Another checkpoint.

This commit is contained in:
Guido van Rossum 2008-12-03 00:54:52 +00:00
parent f3655c439d
commit 7396135b90
1 changed files with 38 additions and 38 deletions

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@ -146,6 +146,9 @@ changes:
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 @@ Some well-known APIs no longer return lists:
* :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 @@ Some well-known APIs no longer return lists:
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 @@ Python 3.0 has simplified the rules for ordering comparisons:
* 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.
* :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.
* 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:`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 @@ Integers
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
=============================
Overview Of Syntax Changes
==========================
This section gives a brief overview of every *syntactic* change.
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 @@ Additions
* 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 @@ Additions
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 @@ This section discusses the many changes in string XXX
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 @@ Other Language Changes
: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.