224 lines
6.8 KiB
TeX
224 lines
6.8 KiB
TeX
\documentclass{howto}
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\usepackage{distutils}
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% $Id$
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\title{What's New in Python 2.5}
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\release{0.0}
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\author{A.M. Kuchling}
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\authoraddress{\email{amk@amk.ca}}
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\begin{document}
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\maketitle
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\tableofcontents
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This article explains the new features in Python 2.5. No release date
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for Python 2.5 has been set; it will probably be released in late 2005.
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% Compare with previous release in 2 - 3 sentences here.
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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 2.5.
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% add hyperlink when the documentation becomes available online.
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If 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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%======================================================================
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\section{PEP 309: Partial Function Application}
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XXX describe this PEP.
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%======================================================================
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\section{Other Language Changes}
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Here are all of the changes that Python 2.5 makes to the core Python
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language.
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\begin{itemize}
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\item The \function{min()} and \function{max()} built-in functions
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gained a \code{key} keyword argument analogous to the \code{key}
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argument for \method{sort()}. This argument supplies a function
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that takes a single argument and is called for every value in the list;
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\function{min()}/\function{max()} will return the element with the
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smallest/largest return value from this function.
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For example, to find the longest string in a list, you can do:
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\begin{verbatim}
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L = ['medium', 'longest', 'short']
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# Prints 'longest'
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print max(L, key=len)
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# Prints 'short', because lexicographically 'short' has the largest value
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print max(L)
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\end{verbatim}
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(Contributed by Steven Bethard and Raymond Hettinger.)
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\item The list of base classes in a class definition can now be empty.
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As an example, this is now legal:
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\begin{verbatim}
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class C():
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pass
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\end{verbatim}
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(Implemented by Brett Cannon.)
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\end{itemize}
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%======================================================================
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\subsection{Optimizations}
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\begin{itemize}
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\item Optimizations should be described here.
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\end{itemize}
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The net result of the 2.5 optimizations is that Python 2.5 runs the
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pystone benchmark around XX\% faster than Python 2.4.
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%======================================================================
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\section{New, Improved, and Deprecated Modules}
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As usual, Python's standard library received a number of enhancements and
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bug fixes. Here's a partial list of the most notable changes, sorted
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alphabetically by module name. Consult the
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\file{Misc/NEWS} file in the source tree for a more
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complete list of changes, or look through the CVS logs for all the
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details.
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\begin{itemize}
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% the cPickle module no longer accepts the deprecated None option in the
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% args tuple returned by __reduce__().
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% csv module improvements
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% datetime.datetime() now has a strptime class method which can be used to
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% create datetime object using a string and format.
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\item The \function{nsmallest()} and
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\function{nlargest()} functions in the \module{heapq} module
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now support a \code{key} keyword argument similar to the one
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provided by the \function{min()}/\function{max()} functions
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and the \method{sort()} methods. For example:
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Example:
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\begin{verbatim}
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>>> import heapq
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>>> L = ["short", 'medium', 'longest', 'longer still']
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>>> heapq.nsmallest(2, L) # Return two lowest elements, lexicographically
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['longer still', 'longest']
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>>> heapq.nsmallest(2, L, key=len) # Return two shortest elements
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['short', 'medium']
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\end{verbatim}
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(Contributed by Raymond Hettinger.)
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\item The \function{itertools.islice()} function now accepts
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\code{None} for the start and step arguments. This makes it more
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compatible with the attributes of slice objects, so that you can now write
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the following:
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\begin{verbatim}
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s = slice(5) # Create slice object
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itertools.islice(iterable, s.start, s.stop, s.step)
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\end{verbatim}
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(Contributed by Raymond Hettinger.)
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\item New module: \module{spwd} provides functions for accessing the
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shadow password database on systems that support it.
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% XXX give example
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\item The \module{os} module underwent a number of changes. The
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\member{stat_float_times} variable now defaults to true, meaning that
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\function{os.stat()} will now return time values as floats. (This
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doesn't necessarily mean that \function{os.stat()} will return times
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that are precise to fractions of a second; not all systems support
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such precision.)
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Also, constants named \member{os.SEEK_SET}, \member{os.SEEK_CUR}, and
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\member{os.SEEK_END} have been added; these are the parameters to the
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\function{os.lseek()} function.
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\item The \class{TarFile} class in the \module{tarfile} module now has
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a \method{extractall()} method that extracts all members from the
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archive into the current working directory. It's also possible to set
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a different directory as the extraction target, and to unpack only a
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subset of the archive's members. (Contributed by Lars Gust\"abel.)
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%======================================================================
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% whole new modules get described in \subsections here
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% ======================================================================
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\section{Build and C API Changes}
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Changes to Python's build process and to the C API include:
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\begin{itemize}
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\item The \cfunction{PyRange_New()} function was removed. It was never documented,
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never used in the core code, and had dangerously lax error checking.
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\end{itemize}
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%======================================================================
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\subsection{Port-Specific Changes}
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Platform-specific changes go here.
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%======================================================================
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\section{Other Changes and Fixes \label{section-other}}
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As usual, there were a bunch of other improvements and bugfixes
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scattered throughout the source tree. A search through the CVS change
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logs finds there were XXX patches applied and YYY bugs fixed between
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Python 2.4 and 2.5. Both figures are likely to be underestimates.
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Some of the more notable changes are:
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\begin{itemize}
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\item Details go here.
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\end{itemize}
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%======================================================================
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\section{Porting to Python 2.5}
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This section lists previously described changes that may require
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changes to your code:
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\begin{itemize}
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\item Some old deprecated modules (\module{statcache}, \module{tzparse},
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\module{whrandom}) have been moved to \file{Lib/lib-old}.
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% XXX note how to get them back
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% the pickle module no longer uses the deprecated bin parameter.
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\end{itemize}
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%======================================================================
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\section{Acknowledgements \label{acks}}
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The author would like to thank the following people for offering
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suggestions, corrections and assistance with various drafts of this
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article: .
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\end{document}
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