, the :attr:`co_filename`
1169 attributes of the resulting code objects are overwritten when the
1170 original filename is obsolete. This can happen if the file has been
1171 renamed, moved, or is accessed through different paths. (Patch by
1172 Ziga Seilnacht and Jean-Paul Calderone; :issue:`1180193`.)
1174 * The :file:`regrtest.py` script now takes a :option:`--randseed=`
1175 switch that takes an integer that will be used as the random seed
1176 for the :option:`-r` option that executes tests in random order.
1177 The :option:`-r` option also reports the seed that was used
1178 (Added by Collin Winter.)
1180 * Another :file:`regrtest.py` switch is :option:`-j`, which
1181 takes an integer specifying how many tests run in parallel. This
1182 allows reducing the total runtime on multi-core machines.
1183 This option is compatible with several other options, including the
1184 :option:`-R` switch which is known to produce long runtimes.
1185 (Added by Antoine Pitrou, :issue:`6152`.) This can also be used
1186 with a new :option:`-F` switch that runs selected tests in a loop
1187 until they fail. (Added by Antoine Pitrou; :issue:`7312`.)
1189 .. ======================================================================
1191 Porting to Python 2.7
1192 =====================
1194 This section lists previously described changes and other bugfixes
1195 that may require changes to your code:
1197 * When using :class:`Decimal` instances with a string's
1198 :meth:`format` method, the default alignment was previously
1199 left-alignment. This has been changed to right-alignment, which might
1200 change the output of your programs.
1201 (Changed by Mark Dickinson; :issue:`6857`.)
1203 Another :meth:`format`-related change: the default precision used
1204 for floating-point and complex numbers was changed from 6 decimal
1205 places to 12, which matches the precision used by :func:`str`.
1206 (Changed by Eric Smith; :issue:`5920`.)
1208 * Because of an optimization for the :keyword:`with` statement, the special
1209 methods :meth:`__enter__` and :meth:`__exit__` must belong to the object's
1210 type, and cannot be directly attached to the object's instance. This
1211 affects new-style classes (derived from :class:`object`) and C extension
1212 types. (:issue:`6101`.)
1214 * The :meth:`readline` method of :class:`StringIO` objects now does
1215 nothing when a negative length is requested, as other file-like
1216 objects do. (:issue:`7348`).
1220 * C extensions that use integer format codes with the ``PyArg_Parse*``
1221 family of functions will now raise a :exc:`TypeError` exception
1222 instead of triggering a :exc:`DeprecationWarning` (:issue:`5080`).
1224 * Use the new :cfunc:`PyOS_string_to_double` function instead of the old
1225 :cfunc:`PyOS_ascii_strtod` and :cfunc:`PyOS_ascii_atof` functions,
1226 which are now deprecated.
1229 .. ======================================================================
1237 The author would like to thank the following people for offering
1238 suggestions, corrections and assistance with various drafts of this
1239 article: Ryan Lovett, Hugh Secker-Walker.