diff options
Diffstat (limited to 'Doc/whatsnew/2.7.rst')
| -rw-r--r-- | Doc/whatsnew/2.7.rst | 94 |
1 files changed, 73 insertions, 21 deletions
diff --git a/Doc/whatsnew/2.7.rst b/Doc/whatsnew/2.7.rst index f7dab79..9182c453 100644 --- a/Doc/whatsnew/2.7.rst +++ b/Doc/whatsnew/2.7.rst @@ -121,6 +121,31 @@ Some smaller changes made to the core Python language are: (Contributed by Fredrik Johansson and Victor Stinner; :issue:`3439`.) +* 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 will now approximate 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`.) + * The :class:`bytearray` type's :meth:`translate` method will now accept ``None`` as its first argument. (Fixed by Georg Brandl; :issue:`4759`.) @@ -220,21 +245,24 @@ changes, or look through the Subversion logs for all the details. * New class: the :class:`Counter` class in the :mod:`collections` module is useful for tallying data. :class:`Counter` instances behave mostly like dictionaries but return zero for missing keys instead of - raising a :exc:`KeyError`:: - - >>> 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 + 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 two additional :class:`Counter` methods: :meth:`most_common` returns the N most common elements and their counts, and :meth:`elements` @@ -247,7 +275,7 @@ changes, or look through the Subversion logs for all the details. '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'] + 's', 's', 'r', 't', 't', 'x' Contributed by Raymond Hettinger; :issue:`1696199`. @@ -257,7 +285,8 @@ changes, or look through the Subversion logs for all the details. renamed to legal names that are derived from the field's position within the list of fields: - >>> T=namedtuple('T', ['field1', '$illegal', 'for', 'field2'], rename=True) + >>> from collections import namedtuple + >>> T = namedtuple('T', ['field1', '$illegal', 'for', 'field2'], rename=True) >>> T._fields ('field1', '_1', '_2', 'field2') @@ -294,6 +323,10 @@ changes, or look through the Subversion logs for all the details. ``Decimal('0.1000000000000000055511151231257827021181583404541015625')``. (Implemented by Raymond Hettinger; :issue:`4796`.) +* The :class:`Fraction` class will now accept two rational numbers + as arguments to its constructor. + (Implemented by Mark Dickinson; :issue:`5812`.) + * New function: the :mod:`gc` module's :func:`is_tracked` returns true if a given instance is tracked by the garbage collector, false otherwise. (Contributed by Antoine Pitrou; :issue:`4688`.) @@ -419,6 +452,13 @@ changes, or look through the Subversion logs for all the details. (Implemented by Antoine Pitrou; :issue:`4444`.) + The methods :meth:`addCleanup` and :meth:`doCleanups` were added. + :meth:`addCleanup` allows you to add cleanup functions that + will be called unconditionally (after :meth:`setUp` if + :meth:`setUp` fails, otherwise after :meth:`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 @@ -473,6 +513,14 @@ changes, or look through the Subversion logs for all the details. to provide additional information about why the two objects are matching, much as the new sequence comparison methods do. + :func:`unittest.main` now takes an optional ``exit`` argument. + If False ``main`` doesn't call :func:`sys.exit` allowing it to + be used from the interactive interpreter. :issue:`3379`. + + :class:`TestResult` has new :meth:`startTestRun` and + :meth:`stopTestRun` methods; called immediately before + and after a test run. :issue:`5728` by Robert Collins. + * The :func:`is_zipfile` function in the :mod:`zipfile` module will now accept a file object, in addition to the path names accepted in earlier versions. (Contributed by Gabriel Genellina; :issue:`4756`.) @@ -553,6 +601,10 @@ Changes to Python's build process and to the C API include: is particularly useful for asynchronous IO operations. (Contributed by Kristjan Valur Jonsson; :issue:`4293`.) +* Global symbols defined by the :mod:`ctypes` module are now prefixed + with ``Py`, or with ``_ctypes``. (Implemented by Thomas + Heller; :issue:`3102`.) + * 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, @@ -591,10 +643,10 @@ Other Changes and Fixes * When importing a module from a :file:`.pyc` or :file:`.pyo` file with an existing :file:`.py` counterpart, the :attr:`co_filename` - attributes of all code objects if the original filename is obsolete, - which 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`.) + 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 |