diff options
Diffstat (limited to 'Doc/whatsnew/whatsnew20.tex')
-rw-r--r-- | Doc/whatsnew/whatsnew20.tex | 233 |
1 files changed, 233 insertions, 0 deletions
diff --git a/Doc/whatsnew/whatsnew20.tex b/Doc/whatsnew/whatsnew20.tex new file mode 100644 index 0000000..5ce69f7 --- /dev/null +++ b/Doc/whatsnew/whatsnew20.tex @@ -0,0 +1,233 @@ +\documentclass{howto} + +\title{What's New in Python 1.6} +\release{0.01} +\author{A.M. Kuchling} +\authoraddress{\email{amk1@bigfoot.com}} +\begin{document} +\maketitle\tableofcontents + +\section{Introduction} + +A new release of Python, version 1.6, will be released some time this +summer. Alpha versions are already available from +\url{http://www.python.org/1.6/}. This article talks about the +exciting new features in 1.6, highlights some useful new features, and +points out a few incompatible changes that may require rewriting code. + +Python's development never ceases, and a steady flow of bug fixes and +improvements are always being submitted. A host of minor bug-fixes, a +few optimizations, additional docstrings, and better error messages +went into 1.6; to list them all would be impossible, but they're +certainly significant. Consult the publicly-available CVS logs if you +want to see the full list. + +% ====================================================================== +\section{Unicode} + +XXX + +unicode support: Unicode strings are marked with u"string", and there +is support for arbitrary encoders/decoders + +Added -U command line option. With the option enabled the Python +compiler interprets all "..." strings as u"..." (same with r"..." and +ur"..."). (Is this just for experimenting?) + + +% ====================================================================== +\section{Distribution Utilities} + +XXX + +% ====================================================================== +\section{String Methods} + +% ====================================================================== +\section{Porting to 1.6} + +New Python releases try hard to be compatible with previous releases, +and the record has been pretty good. However, some changes are +considered useful enough (often fixing design decisions that were +initially bad) that breaking backward compatibility in subtle ways +can't always be avoided. This section lists the changes in Python 1.6 +that may cause old Python code to break. + +The change which will probably break the most code is tightening up +the arguments accepted by some methods. Some methods would take +multiple arguments and treat them as a tuple, particularly various +list methods such as \method{.append()}, \method{.insert()}, +\method{remove()}, and \method{.count()}. +% +% XXX did anyone ever call the last 2 methods with multiple args? +% +In earlier versions of Python, if \code{L} is a list, \code{L.append( +1,2 )} appends the tuple \code{(1,2)} to the list. In Python 1.6 this +causes a \exception{TypeError} exception to be raised, with the +message: 'append requires exactly 1 argument; 2 given'. The fix is to +simply add an extra set of parentheses to pass both values as a tuple: +\code{L.append( (1,2) )}. + +The earlier versions of these methods were more forgiving because they +used an old function in Python's C interface to parse their arguments; +1.6 modernizes them to use \function{PyArg_ParseTuple}, the current +argument parsing function, which provides more helpful error messages +and treats multi-argument calls as errors. If you absolutely must use +1.6 but can't fix your code, you can edit \file{Objects/listobject.c} +and define the preprocessor symbol \code{NO_STRICT_LIST_APPEND} to +preserve the old behaviour; this isn't recommended. + +Some of the functions in the \module{socket} module are still +forgiving in this way. For example, \function{socket.connect( +('hostname', 25) )} is the correct form, passing a tuple representing +an IP address, but +\function{socket.connect( 'hostname', 25 )} also +works. \function{socket.connect_ex()} and \function{socket.bind()} are +similarly easy-going. 1.6alpha1 tightened these functions up, but +because the documentation actually used the erroneous multiple +argument form, many people wrote code which will break. So for +the\module{socket} module, the documentation was fixed and the +multiple argument form is simply marked as deprecated; it'll be +removed in a future Python version. + +Some work has been done to make integers and long integers a bit more +interchangeable. In 1.5.2, large-file support was added for Solaris, +to allow reading files larger than 2Gb; this made the \method{tell()} +method of file objects return a long integer instead of a regular +integer. Some code would subtract two file offsets and attempt to use +the result to multiply a sequence or slice a string, but this raised a +\exception{TypeError}. In 1.6, long integers can be used to multiply +or slice a sequence, and it'll behave as you'd intuitively expect it to; +\code{3L * 'abc'} produces 'abcabcabc', and +\code{ (0,1,2,3)[2L:4L]} produces (2,3). Long integers can also be +used in various new places where previously only integers were +accepted, such as in the \method{seek()} method of file objects. + +The subtlest long integer change of all is that the \function{str()} +of a long integer no longer has a trailing 'L' character, though +\function{repr()} still includes it. The 'L' annoyed many people who +wanted to print long integers that looked just like regular integers, +since they had to go out of their way to chop off the character. This +is no longer a problem in 1.6, but code which assumes the 'L' is +there, and does \code{str(longval)[:-1]} will now lose the final +digit. + +Taking the \function{repr()} of a float now uses a different +formatting precision than \function{str()}. \function{repr()} uses +``%.17g'' format string for C's \function{sprintf()}, while +\function{str()} uses ``%.12g'' as before. The effect is that +\function{repr()} may occasionally show more decimal places than +\function{str()}, for numbers +XXX need example value here. + + +% ====================================================================== +\section{Core Changes} + +Deleting objects is safe even for deeply nested data structures. +Comparing recursive objects is now safe (doesn't dump core). + +Builds on NT Alpha, and work on Win64 (NT Itanium -- sys.platform is +still 'win32') is ongoing. Supports Windows CE (confirm with Mark +Hammond) + +UnboundLocalError is raised when a local variable is undefined +long, int take optional "base" parameter + +string objects now have methods (though they are still immutable) + +sys.version_info is a tuple: (major, minor, micro, level, serial); level +is a string "a2", "b1", "c1", or '' for a final release. + +New format style '%r' inserts repr(arg) instead of str(arg). + +"in" operator can now be overriden in user-defined classes to mean anything: +it calls the magic method __contains__ + +New calling syntax: f(*args, **kw) equivalent to apply(f, args, kw) + +% ====================================================================== +\section{Extending/embedding Changes} + +Some of the changes are under the covers, and will only be apparent to +people writing C extension modules, or embedding a Python interpreter +in a larger application. If you aren't dealing with Python's C API, +you can safely skip this section since it won't contain anything of +interest to you. + +Users of Jim Fulton's ExtensionClass module will be pleased to find +out that hooks have been added so that ExtensionClasses are now +supported by \function{isinstance()} and \function{issubclass()}. +This means you no longer have to remember to write code such as +\code{if type(obj) == myExtensionClass}, but can use the more natural +\code{if isinstance(obj, myExtensionClass)}. + +The \file{Python/importdl.c} file, which was a mass of #ifdefs to +support dynamic loading on many different platforms, was cleaned up +are reorganized by Greg Stein. \file{importdl.c} is now quite small, +and platform-specific code has been moved into a bunch of +\file{Python/dynload_*.c} files. + +Vladimir Marangozov's long-awaited malloc restructuring was completed, +to make it easy to have the Python interpreter use a custom allocator +instead of C's standard \function{malloc()}. For documentation, read +the comments in \file{Include/mymalloc.h} and +\file{Include/objimpl.h}. For the lengthy discussions during which +the interface was hammered out, see the Web archives of the 'patches' +and 'python-dev' lists at python.org. + +Recent versions of the GUSI % XXX what is GUSI? +development environment for MacOS support POSIX threads. Therefore, +POSIX threads are now supported on the Macintosh too. Threading +support using the user-space GNU pth library was also contributed. + +Threading support on Windows was enhanced, too. Windows supports +thread locks that use kernel objects only in case of contention; in +the common case when there's no contention, they use simpler functions +which are an order of magnitude faster. A threaded version of Python +1.5.2 on NT is twice as slow as an unthreaded version; with the 1.6 +changes, the difference is only 10\%. These improvements were +contributed by Yakov Markovitch. + +% ====================================================================== +\section{Module changes} + +re - changed to be a frontend to sre + +readline, ConfigParser, cgi, calendar, posix, readline, xmllib, aifc, chunk, +wave, random, shelve, nntplib - minor enhancements + +socket, httplib, urllib - optional OpenSSL support + +_tkinter - support for 8.1,8.2,8.3 (support for versions older then 8.0 +has been dropped). Supports Unicode (Lib/lib-tk/Tkinter.py has a test) + +curses -- changed to use ncurses + +% ====================================================================== +\section{New modules} + +winreg - Windows registry interface. +Distutils - tools for distributing Python modules +PyExpat - interface to Expat XML parser +robotparser - parse a robots.txt file (for writing web spiders) +linuxaudio - audio for Linux +mmap - treat a file as a memory buffer +filecmp - supersedes the old cmp.py and dircmp.py modules +tabnanny - check Python sources for tab-width dependance +sre - regular expressions (fast, supports unicode) +unicode - support for unicode +codecs - support for Unicode encoders/decoders + +% ====================================================================== +\section{IDLE Improvements} + +XXX IDLE -- complete overhaul; what are the changes? + +% ====================================================================== +\section{Deleted and Deprecated Modules} + +stdwin + +\end{document} + |