[Python-3000-checkins] r67485 - python/branches/py3k/Doc/whatsnew/3.0.rst
guido.van.rossum
python-3000-checkins at python.org
Wed Dec 3 01:54:52 CET 2008
Author: guido.van.rossum
Date: Wed Dec 3 01:54:52 2008
New Revision: 67485
Log:
Another checkpoint.
Modified:
python/branches/py3k/Doc/whatsnew/3.0.rst
Modified: python/branches/py3k/Doc/whatsnew/3.0.rst
==============================================================================
--- python/branches/py3k/Doc/whatsnew/3.0.rst (original)
+++ python/branches/py3k/Doc/whatsnew/3.0.rst Wed Dec 3 01:54:52 2008
@@ -146,6 +146,9 @@
The change is for the better, as in the 2.x world there were
numerous bugs having to do with mixing encoded and unencoded text.
+* You no longer need to use ``u"..."`` literals for Unicode text.
+ However, you must use ``b"..."`` literals for binary data.
+
* Files opened as text files (still the default mode for :func:`open`)
always use an encoding to map between strings (in memory) and bytes
(on disk). Binary files (opened with a ``b`` in the mode argument)
@@ -174,7 +177,8 @@
* :class:`dict` methods :meth:`dict.keys`, :meth:`dict.items` and
:meth:`dict.values` return "views" instead of lists. For example,
this no longer works: ``k = d.keys(); k.sort()``. Use ``k =
- sorted(d)`` instead.
+ sorted(d)`` instead (this works in Python 2.5 too, and is just
+ as efficient).
* Also, the :meth:`dict.iterkeys`, :meth:`dict.iteritems` and
:meth:`dict.itervalues` methods are no longer supported.
@@ -185,13 +189,12 @@
Particularly tricky is :func:`map` invoked for the side effects of the
function; the correct transformation is to use a for-loop.
-* :func:`range` now behaves like :func:`xrange` used to behave.
- The latter no longer exists.
+* :func:`range` now behaves like :func:`xrange` used to behave, except
+ it works with values of arbitrary size. The latter no longer
+ exists.
* :func:`zip` now returns an iterator.
-* XXX More below?
-
Ordering Comparisons
--------------------
@@ -215,21 +218,20 @@
* The :func:`cmp` function is gone, and the :meth:`__cmp__` special
method is no longer supported. Use :meth:`__lt__` for sorting,
:meth:`__eq__` with :meth:`__hash__`, and other rich comparisons as
- needed. if you really need the :func:`cmp` functionality, the
- expression ``(a > b) - (a < b)`` is equivalent to ``cmp(a, b)``.
-
-* XXX More below?
+ needed. (If you really need the :func:`cmp` functionality, you
+ could use the expression ``(a > b) - (a < b)`` as the equivalent for
+ ``cmp(a, b)``.)
Integers
--------
-* :pep:`0237`: :class:`long` renamed to :class:`int`. That is, there
- is only one built-in integral type, named :class:`int`; but it
- behaves mostly like the old :class:`long` type.
-
-* The :func:`repr` of a long integer doesn't include the trailing ``L``
- anymore, so code that unconditionally strips that character will
- chop off the last digit instead. (Use :func:`str` instead.)
+* :pep:`0237`: Essentially, :class:`long` renamed to :class:`int`.
+ That is, there is only one built-in integral type, named
+ :class:`int`; but it behaves mostly like the old :class:`long` type.
+
+* :pep:`0238`: An expression like ``1/2`` returns a float. Use
+ ``1//2`` to get the truncating behavior. (The latter syntax has
+ existed for years, at least since Python 2.2.)
* The :data:`sys.maxint` constant was removed, since there is no
longer a limit to the value of ints. However, :data:`sys.maxsize`
@@ -238,20 +240,29 @@
and is typically the same as :data:`sys.maxint` in previous releases
on the same platform (assuming the same build options).
-* ``1/2`` returns a float. Use ``1//2`` to get the truncating behavior.
- (The latter syntax has existed for years, at least since Python 2.2.)
- See :pep:`0238`.
+* The :func:`repr` of a long integer doesn't include the trailing ``L``
+ anymore, so code that unconditionally strips that character will
+ chop off the last digit instead. (Use :func:`str` instead.)
+* Octal literals are no longer of the form ``0720``; use ``0o720``
+ instead.
-Overview Of Syntactic Changes
-=============================
-This section gives a brief overview of every *syntactic* change.
+Overview Of Syntax Changes
+==========================
+
+This section gives a brief overview of every *syntactic* change in
+Python 3.0.
Additions
---------
-* Function argument and return value annotations (see below). XXX
+* :pep:`3107`: Function argument and return value annotations. This
+ provides a standardized way of annotating a function's parameters
+ and return value. There are no semantics attached to such
+ annotations except that they can be introspected at runtime using
+ the :attr:`__annotations__` attribute. The intent is to encourage
+ experimentation through metaclasses, decorators or frameworks.
* :pep:`3102`: Keyword-only arguments. Named parameters occurring
after ``*args`` in the parameter list *must* be specified using
@@ -261,8 +272,8 @@
* Keyword arguments are allowed after the list of base classes in a
class definition. This is used by the new convention for specifying
- a metaclass, but can be used for other purposes as well, as long as
- the metaclass supports it.
+ a metaclass (see :pep:`3115`), but can be used for other purposes as
+ well, as long as the metaclass supports it.
* :pep:`3104`: :keyword:`nonlocal` statement. Using ``nonlocal x``
you can now assign directly to a variable in an outer (but
@@ -278,11 +289,12 @@
This sets *a* to ``0``, *b* to ``4``, and \*rest to ``[1, 2, 3]``.
* Dictionary comprehensions: ``{k: v for k, v in stuff}`` means the
- same thing as ``dict(stuff)`` but is more flexible.
+ same thing as ``dict(stuff)`` but is more flexible. (This is
+ :pep:`0274` vindicated. :-)
* Set literals, e.g. ``{1, 2}``. Note that ``{}`` is an empty
dictionary; use ``set()`` for an empty set. Set comprehensions are
- also supported; ``{x for x in stuff}`` means the same thing as
+ also supported; e.g., ``{x for x in stuff}`` means the same thing as
``set(stuff)`` but is more flexible.
* New octal literals, e.g. ``0o720`` (already in 2.6). The old octal
@@ -588,14 +600,6 @@
referred to as *dictionary views*.
-:pep:`3107`: Function Annotations
-=================================
-
-.. XXX expand this
-
-* A standardized way of annotating a function's parameters and return values.
-
-
Exception Stuff
===============
@@ -664,10 +668,6 @@
:exc:`EOFError` if the input is terminated prematurely. To get the
old behavior of :func:`input`, use ``eval(input())``.
-* :func:`xrange` renamed to :func:`range`, so :func:`range` will no
- longer produce a list but an iterable yielding integers when
- iterated over. XXX dupe
-
* :pep:`3114`: ``.next()`` renamed to :meth:`__next__`, new builtin
:func:`next` to call the :meth:`__next__` method on an object.
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