2007-08-15 11:28:22 -03:00
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****************************
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2008-12-01 20:56:25 -04:00
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What's New In Python 3.0
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2007-08-15 11:28:22 -03:00
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****************************
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2008-11-21 14:35:43 -04:00
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.. XXX add trademark info for Apple, Microsoft, SourceForge.
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2008-12-01 20:56:25 -04:00
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.. XXX turn all PEP references into :pep:`NNN` markup.
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2007-09-01 16:26:28 -03:00
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:Author: Guido van Rossum
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2008-11-21 14:35:43 -04:00
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:Release: |release|
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:Date: |today|
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2007-08-31 03:15:01 -03:00
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2008-11-21 14:35:43 -04:00
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.. $Id$
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Rules for maintenance:
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2007-08-31 03:15:01 -03:00
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* Anyone can add text to this document. Do not spend very much time
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on the wording of your changes, because your text will probably
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get rewritten to some degree.
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* The maintainer will go through Misc/NEWS periodically and add
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changes; it's therefore more important to add your changes to
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Misc/NEWS than to this file.
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* This is not a complete list of every single change; completeness
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is the purpose of Misc/NEWS. Some changes I consider too small
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or esoteric to include. If such a change is added to the text,
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I'll just remove it. (This is another reason you shouldn't spend
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too much time on writing your addition.)
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* If you want to draw your new text to the attention of the
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maintainer, add 'XXX' to the beginning of the paragraph or
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section.
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* It's OK to just add a fragmentary note about a change. For
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example: "XXX Describe the transmogrify() function added to the
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socket module." The maintainer will research the change and
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write the necessary text.
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* You can comment out your additions if you like, but it's not
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necessary (especially when a final release is some months away).
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* Credit the author of a patch or bugfix. Just the name is
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sufficient; the e-mail address isn't necessary.
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* It's helpful to add the bug/patch number as a comment:
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% Patch 12345
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XXX Describe the transmogrify() function added to the socket
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module.
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(Contributed by P.Y. Developer.)
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This saves the maintainer the effort of going through the SVN log
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when researching a change.
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2007-08-15 11:28:22 -03:00
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2008-12-01 20:56:25 -04:00
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This article explains the new features in Python 3.0, compared to 2.6.
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Python 3.0 is the first ever *intentionally incompatible* release.
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There are more changes than in a typical release, and more that are
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important for all Python users. Nevertheless, after digesting the
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changes, you'll find that Python really hasn't changed all that much
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-- by and large, we're merely fixing well-known annoyances and warts.
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2007-08-30 21:37:00 -03:00
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This article doesn't attempt to provide a complete specification of
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the new features, but instead provides a convenient overview. For
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full details, you should refer to the documentation for Python 3.0. If
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you want to understand the complete implementation and design
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rationale, refer to the PEP for a particular new feature.
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2007-08-15 11:28:22 -03:00
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2007-08-31 03:15:01 -03:00
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.. Compare with previous release in 2 - 3 sentences here.
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.. add hyperlink when the documentation becomes available online.
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2007-08-15 11:28:22 -03:00
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2007-08-31 03:15:01 -03:00
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.. ======================================================================
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.. Large, PEP-level features and changes should be described here.
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.. Should there be a new section here for 3k migration?
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.. Or perhaps a more general section describing module changes/deprecation?
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.. sets module deprecated
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.. ======================================================================
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2007-08-15 11:28:22 -03:00
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2007-08-30 21:37:00 -03:00
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Common Stumbling Blocks
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=======================
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2008-12-01 20:56:25 -04:00
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This section briefly lists a few changes that are more likely to trip
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people up, without necessarily raising obvious errors. Most issues
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are explained in more detail in later sections.
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Print Is A Function
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-------------------
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The ``print`` statement has been replaced with a :func:`print` function,
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with keyword arguments to replace most of the special syntax of the
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old ``print`` statement (PEP 3105). Examples::
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Old: print "The answer is", 2*2
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New: print("The answer is", 2*2)
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Old: print x, # Trailing comma suppresses newline
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New: print(x, end=" ") # Appends a space instead of a newline
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Old: print # Prints a newline
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New: print() # You must call the function!
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Old: print >>sys.stderr, "fatal error"
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New: print("fatal error", file=sys.stderr)
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Old: print (x, y) # prints repr((x, y))
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New: print((x, y)) # Not the same as print(x, y)!
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You can also customize the separator between items, e.g.::
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print("There are <", 2**32, "> possibilities!", sep="")
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which produces::
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2007-08-30 21:37:00 -03:00
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2008-12-01 20:56:25 -04:00
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There are <4294967296> possibilities!
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2007-09-06 11:46:41 -03:00
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2008-12-01 20:56:25 -04:00
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Note:
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2007-09-06 11:46:41 -03:00
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2008-12-01 20:56:25 -04:00
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* The :func:`print` function doesn't support the "softspace" feature of
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the old ``print`` statement. For example, in Python 2.x,
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``print "A\n", "B"`` would write ``"A\nB\n"``; but in Python 3.0,
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``print("A\n", "B")`` writes ``"A\n B\n"``.
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2007-09-06 11:46:41 -03:00
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2008-12-01 20:56:25 -04:00
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* Initially, you'll be finding yourself typing the old ``print x``
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a lot in interactive mode. Time to retrain your fingers to type
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``print(x)`` instead!
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2007-09-06 11:46:41 -03:00
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2008-12-01 20:56:25 -04:00
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* When using the ``2to3`` source-to-source conversion tool, all
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``print`` statements are automatically converted to :func:`print`
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function calls, so this is mostly a non-issue for larger projects.
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2007-09-06 11:46:41 -03:00
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2008-12-01 20:56:25 -04:00
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Text Strings Vs. Bytes
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----------------------
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2007-09-06 11:46:41 -03:00
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2008-12-01 20:56:25 -04:00
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Everything you thought you knew about binary data and Unicode has
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changed:
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2007-09-06 11:46:41 -03:00
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2008-12-01 20:56:25 -04:00
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* Python 3.0 uses *strings* and *bytes* instead of *Unicode strings*
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and *8-bit strings*. The difference is that any attempt to mix
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strings and bytes in Python 3.0 raises a TypeError exception,
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whereas if you were to mix Unicode and 8-bit strings in Python 2.x,
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you would only get an exception if the 8-bit string contained
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non-ASCII values. As a consequence, pretty much all code that
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uses Unicode, encodings or binary data most likely has to change.
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The change is for the better, as in the 2.x world there were
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numerous bugs having to do with mixing encoded and unencoded text.
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2007-09-06 11:46:41 -03:00
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2008-12-01 20:56:25 -04:00
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* Files opened as text files (still the default mode for :func:`open`)
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always use an encoding to map between strings (in memory) and bytes
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(on disk). Binary files (opened with a ``b`` in the mode argument)
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always use bytes in memory. This means that if a file is opened
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using an incorrect mode or encoding, I/O will likely fail. There is
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a platform-dependent default encoding, which on Unixy platforms can
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be set with the ``LANG`` environment variable (and sometimes also
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with some other platform-specific locale-related environment
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variables). In many cases, but not all, the system default is
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2008-12-02 07:55:30 -04:00
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UTF-8; you should never count on this default. Any application
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2008-12-01 20:56:25 -04:00
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reading or writing more than pure ASCII text should probably have a
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way to override the encoding.
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2007-09-06 11:46:41 -03:00
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2008-12-01 20:56:25 -04:00
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* XXX More below?
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2007-09-06 11:46:41 -03:00
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2008-12-01 20:56:25 -04:00
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* See also the *Unicode HOWTO*. (XXX How to make this a link?)
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(XXX Move to longer section below?)
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2007-09-06 11:46:41 -03:00
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2008-12-01 20:56:25 -04:00
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Views And Interators Instead Of Lists
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-------------------------------------
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Some well-known APIs no longer return lists:
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* :class:`dict` methods :meth:`dict.keys`, :meth:`dict.items` and
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:meth:`dict.values` return "views" instead of lists. For example,
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this no longer works: ``k = d.keys(); k.sort()``. Use ``k =
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sorted(d)`` instead.
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* Also, the :meth:`dict.iterkeys`, :meth:`dict.iteritems` and
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:meth:`dict.itervalues` methods are no longer supported.
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* :func:`map` and :func:`filter` return iterators. A quick fix is e.g.
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``list(map(...))``, but a better fix is often to use a list
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comprehension (especially when the original code uses :keyword:`lambda`).
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Particularly tricky is :func:`map` invoked for the side effects of the
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function; the correct transformation is to use a for-loop.
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2007-09-06 11:46:41 -03:00
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2008-12-01 20:56:25 -04:00
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* :func:`range` now behaves like :func:`xrange` used to behave.
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The latter no longer exists.
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2007-09-06 11:46:41 -03:00
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2008-12-01 20:56:25 -04:00
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* :func:`zip` now returns an iterator.
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2007-09-06 11:46:41 -03:00
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2008-12-01 20:56:25 -04:00
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* XXX More below?
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2007-08-30 21:37:00 -03:00
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2008-12-01 20:56:25 -04:00
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Ordering Comparisons
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--------------------
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Python 3.0 has simplified the rules for ordering comparisons:
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2007-08-30 21:37:00 -03:00
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2008-11-21 14:35:43 -04:00
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* The ordering comparison operators (``<``, ``<=``, ``>=``, ``>``)
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raise a TypeError exception when the operands don't have a
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meaningful natural ordering. Thus, expressions like ``1 < ''``, ``0
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2008-12-01 20:56:25 -04:00
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> None`` or ``len <= len`` are no longer valid. A corollary is that
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2008-11-21 14:35:43 -04:00
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sorting a heterogeneous list no longer makes sense -- all the
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elements must be comparable to each other. Note that this does not
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apply to the ``==`` and ``!=`` operators: objects of different
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uncomparable types always compare unequal to each other, and an
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object always compares equal to itself (i.e., ``x is y`` implies ``x
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= y``; this is true even for ``NaN``).
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2008-02-13 14:03:11 -04:00
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* :meth:`builtin.sorted` and :meth:`list.sort` no longer accept the *cmp*
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2008-02-13 22:47:50 -04:00
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argument providing a comparison function. Use the *key* argument
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2008-02-13 14:03:11 -04:00
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instead. N.B. the *key* and *reverse* arguments are now "keyword-only".
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2008-02-13 12:09:27 -04:00
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2008-12-01 20:56:25 -04:00
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* The :func:`cmp` function is gone, and the :meth:`__cmp__` special
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method is no longer supported. Use :meth:`__lt__` for sorting,
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:meth:`__eq__` with :meth:`__hash__`, and other rich comparisons as
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needed. if you really need the :func:`cmp` functionality, the
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expression ``(a > b) - (a < b)`` is equivalent to ``cmp(a, b)``.
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2008-11-22 04:35:59 -04:00
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2008-12-01 20:56:25 -04:00
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* XXX More below?
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2007-08-30 21:37:00 -03:00
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2008-12-01 20:56:25 -04:00
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Integers
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--------
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* We unified the :class:`int` and :class:`long` types. All integers
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are now of type :class:`int`.
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* ``1/2`` returns a float. Use ``1//2`` to get the truncating behavior.
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(The latter syntax has existed for years, at least since Python 2.2.)
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2008-11-21 14:35:43 -04:00
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2008-02-02 06:44:37 -04:00
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* The :func:`repr` of a long integer doesn't include the trailing ``L``
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2007-12-09 05:04:01 -04:00
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anymore, so code that unconditionally strips that character will
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chop off the last digit instead.
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2007-08-30 21:37:00 -03:00
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2008-12-01 20:56:25 -04:00
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* The :data:`sys.maxint` constant was removed, since there is no
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longer a limit to the value of ints. However, :data:`sys.maxsize`
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can be used as an integer larger than any practical list or string
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index. It conforms to the implementation's "natural" integer size
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and is typically the same as :data:`sys.maxint` in previous releases
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on the same platform (assuming the same build options).
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* XXX More below?
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Overview Of Syntactic Changes
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=============================
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This section gives a brief overview of every *syntactic* change.
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Several of these are discussed at greater length later.
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XXX Did I get everything?
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Additions
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---------
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2007-08-30 21:37:00 -03:00
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2008-12-01 20:56:25 -04:00
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* Function argument and return value annotations (see below). XXX
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* A lone ``*`` in a formal parameter list implies that any following
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arguments *must* be specified in keyword form. (XXX Didn't this make
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it into 2.6 as well?)
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* Keyword arguments are allowed after the list of base classes in a
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class definition. This is used by the new convention for specifying
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a metaclass, but can be used for other purposes as well, as long as
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the metaclass supports it.
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* Tuple-unpacking assignment now has a *wildcard* syntax, e.g.::
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(a, b, *rest) = range(5)
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2008-12-01 21:12:04 -04:00
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This sets *a* to 0, *b* to 1, and \*rest to ``[2, 3, 4]``.
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2008-12-01 20:56:25 -04:00
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* Dictionary comprehensions: ``{k: v for k, v in stuff}`` means the
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same thing as ``dict(stuff)`` but is more flexible.
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* Set literals, e.g. ``{1, 2}``. Note that ``{}`` is an empty
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dictionary; use ``set()`` for an empty set. Set comprehensions
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are also supported; ``{x for x in stuff}`` means the same thing
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as ``set(stuff)`` but is more flexible.
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* New octal literals, e.g. ``0o720`` (already in 2.6). The old octal
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literals (``0720`` are gone.
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* New binary literals, e.g. ``0b1010`` (already in 2.6).
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* Bytes literals are introduced with a leading ``b`` or ``B``.
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Changes
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-------
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* New :keyword:`raise` statement syntax: ``raise [expr [from expr]]``.
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* New keywords: :keyword:`as`, :keyword:`with` (already in 2.6),
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:keyword:`None` (partially enforced in 2.6), :keyword:`True`,
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:keyword:`False` (these were built-ins previously), and
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:keyword:`nonlocal` (for the new ``nonlocal`` statement).
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* Change from ``except exc, var:`` to ``except exc as var:``. XXX
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* *Very* subtle changes in the syntax for list comprehensions,
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generator expressions, :keyword:`lambda expression and :keyword:`if`
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expressions. For example, this is valid in Python 2.6::
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[ x for x in lambda: True, lambda: False if x() ]
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In Python 3.0 you'll have to add parentheses, like this::
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[ x for x in (lambda: True, lambda: False) if x() ]
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* The *ellipsis* (``...``) can be used as an atomic expression anywhere.
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|
(Previously it was only allowed in slices.)
|
|
|
|
|
|
|
|
Removals
|
|
|
|
--------
|
|
|
|
|
|
|
|
* Tuple parameter unpacking removed. XXX
|
|
|
|
|
|
|
|
* Removal of backticks. XXX
|
|
|
|
|
|
|
|
* Removal of ``<>``. Use ``!=`` instead. XXX
|
|
|
|
|
|
|
|
* Removed keyword: :func:`exec` is no longer a keyword; it remains as
|
|
|
|
a function. (Fortunately the function syntax was also accepted in
|
|
|
|
2.x.)
|
|
|
|
|
|
|
|
* Integer literals no longer support a trailing ``l`` or ``L``.
|
|
|
|
|
|
|
|
* String literals no longer support a leading ``u`` or ``U``.
|
|
|
|
|
|
|
|
* The *ellipsis* must now be spelled as ``...``; previously it could
|
|
|
|
(by a mere accident of the grammar) also be spelled as ``. . .``.
|
|
|
|
|
|
|
|
|
|
|
|
Changes Already Present In Python 2.6
|
|
|
|
=====================================
|
|
|
|
|
|
|
|
This section reminds the reader of new features that were originally
|
|
|
|
designed for Python 3.0 but that were already introduced in Python
|
|
|
|
2.6. The descriptions in "What's New in Python 2.6" are hereby
|
|
|
|
included by reference.
|
|
|
|
|
|
|
|
* XXX List each of those briefly.
|
|
|
|
|
|
|
|
Strings And Bytes
|
2007-08-30 21:37:00 -03:00
|
|
|
=================
|
|
|
|
|
2008-12-01 20:56:25 -04:00
|
|
|
This section discusses the many changes in string
|
|
|
|
|
2008-02-02 06:44:37 -04:00
|
|
|
* There is only one string type; its name is :class:`str` but its behavior and
|
|
|
|
implementation are like :class:`unicode` in 2.x.
|
2007-08-30 21:37:00 -03:00
|
|
|
|
2008-02-02 06:44:37 -04:00
|
|
|
* The :class:`basestring` superclass has been removed. The ``2to3`` tool
|
2008-07-22 16:27:12 -03:00
|
|
|
replaces every occurrence of :class:`basestring` with :class:`str`.
|
2008-01-25 07:02:28 -04:00
|
|
|
|
2008-02-02 06:44:37 -04:00
|
|
|
* PEP 3137: There is a new type, :class:`bytes`, to represent binary data (and
|
|
|
|
encoded text, which is treated as binary data until you decide to decode it).
|
|
|
|
The :class:`str` and :class:`bytes` types cannot be mixed; you must always
|
|
|
|
explicitly convert between them, using the :meth:`str.encode` (str -> bytes)
|
|
|
|
or :meth:`bytes.decode` (bytes -> str) methods.
|
2007-08-30 21:37:00 -03:00
|
|
|
|
2008-04-28 18:05:10 -03:00
|
|
|
* All backslashes in raw strings are interpreted literally. This means that
|
2008-11-21 14:35:43 -04:00
|
|
|
``'\U'`` and ``'\u'`` escapes in raw strings are not treated specially.
|
2008-04-28 18:05:10 -03:00
|
|
|
|
2008-02-02 06:44:37 -04:00
|
|
|
.. XXX add bytearray
|
|
|
|
|
|
|
|
* PEP 3112: Bytes literals, e.g. ``b"abc"``, create :class:`bytes` instances.
|
2007-08-30 21:37:00 -03:00
|
|
|
|
|
|
|
* PEP 3120: UTF-8 default source encoding.
|
|
|
|
|
2008-02-02 06:44:37 -04:00
|
|
|
* PEP 3131: Non-ASCII identifiers. (However, the standard library remains
|
|
|
|
ASCII-only with the exception of contributor names in comments.)
|
2007-08-30 21:37:00 -03:00
|
|
|
|
|
|
|
* PEP 3116: New I/O Implementation. The API is nearly 100% backwards
|
2008-02-02 06:44:37 -04:00
|
|
|
compatible, but completely reimplemented (currently mostly in Python). Also,
|
|
|
|
binary files use bytes instead of strings.
|
2007-08-30 21:37:00 -03:00
|
|
|
|
2008-02-02 06:44:37 -04:00
|
|
|
* The :mod:`StringIO` and :mod:`cStringIO` modules are gone. Instead, import
|
|
|
|
:class:`io.StringIO` or :class:`io.BytesIO`.
|
2007-08-30 21:37:00 -03:00
|
|
|
|
2008-04-28 18:05:10 -03:00
|
|
|
|
2007-08-30 21:37:00 -03:00
|
|
|
|
2008-12-01 20:56:25 -04:00
|
|
|
PEP 3101: A New Approach To String Formatting
|
2007-08-30 21:37:00 -03:00
|
|
|
=============================================
|
|
|
|
|
2008-11-21 14:35:43 -04:00
|
|
|
* A new system for built-in string formatting operations replaces the
|
|
|
|
``%`` string formatting operator. (However, the ``%`` operator is
|
|
|
|
still supported; it will be deprecated in Python 3.1 and removed
|
|
|
|
from the language at some later time.)
|
2007-08-30 21:37:00 -03:00
|
|
|
|
2008-11-21 14:35:43 -04:00
|
|
|
.. XXX expand this
|
2007-08-30 21:37:00 -03:00
|
|
|
|
|
|
|
|
2008-02-02 06:44:37 -04:00
|
|
|
PEP 3106: Revamping dict :meth:`dict.keys`, :meth:`dict.items` and :meth:`dict.values`
|
|
|
|
======================================================================================
|
2008-02-02 06:30:18 -04:00
|
|
|
|
2008-12-01 20:56:25 -04:00
|
|
|
.. XXX expand this (but note that the "pitfalls" section currently has
|
|
|
|
.. XXX more detail :-)
|
2008-02-02 06:30:18 -04:00
|
|
|
|
2008-02-02 06:44:37 -04:00
|
|
|
* The :meth:`dict.iterkeys`, :meth:`dict.itervalues` and :meth:`dict.iteritems`
|
|
|
|
methods have been removed.
|
2008-02-02 06:30:18 -04:00
|
|
|
|
2008-02-02 06:44:37 -04:00
|
|
|
* :meth:`dict.keys`, :meth:`dict.values` and :meth:`dict.items` return objects
|
2008-11-21 14:35:43 -04:00
|
|
|
with set behavior that reference the underlying dict; these are often
|
|
|
|
referred to as *dictionary views*.
|
2007-08-30 21:37:00 -03:00
|
|
|
|
|
|
|
|
|
|
|
PEP 3107: Function Annotations
|
|
|
|
==============================
|
|
|
|
|
2008-02-02 06:30:18 -04:00
|
|
|
.. XXX expand this
|
|
|
|
|
2008-02-02 06:44:37 -04:00
|
|
|
* A standardized way of annotating a function's parameters and return values.
|
2007-08-30 21:37:00 -03:00
|
|
|
|
|
|
|
|
|
|
|
Exception Stuff
|
|
|
|
===============
|
|
|
|
|
2008-12-01 20:56:25 -04:00
|
|
|
* PEP 352: All exceptions must be derived (directly or indirectly)
|
|
|
|
from :exc:`BaseException`. This is the root of the exception
|
|
|
|
hierarchy. Most exceptions should actually be derived from
|
|
|
|
:exc:`Exception`. This is not a new recommendation, but the
|
|
|
|
*requirement* to inherit from :exc:`BaseException` is new. (Python
|
|
|
|
2.6 still allowed classic classes to be raised, and placed no
|
|
|
|
restriction on what you can catch.)
|
2007-08-30 21:37:00 -03:00
|
|
|
|
2008-12-01 20:56:25 -04:00
|
|
|
* :exc:`StandardError` was removed (in 2.6, actually).
|
2007-08-30 21:37:00 -03:00
|
|
|
|
2008-02-02 06:44:37 -04:00
|
|
|
* Dropping sequence behavior (slicing!) and :attr:`message` attribute of
|
2007-08-31 03:15:01 -03:00
|
|
|
exception instances.
|
2007-08-30 21:37:00 -03:00
|
|
|
|
2008-02-02 06:44:37 -04:00
|
|
|
* PEP 3109: Raising exceptions. You must now use ``raise Exception(args)``
|
|
|
|
instead of ``raise Exception, args``.
|
2007-08-30 21:37:00 -03:00
|
|
|
|
2008-05-05 18:42:51 -03:00
|
|
|
* PEP 3110: Catching exceptions. You must now use ``except SomeException as
|
|
|
|
identifier:`` instead of ``except Exception, identifier:``
|
2007-08-30 21:37:00 -03:00
|
|
|
|
2008-12-01 20:56:25 -04:00
|
|
|
* PEP 3134: Exception chaining.
|
2007-08-30 21:37:00 -03:00
|
|
|
|
2008-02-02 06:44:37 -04:00
|
|
|
* A few exception messages are improved when Windows fails to load an extension
|
|
|
|
module. For example, ``error code 193`` is now ``%1 is not a valid Win32
|
|
|
|
application``. Strings now deal with non-English locales.
|
2008-02-02 06:30:18 -04:00
|
|
|
|
2007-08-30 21:37:00 -03:00
|
|
|
|
2008-12-01 20:56:25 -04:00
|
|
|
New Class And Metaclass Stuff
|
2007-08-30 21:37:00 -03:00
|
|
|
=============================
|
|
|
|
|
|
|
|
* Classic classes are gone.
|
|
|
|
|
|
|
|
* PEP 3115: New Metaclass Syntax.
|
|
|
|
|
2007-09-03 23:48:01 -03:00
|
|
|
* PEP 3119: Abstract Base Classes (ABCs); ``@abstractmethod`` and
|
2007-08-30 21:37:00 -03:00
|
|
|
``@abstractproperty`` decorators; collection ABCs.
|
|
|
|
|
|
|
|
* PEP 3129: Class decorators.
|
|
|
|
|
|
|
|
* PEP 3141: Numeric ABCs.
|
|
|
|
|
|
|
|
|
2007-08-15 11:28:22 -03:00
|
|
|
Other Language Changes
|
|
|
|
======================
|
|
|
|
|
2007-08-30 21:37:00 -03:00
|
|
|
Here are most of the changes that Python 3.0 makes to the core Python
|
|
|
|
language and built-in functions.
|
|
|
|
|
2008-02-02 06:44:37 -04:00
|
|
|
* Removed backticks (use :func:`repr` instead).
|
2007-08-30 21:37:00 -03:00
|
|
|
|
|
|
|
* Removed ``<>`` (use ``!=`` instead).
|
|
|
|
|
2008-02-02 06:30:18 -04:00
|
|
|
* ``!=`` now returns the opposite of ``==``, unless ``==`` returns
|
|
|
|
``NotImplemented``.
|
|
|
|
|
2008-02-02 06:44:37 -04:00
|
|
|
* :keyword:`as` and :keyword:`with` are keywords.
|
2007-08-30 21:37:00 -03:00
|
|
|
|
2008-02-02 06:30:18 -04:00
|
|
|
* ``True``, ``False``, and ``None`` are keywords.
|
|
|
|
|
2008-02-02 06:44:37 -04:00
|
|
|
* PEP 237: :class:`long` renamed to :class:`int`. That is, there is only one
|
|
|
|
built-in integral type, named :class:`int`; but it behaves like the old
|
|
|
|
:class:`long` type, with the exception that the literal suffix ``L`` is
|
|
|
|
neither supported by the parser nor produced by :func:`repr` anymore.
|
|
|
|
:data:`sys.maxint` was also removed since the int type has no maximum value
|
2008-12-01 20:56:25 -04:00
|
|
|
anymore. Use :data:`sys.maxsize` instead.
|
|
|
|
XXX Is this a dupe from the intro section on integers?
|
2007-08-30 21:37:00 -03:00
|
|
|
|
|
|
|
* PEP 238: int division returns a float.
|
|
|
|
|
2008-02-02 06:44:37 -04:00
|
|
|
* The ordering operators behave differently: for example, ``x < y`` where ``x``
|
|
|
|
and ``y`` have incompatible types raises :exc:`TypeError` instead of returning
|
|
|
|
a pseudo-random boolean.
|
2007-08-30 21:37:00 -03:00
|
|
|
|
2008-02-02 06:44:37 -04:00
|
|
|
* :meth:`__getslice__` and friends killed. The syntax ``a[i:j]`` now translates
|
|
|
|
to ``a.__getitem__(slice(i, j))`` (or :meth:`__setitem__` or
|
|
|
|
:meth:`__delitem__`, depending on context).
|
2007-08-30 21:37:00 -03:00
|
|
|
|
2008-02-02 06:44:37 -04:00
|
|
|
* PEP 3102: Keyword-only arguments. Named parameters occurring after ``*args``
|
|
|
|
in the parameter list *must* be specified using keyword syntax in the call.
|
|
|
|
You can also use a bare ``*`` in the parameter list to indicate that you don't
|
|
|
|
accept a variable-length argument list, but you do have keyword-only
|
|
|
|
arguments.
|
2007-08-30 21:37:00 -03:00
|
|
|
|
2008-02-02 06:44:37 -04:00
|
|
|
* PEP 3104: :keyword:`nonlocal` statement. Using ``nonlocal x`` you can now
|
2007-08-30 21:37:00 -03:00
|
|
|
assign directly to a variable in an outer (but non-global) scope.
|
|
|
|
|
2008-02-02 06:44:37 -04:00
|
|
|
* PEP 3111: :func:`raw_input` renamed to :func:`input`. That is, the new
|
|
|
|
:func:`input` function reads a line from :data:`sys.stdin` and returns it with
|
|
|
|
the trailing newline stripped. It raises :exc:`EOFError` if the input is
|
|
|
|
terminated prematurely. To get the old behavior of :func:`input`, use
|
|
|
|
``eval(input())``.
|
2007-08-30 21:37:00 -03:00
|
|
|
|
2008-04-09 04:32:07 -03:00
|
|
|
* :func:`xrange` renamed to :func:`range`, so :func:`range` will no longer
|
|
|
|
produce a list but an iterable yielding integers when iterated over.
|
2007-08-30 21:37:00 -03:00
|
|
|
|
2008-02-02 06:44:37 -04:00
|
|
|
* PEP 3113: Tuple parameter unpacking removed. You can no longer write ``def
|
|
|
|
foo(a, (b, c)): ...``. Use ``def foo(a, b_c): b, c = b_c`` instead.
|
2007-08-30 21:37:00 -03:00
|
|
|
|
2008-02-02 06:44:37 -04:00
|
|
|
* PEP 3114: ``.next()`` renamed to :meth:`__next__`, new builtin :func:`next` to
|
|
|
|
call the :meth:`__next__` method on an object.
|
2007-08-30 21:37:00 -03:00
|
|
|
|
2008-02-02 06:44:37 -04:00
|
|
|
* PEP 3127: New octal literals; binary literals and :func:`bin`. Instead of
|
|
|
|
``0666``, you write ``0o666``. The :func:`oct` function is modified
|
|
|
|
accordingly. Also, ``0b1010`` equals 10, and ``bin(10)`` returns
|
|
|
|
``"0b1010"``. ``0666`` is now a :exc:`SyntaxError`.
|
2007-08-30 21:37:00 -03:00
|
|
|
|
2008-02-02 06:44:37 -04:00
|
|
|
* PEP 3132: Extended Iterable Unpacking. You can now write things like ``a, b,
|
|
|
|
*rest = some_sequence``. And even ``*rest, a = stuff``. The ``rest`` object
|
|
|
|
is always a list; the right-hand side may be any iterable.
|
2007-08-30 21:37:00 -03:00
|
|
|
|
2008-02-02 06:44:37 -04:00
|
|
|
* PEP 3135: New :func:`super`. You can now invoke :func:`super` without
|
|
|
|
arguments and the right class and instance will automatically be chosen. With
|
|
|
|
arguments, its behavior is unchanged.
|
2007-08-30 21:37:00 -03:00
|
|
|
|
2008-02-02 06:44:37 -04:00
|
|
|
* :func:`zip`, :func:`map` and :func:`filter` return iterators.
|
2007-08-30 21:37:00 -03:00
|
|
|
|
2008-02-02 06:44:37 -04:00
|
|
|
* :data:`string.letters` and its friends (:data:`string.lowercase` and
|
|
|
|
:data:`string.uppercase`) are gone. Use :data:`string.ascii_letters`
|
2007-08-30 21:37:00 -03:00
|
|
|
etc. instead.
|
|
|
|
|
2008-02-02 06:44:37 -04:00
|
|
|
* Removed: :func:`apply`, :func:`callable`, :func:`coerce`, :func:`execfile`,
|
|
|
|
:func:`file`, :func:`reduce`, :func:`reload`.
|
2007-08-30 21:37:00 -03:00
|
|
|
|
2008-02-18 18:20:55 -04:00
|
|
|
* Removed: :meth:`dict.has_key` -- use the ``in`` operator instead.
|
2007-08-15 11:28:22 -03:00
|
|
|
|
2008-02-02 06:44:37 -04:00
|
|
|
* :func:`exec` is now a function.
|
2008-02-02 06:30:18 -04:00
|
|
|
|
2008-02-02 06:44:37 -04:00
|
|
|
* The :meth:`__oct__` and :meth:`__hex__` special methods are removed --
|
|
|
|
:func:`oct` and :func:`hex` use :meth:`__index__` now to convert the argument
|
|
|
|
to an integer.
|
2008-02-02 06:30:18 -04:00
|
|
|
|
2008-02-02 06:44:37 -04:00
|
|
|
* Support is removed for :attr:`__members__` and :attr:`__methods__`.
|
2008-02-02 06:30:18 -04:00
|
|
|
|
2008-02-02 06:44:37 -04:00
|
|
|
* Renamed the boolean conversion C-level slot and method: ``nb_nonzero`` is now
|
|
|
|
``nb_bool`` and :meth:`__nonzero__` is now :meth:`__bool__`.
|
2008-02-02 06:30:18 -04:00
|
|
|
|
2007-08-15 11:28:22 -03:00
|
|
|
|
2007-08-31 03:15:01 -03:00
|
|
|
.. ======================================================================
|
2007-08-15 11:28:22 -03:00
|
|
|
|
|
|
|
|
|
|
|
Optimizations
|
|
|
|
-------------
|
|
|
|
|
|
|
|
* Detailed changes are listed here.
|
|
|
|
|
2008-12-01 20:56:25 -04:00
|
|
|
The net result of the 3.0 generalizations is that Python 3.0 runs the
|
|
|
|
pystone benchmark around a third slower than Python 2.5. There's room
|
|
|
|
for improvement, but it will happen after 3.0 is released!
|
2007-08-15 11:28:22 -03:00
|
|
|
|
2007-08-31 03:15:01 -03:00
|
|
|
.. ======================================================================
|
2007-08-15 11:28:22 -03:00
|
|
|
|
|
|
|
|
2008-12-01 20:56:25 -04:00
|
|
|
New, Improved, And Deprecated Modules
|
2007-08-15 11:28:22 -03:00
|
|
|
=====================================
|
|
|
|
|
2008-02-02 06:44:37 -04:00
|
|
|
As usual, 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.
|
2007-08-15 11:28:22 -03:00
|
|
|
|
2008-02-02 06:44:37 -04:00
|
|
|
* The :mod:`cPickle` module is gone. Use :mod:`pickle` instead. Eventually
|
2007-08-30 21:37:00 -03:00
|
|
|
we'll have a transparent accelerator module.
|
2007-08-15 11:28:22 -03:00
|
|
|
|
2008-02-02 06:44:37 -04:00
|
|
|
* The :mod:`imageop` module is gone.
|
2008-02-02 06:30:18 -04:00
|
|
|
|
2008-02-02 06:44:37 -04:00
|
|
|
* The :mod:`audiodev`, :mod:`Bastion`, :mod:`bsddb185`, :mod:`exceptions`,
|
|
|
|
:mod:`linuxaudiodev`, :mod:`md5`, :mod:`MimeWriter`, :mod:`mimify`,
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:mod:`popen2`, :mod:`rexec`, :mod:`sets`, :mod:`sha`, :mod:`stringold`,
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:mod:`strop`, :mod:`sunaudiodev`, :mod:`timing`, and :mod:`xmllib` modules are
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gone.
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2008-02-02 06:30:18 -04:00
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2008-09-04 02:07:03 -03:00
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* The :mod:`bsddb` module is gone. It is being maintained externally
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with its own release schedule better mirroring that of BerkeleyDB.
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See http://www.jcea.es/programacion/pybsddb.htm.
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2008-02-02 06:44:37 -04:00
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* The :mod:`new` module is gone.
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2008-02-02 06:30:18 -04:00
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2008-02-02 06:44:37 -04:00
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* The functions :func:`os.tmpnam`, :func:`os.tempnam` and :func:`os.tmpfile`
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have been removed in favor of the :mod:`tempfile` module.
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2008-02-02 06:30:18 -04:00
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2008-03-18 19:41:35 -03:00
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* The :mod:`tokenize` module has been changed to work with bytes. The main
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entry point is now :func:`tokenize.tokenize`, instead of generate_tokens.
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2007-08-31 03:15:01 -03:00
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.. ======================================================================
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.. whole new modules get described in subsections here
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2007-08-15 11:28:22 -03:00
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2007-08-31 03:15:01 -03:00
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.. ======================================================================
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2007-08-15 11:28:22 -03:00
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2008-12-01 20:56:25 -04:00
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Build And C API Changes
|
2007-08-15 11:28:22 -03:00
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|
=======================
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Changes to Python's build process and to the C API include:
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2007-08-30 21:37:00 -03:00
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* PEP 3118: New Buffer API.
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* PEP 3121: Extension Module Initialization & Finalization.
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|
2008-02-02 06:44:37 -04:00
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* PEP 3123: Making :cmacro:`PyObject_HEAD` conform to standard C.
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2007-08-15 11:28:22 -03:00
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|
2008-02-02 06:30:18 -04:00
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* No more C API support for restricted execution.
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|
2008-02-02 06:44:37 -04:00
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* :cfunc:`PyNumber_Coerce`, :cfunc:`PyNumber_CoerceEx`, :cfunc:`PyMember_Get`,
|
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|
and :cfunc:`PyMember_Set` C APIs are removed.
|
2008-02-02 06:30:18 -04:00
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|
2008-02-02 06:44:37 -04:00
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|
* New C API :cfunc:`PyImport_ImportModuleNoBlock`, works like
|
|
|
|
:cfunc:`PyImport_ImportModule` but won't block on the import lock (returning
|
2008-02-02 06:30:18 -04:00
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|
|
an error instead).
|
|
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|
2007-08-31 03:15:01 -03:00
|
|
|
.. ======================================================================
|
2007-08-15 11:28:22 -03:00
|
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|
|
Port-Specific Changes
|
|
|
|
---------------------
|
|
|
|
|
|
|
|
Platform-specific changes go here.
|
|
|
|
|
2008-02-02 06:30:18 -04:00
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|
2007-08-31 03:15:01 -03:00
|
|
|
.. ======================================================================
|
2007-08-15 11:28:22 -03:00
|
|
|
|
|
|
|
|
2008-10-10 21:49:57 -03:00
|
|
|
.. _30section-other:
|
2007-08-15 11:28:22 -03:00
|
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|
2008-12-01 20:56:25 -04:00
|
|
|
Other Changes And Fixes
|
2007-08-15 11:28:22 -03:00
|
|
|
=======================
|
|
|
|
|
2007-08-30 21:37:00 -03:00
|
|
|
As usual, there were a bunch of other improvements and bugfixes
|
|
|
|
scattered throughout the source tree. A search through the change
|
|
|
|
logs finds there were XXX patches applied and YYY bugs fixed between
|
|
|
|
Python 2.6 and 3.0. Both figures are likely to be underestimates.
|
2007-08-15 11:28:22 -03:00
|
|
|
|
|
|
|
Some of the more notable changes are:
|
|
|
|
|
|
|
|
* Details go here.
|
|
|
|
|
2007-08-31 03:15:01 -03:00
|
|
|
.. ======================================================================
|
2007-08-15 11:28:22 -03:00
|
|
|
|
|
|
|
|
2008-12-01 20:56:25 -04:00
|
|
|
Porting To Python 3.0
|
2007-08-15 11:28:22 -03:00
|
|
|
=====================
|
|
|
|
|
2007-08-30 21:37:00 -03:00
|
|
|
This section lists previously described changes that may require
|
|
|
|
changes to your code:
|
2007-08-15 11:28:22 -03:00
|
|
|
|
|
|
|
* Everything is all in the details!
|
|
|
|
|
2008-01-20 06:59:44 -04:00
|
|
|
* Developers can include :file:`intobject.h` after :file:`Python.h` for
|
|
|
|
some ``PyInt_`` aliases.
|
2007-12-02 12:52:32 -04:00
|
|
|
|
2008-12-01 20:56:25 -04:00
|
|
|
* XXX Mention 2to3.
|
2007-08-15 11:28:22 -03:00
|
|
|
|
2008-12-01 20:56:25 -04:00
|
|
|
* XXX Reference external doc about porting extensions?
|
2007-08-15 11:28:22 -03:00
|
|
|
|
2008-12-01 20:56:25 -04:00
|
|
|
.. ======================================================================
|