| \documentclass{howto} |
| \usepackage{distutils} |
| % $Id$ |
| |
| |
| \title{What's New in Python 2.5} |
| \release{0.0} |
| \author{A.M. Kuchling} |
| \authoraddress{\email{amk@amk.ca}} |
| |
| \begin{document} |
| \maketitle |
| \tableofcontents |
| |
| This article explains the new features in Python 2.5. No release date |
| for Python 2.5 has been set; it will probably be released in late 2005. |
| |
| % Compare with previous release in 2 - 3 sentences here. |
| |
| This article doesn't attempt to provide a complete specification of |
| the new features, but instead provides a convenient overview. For |
| full details, you should refer to the documentation for Python 2.5. |
| % add hyperlink when the documentation becomes available online. |
| If you want to understand the complete implementation and design |
| rationale, refer to the PEP for a particular new feature. |
| |
| |
| %====================================================================== |
| \section{PEP 309: Partial Function Application} |
| |
| For programs written in a functional style, it can be useful to |
| construct variants of existing functions that have some of the |
| parameters filled in. This is called ``partial function application''. |
| The new \module{functional} module contains a \class{partial} class |
| that provides partial application. |
| |
| The \module{functional} module is intended to contain tools for |
| functional-style programming. Currently it only contains |
| \class{partial}, but new functions will probably be added in future |
| versions of Python. |
| |
| % XXX write rest of this |
| % XXX add example from my GTk programming |
| |
| |
| \begin{seealso} |
| |
| \seepep{309}{Partial Function Application}{PEP proposed and written by |
| Peter Harris; implemented by Hye-Shik Chang, with adaptations by |
| Raymond Hettinger.} |
| |
| \end{seealso} |
| |
| |
| %====================================================================== |
| \section{PEP 314: Metadata for Python Software Packages v1.1} |
| |
| XXX describe this PEP. |
| distutils \function{setup()} now supports the \var{provides}, |
| \var{requires}, \var{obsoletes} keywords. |
| |
| |
| %====================================================================== |
| \section{Other Language Changes} |
| |
| Here are all of the changes that Python 2.5 makes to the core Python |
| language. |
| |
| \begin{itemize} |
| |
| \item The \function{min()} and \function{max()} built-in functions |
| gained a \code{key} keyword argument analogous to the \code{key} |
| argument for \method{sort()}. This argument supplies a function |
| that takes a single argument and is called for every value in the list; |
| \function{min()}/\function{max()} will return the element with the |
| smallest/largest return value from this function. |
| For example, to find the longest string in a list, you can do: |
| |
| \begin{verbatim} |
| L = ['medium', 'longest', 'short'] |
| # Prints 'longest' |
| print max(L, key=len) |
| # Prints 'short', because lexicographically 'short' has the largest value |
| print max(L) |
| \end{verbatim} |
| |
| (Contributed by Steven Bethard and Raymond Hettinger.) |
| |
| \item The list of base classes in a class definition can now be empty. |
| As an example, this is now legal: |
| |
| \begin{verbatim} |
| class C(): |
| pass |
| \end{verbatim} |
| (Implemented by Brett Cannon.) |
| |
| \end{itemize} |
| |
| |
| %====================================================================== |
| \subsection{Optimizations} |
| |
| \begin{itemize} |
| |
| \item Optimizations should be described here. |
| |
| \end{itemize} |
| |
| The net result of the 2.5 optimizations is that Python 2.5 runs the |
| pystone benchmark around XX\% faster than Python 2.4. |
| |
| |
| %====================================================================== |
| \section{New, Improved, and Deprecated Modules} |
| |
| 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 CVS logs for all the |
| details. |
| |
| \begin{itemize} |
| |
| % the cPickle module no longer accepts the deprecated None option in the |
| % args tuple returned by __reduce__(). |
| |
| % csv module improvements |
| |
| % datetime.datetime() now has a strptime class method which can be used to |
| % create datetime object using a string and format. |
| |
| \item The \function{nsmallest()} and |
| \function{nlargest()} functions in the \module{heapq} module |
| now support a \code{key} keyword argument similar to the one |
| provided by the \function{min()}/\function{max()} functions |
| and the \method{sort()} methods. For example: |
| Example: |
| |
| \begin{verbatim} |
| >>> import heapq |
| >>> L = ["short", 'medium', 'longest', 'longer still'] |
| >>> heapq.nsmallest(2, L) # Return two lowest elements, lexicographically |
| ['longer still', 'longest'] |
| >>> heapq.nsmallest(2, L, key=len) # Return two shortest elements |
| ['short', 'medium'] |
| \end{verbatim} |
| |
| (Contributed by Raymond Hettinger.) |
| |
| \item The \function{itertools.islice()} function now accepts |
| \code{None} for the start and step arguments. This makes it more |
| compatible with the attributes of slice objects, so that you can now write |
| the following: |
| |
| \begin{verbatim} |
| s = slice(5) # Create slice object |
| itertools.islice(iterable, s.start, s.stop, s.step) |
| \end{verbatim} |
| |
| (Contributed by Raymond Hettinger.) |
| |
| \item New module: \module{spwd} provides functions for accessing the |
| shadow password database on systems that support it. |
| % XXX give example |
| |
| \item The \module{os} module underwent a number of changes. The |
| \member{stat_float_times} variable now defaults to true, meaning that |
| \function{os.stat()} will now return time values as floats. (This |
| doesn't necessarily mean that \function{os.stat()} will return times |
| that are precise to fractions of a second; not all systems support |
| such precision.) |
| |
| Also, constants named \member{os.SEEK_SET}, \member{os.SEEK_CUR}, and |
| \member{os.SEEK_END} have been added; these are the parameters to the |
| \function{os.lseek()} function. |
| |
| \item The \class{TarFile} class in the \module{tarfile} module now has |
| a \method{extractall()} method that extracts all members from the |
| archive into the current working directory. It's also possible to set |
| a different directory as the extraction target, and to unpack only a |
| subset of the archive's members. (Contributed by Lars Gust\"abel.) |
| |
| |
| |
| |
| %====================================================================== |
| % whole new modules get described in \subsections here |
| |
| |
| % ====================================================================== |
| \section{Build and C API Changes} |
| |
| Changes to Python's build process and to the C API include: |
| |
| \begin{itemize} |
| |
| \item The \cfunction{PyRange_New()} function was removed. It was never documented, |
| never used in the core code, and had dangerously lax error checking. |
| |
| \end{itemize} |
| |
| |
| %====================================================================== |
| \subsection{Port-Specific Changes} |
| |
| Platform-specific changes go here. |
| |
| |
| %====================================================================== |
| \section{Other Changes and Fixes \label{section-other}} |
| |
| As usual, there were a bunch of other improvements and bugfixes |
| scattered throughout the source tree. A search through the CVS change |
| logs finds there were XXX patches applied and YYY bugs fixed between |
| Python 2.4 and 2.5. Both figures are likely to be underestimates. |
| |
| Some of the more notable changes are: |
| |
| \begin{itemize} |
| |
| \item Details go here. |
| |
| \end{itemize} |
| |
| |
| %====================================================================== |
| \section{Porting to Python 2.5} |
| |
| This section lists previously described changes that may require |
| changes to your code: |
| |
| \begin{itemize} |
| |
| \item Some old deprecated modules (\module{statcache}, \module{tzparse}, |
| \module{whrandom}) have been moved to \file{Lib/lib-old}. |
| You can get access to these modules again by adding the directory |
| to your \code{sys.path}: |
| |
| \begin{verbatim} |
| import os |
| from distutils import sysconfig |
| |
| lib_dir = sysconfig.get_python_lib(standard_lib=True) |
| old_dir = os.path.join(lib_dir, 'lib-old') |
| sys.path.append(old_dir) |
| \end{verbatim} |
| |
| Doing so is discouraged, however; it's better to update any code that |
| still uses these modules. |
| |
| % the pickle module no longer uses the deprecated bin parameter. |
| |
| \end{itemize} |
| |
| |
| %====================================================================== |
| \section{Acknowledgements \label{acks}} |
| |
| The author would like to thank the following people for offering |
| suggestions, corrections and assistance with various drafts of this |
| article: . |
| |
| \end{document} |