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| -rw-r--r-- | Doc/whatsnew/whatsnew23.tex | 203 |
1 files changed, 192 insertions, 11 deletions
diff --git a/Doc/whatsnew/whatsnew23.tex b/Doc/whatsnew/whatsnew23.tex index 6ff6fb7..effb48a 100644 --- a/Doc/whatsnew/whatsnew23.tex +++ b/Doc/whatsnew/whatsnew23.tex @@ -12,13 +12,11 @@ % MacOS framework-related changes (section of its own, probably) -% the new set-next-statement functionality of pdb (SF #643835) - %\section{Introduction \label{intro}} -{\large This article is a draft, and is currently up to date for some -random version of the CVS tree from early November 2002. Please send any -additions, comments or errata to the author.} +{\large This article is a draft, and is currently up to date for +Python 2.3alpha1. Please send any additions, comments or errata to +the author.} This article explains the new features in Python 2.3. The tentative release date of Python 2.3 is currently scheduled for some undefined @@ -647,6 +645,128 @@ Walter D\"orwald.} %====================================================================== +\section{PEP 273: Importing Modules from Zip Archives} + +The new \module{zipimport} module adds support for importing +modules from a ZIP-format archive. You shouldn't need to import the +module explicitly; it will be automatically imported if a ZIP +archive's filename is added to \code{sys.path}. For example: + +\begin{verbatim} +amk@nyman:~/src/python$ unzip -l /tmp/example.zip +Archive: /tmp/example.zip + Length Date Time Name + -------- ---- ---- ---- + 8467 11-26-02 22:30 jwzthreading.py + -------- ------- + 8467 1 file +amk@nyman:~/src/python$ ./python +Python 2.3a0 (#1, Dec 30 2002, 19:54:32) +[GCC 2.96 20000731 (Red Hat Linux 7.3 2.96-113)] on linux2 +Type "help", "copyright", "credits" or "license" for more information. +>>> import sys +>>> sys.path.insert(0, '/tmp/example.zip') # Add .zip file to front of path +>>> import jwzthreading +>>> jwzthreading.__file__ +'/tmp/example.zip/jwzthreading.py' +>>> +\end{verbatim} + +An entry in \code{sys.path} can now be the filename of a ZIP archive. +The ZIP archive can contain any kind of files, but only files named +\code{*.py}, \code{*.pyc}, or \code{*.pyo} can be imported. If an +archive only contains \code{*.py} files, Python will not attempt to +modify the archive by adding the corresponding {*.pyc} file. +Therefore, if a ZIP archive doesn't contain {*.pyc} files, importing +may be rather slow. + +A path within the archive can also be specified to only import from a +subdirectory; for example, the path \file{/tmp/example.zip/lib/} +would only import from the \file{lib/} subdirectory within the +archive. + +This new feature is implemented using the new import hooks from +\pep{302}; see section~\ref{section-pep302} for a description. + +\begin{seealso} + +\seepep{273}{Import Modules from Zip Archives}{Written by James C. Ahlstrom, +who also provided an implementation. +Python 2.3 follows the specification in \pep{273}, +but uses an implementation written by Just van Rossum +that uses the import hooks described in \pep{302}.} + +\end{seealso} + +%====================================================================== +\section{PEP 302: New Import Hooks \label{section-pep302}} + +While it's been possible to write custom import hooks ever since the +\module{ihooks} module was introduced in Python 1.3, no one has ever +been really happy with it, because writing new import hooks is +difficult and messy. There have been various alternative interfaces +proposed, such as the \module{imputil} and \module{iu} modules, but +none has ever gained much acceptance, and none was easily usable from +\C{} code. + +\pep{302} borrows ideas from its predecessors, especially from +Gordon McMillan's \module{iu} module. Three new items +are added to the \module{sys} module: + +\begin{itemize} + \item[\code{sys.path_hooks}] is a list of functions. Each function +takes a string containing a path and returns either \code{None} or an +importer object that will handle imports from this path. + + \item[\code{sys.path_importer_cache}] caches importer objects for +each path, so \code{sys.path_hooks} will only need to be traversed +once for each path. + + \item[\code{sys.meta_path}] is a list of importer objects +that will be traversed before \code{sys.path} is checked at all. +This list is initially empty, but can be extended. Additional built-in +and frozen modules can be imported by an object added to this list. + +\end{itemize} + +Importer objects must have a single method, +\method{find_module(\var{fullname}, \var{path}=None)}. \var{fullname} +will be a module or package name, e.g. \samp{string} or +\samp{spam.ham}. \method{find_module()} must return a loader object +that has a single method, \method{load_module(\var{fullname})}, that +creates and returns the corresponding module object. + +Pseudo-code for Python's new import logic, therefore, looks something +like this (simplified a bit; see \pep{302} for the full details): + +\begin{verbatim} +for mp in sys.meta_path: + loader = mp(fullname) + if loader is not None: + <module> = loader(fullname) + +for path in sys.path: + for hook in sys.path_hooks: + importer = hook(path) + if importer is not None: + loader = importer.find_module(fullname) + return loader.load_module(fullname) + +# Not found! +raise ImportError +\end{verbatim} + +\begin{seealso} + +\seepep{302}{New Import Hooks}{Written by Just van~Rossum and Paul Moore. +Implemented by Just van Rossum. +% XXX is that credit right? +} + +\end{seealso} + + +%====================================================================== \section{Extended Slices\label{section-slices}} Ever since Python 1.4, the slicing syntax has supported an optional @@ -797,7 +917,8 @@ section~\ref{section-bool} of this document. integer instead of raising an \exception{OverflowError} when a string or floating-point number is too large to fit into an integer. This can lead to the paradoxical result that -\code{isinstance(int(\var{expression}), int)} is false, but that seems unlikely to cause problems in practice. +\code{isinstance(int(\var{expression}), int)} is false, but that seems +unlikely to cause problems in practice. \item Built-in types now support the extended slicing syntax, as described in section~\ref{section-slices} of this document. @@ -835,7 +956,7 @@ creates a dictionary with keys taken from the supplied iterator (Patches contributed by Raymond Hettinger.) -The \function{dict()} constructor now also accepts keyword arguments to +Also, the \function{dict()} constructor now accepts keyword arguments to simplify creating small dictionaries: \begin{verbatim} @@ -1012,6 +1133,9 @@ Oren Tirosh.) \begin{itemize} +\item The creation of new-style class instances has been made much +faster; they're now faster than classic classes! + \item The \method{sort()} method of list objects has been extensively rewritten by Tim Peters, and the implementation is significantly faster. @@ -1056,7 +1180,7 @@ support using the \code{+=} assignment operator to add another array's contents, and the \code{*=} assignment operator to repeat an array. (Contributed by Jason Orendorff.) -\item The \module{bsddb} module has been updated to version 3.4.0 +\item The \module{bsddb} module has been updated to version 4.1.1 of the \ulink{PyBSDDB}{http://pybsddb.sourceforge.net} package, providing a more complete interface to the transactional features of the BerkeleyDB library. @@ -1118,6 +1242,8 @@ now return enhanced tuples: ('amk', 500) \end{verbatim} +\item The \module{gzip} module can now handle files exceeding 2~Gb. + \item The new \module{heapq} module contains an implementation of a heap queue algorithm. A heap is an array-like data structure that keeps items in a partially sorted order such that, @@ -1218,13 +1344,21 @@ ValueError: sample larger than population >>> random.sample(xrange(1,10000,2), 10) # Choose ten odds under 10000 [3407, 3805, 1505, 7023, 2401, 2267, 9733, 3151, 8083, 9195] \end{verbatim} - -(Contributed by Raymond Hettinger.) + +The \module{random} module now uses a new algorithm, the Mersenne +Twister, implemented in C. It's faster and more extensively studied +than the previous algorithm. + +(All changes contributed by Raymond Hettinger.) \item The \module{readline} module also gained a number of new functions: \function{get_history_item()}, \function{get_current_history_length()}, and \function{redisplay()}. +\item The \module{shutil} module gained a \function{move(\var{src}, +\var{dest})} that recursively moves a file or directory to a new +location. + \item Support for more advanced POSIX signal handling was added to the \module{signal} module by adding the \function{sigpending}, \function{sigprocmask} and \function{sigsuspend} functions, where supported @@ -1284,6 +1418,28 @@ documentation for details. %XXX add a link to the module docs? (Contributed by Greg Ward.) +\item The \module{thread} and \module{threading} modules now have +companion, \module{dummy_thread} and \module{dummy_threading}, that +provide a do-nothing implementation of the \module{thread} module's +interface, even if threads are not supported. The intention is to +simplify thread-aware modules (that \emph{don't} rely on threads to +run) by putting the following code at the top: + +% XXX why as _threading? +\begin{verbatim} +try: + import threading as _threading +except ImportError: + import dummy_threading as _threading +\end{verbatim} + +Code can then call functions and use classes in \module{_threading} +whether or not threads are supported, avoiding an \keyword{if} +statement and making the code slightly clearer. This module will not +magically make multithreaded code run without threads; code that waits +for another thread to return or to do something will simply hang +forever. + \item The \module{time} module's \function{strptime()} function has long been an annoyance because it uses the platform C library's \function{strptime()} implementation, and different platforms @@ -1610,6 +1766,8 @@ allocate objects, and \cfunction{PyObject_GC_Del} to deallocate them. \end{itemize} +It's also no longer possible to build Python without the garbage collector. + \item Python can now optionally be built as a shared library (\file{libpython2.3.so}) by supplying \longprogramopt{enable-shared} when running Python's \program{configure} script. (Contributed by Ondrej @@ -1672,6 +1830,22 @@ Expat. \end{itemize} +\begin{comment} +%====================================================================== +\subsection{Date/Time Type} + +Date and time types suitable for expressing timestamps were added as +the \module{datetime} module. The types don't support different +calendars or many fancy features, and just stick to the basics. + +The three primary types are: \class{date}, representing a day, month, +and year; \class{time}, consisting of hour, minute, and second value; +and \class{datetime}, which contains both a date and a time. + +XXX finish this section +\end{comment} + + %====================================================================== \subsection{Port-Specific Changes} @@ -1695,7 +1869,8 @@ The RPM spec files, found in the \file{Misc/RPM/} directory in the Python source distribution, were updated for 2.3. (Contributed by Sean Reifschneider.) -Python now supports AtheOS (\url{http://www.atheos.cx}) and GNU/Hurd. +Python now supports AtheOS (\url{http://www.atheos.cx}), GNU/Hurd, +OpenVMS, and OS/2 with EMX. %====================================================================== @@ -1738,6 +1913,12 @@ should instead call \code{PyCode_Addr2Line(f->f_code, f->f_lasti)}. This will have the added effect of making the code work as desired under ``python -O'' in earlier versions of Python. +A nifty new feature is that trace functions can now the +\member{f_lineno} attribute of frame objects can now be assigned to, +changing the line that will be executed next. A \samp{jump} command +has been added to the \module{pdb} debugger taking advantage of this +new feature. (Implemented by Richie Hindle.) + \end{itemize} |