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Diffstat (limited to 'Doc/whatsnew/whatsnew22.tex')
| -rw-r--r-- | Doc/whatsnew/whatsnew22.tex | 138 |
1 files changed, 75 insertions, 63 deletions
diff --git a/Doc/whatsnew/whatsnew22.tex b/Doc/whatsnew/whatsnew22.tex index 1748f14..2b5fb50 100644 --- a/Doc/whatsnew/whatsnew22.tex +++ b/Doc/whatsnew/whatsnew22.tex @@ -82,7 +82,8 @@ create and return a new iterator for the object; if the object is its own iterator, this method can just return \code{self}. In particular, iterators will usually be their own iterators. Extension types implemented in C can implement a \code{tp_iter} function in order to -return an iterator, too. +return an iterator, and extension types that want to behave as +iterators can define a \code{tp_iternext} function. So what do iterators do? They have one required method, \method{next()}, which takes no arguments and returns the next value. @@ -201,19 +202,25 @@ def generate_ints(N): A new keyword, \keyword{yield}, was introduced for generators. Any function containing a \keyword{yield} statement is a generator function; this is detected by Python's bytecode compiler which -compiles the function specially. When you call a generator function, -it doesn't return a single value; instead it returns a generator -object that supports the iterator interface. On executing the -\keyword{yield} statement, the generator outputs the value of -\code{i}, similar to a \keyword{return} statement. The big difference -between \keyword{yield} and a \keyword{return} statement is that, on -reaching a \keyword{yield} the generator's state of execution is -suspended and local variables are preserved. On the next call to the -generator's \code{.next()} method, the function will resume executing -immediately after the \keyword{yield} statement. (For complicated -reasons, the \keyword{yield} statement isn't allowed inside the -\keyword{try} block of a \code{try...finally} statement; read PEP 255 -for a full explanation of the interaction between \keyword{yield} and +compiles the function specially. Because a new keyword was +introduced, generators must be explicitly enabled in a module by +including a \code{from __future__ import generators} statement near +the top of the module's source code. In Python 2.3 this statement +will become unnecessary. + +When you call a generator function, it doesn't return a single value; +instead it returns a generator object that supports the iterator +interface. On executing the \keyword{yield} statement, the generator +outputs the value of \code{i}, similar to a \keyword{return} +statement. The big difference between \keyword{yield} and a +\keyword{return} statement is that, on reaching a \keyword{yield} the +generator's state of execution is suspended and local variables are +preserved. On the next call to the generator's \code{.next()} method, +the function will resume executing immediately after the +\keyword{yield} statement. (For complicated reasons, the +\keyword{yield} statement isn't allowed inside the \keyword{try} block +of a \code{try...finally} statement; read PEP 255 for a full +explanation of the interaction between \keyword{yield} and exceptions.) Here's a sample usage of the \function{generate_ints} generator: @@ -240,16 +247,16 @@ You could equally write \code{for i in generate_ints(5)}, or \code{a,b,c = generate_ints(3)}. Inside a generator function, the \keyword{return} statement can only -be used without a value, and is equivalent to raising the -\exception{StopIteration} exception; afterwards the generator cannot -return any further values. \keyword{return} with a value, such as -\code{return 5}, is a syntax error inside a generator function. You -can also raise \exception{StopIteration} manually, or just let the -thread of execution fall off the bottom of the function, to achieve -the same effect. +be used without a value, and signals the end of the procession of +values; afterwards the generator cannot return any further values. +\keyword{return} with a value, such as \code{return 5}, is a syntax +error inside a generator function. The end of the generator's results +can also be indicated by raising \exception{StopIteration} manually, +or by just letting the flow of execution fall off the bottom of the +function. You could achieve the effect of generators manually by writing your -own class, and storing all the local variables of the generator as +own class and storing all the local variables of the generator as instance variables. For example, returning a list of integers could be done by setting \code{self.count} to 0, and having the \method{next()} method increment \code{self.count} and return it. @@ -308,9 +315,9 @@ structure. \begin{seealso} -\seepep{255}{Simple Generators}{Written by Neil Schemenauer, -Tim Peters, Magnus Lie Hetland. Implemented mostly by Neil -Schemenauer, with fixes from the Python Labs crew.} +\seepep{255}{Simple Generators}{Written by Neil Schemenauer, Tim +Peters, Magnus Lie Hetland. Implemented mostly by Neil Schemenauer +and Tim Peters, with other fixes from the Python Labs crew.} \end{seealso} @@ -516,19 +523,23 @@ See \url{http://www.xmlrpc.com} for more information about XML-RPC. (Contributed by Guido van Rossum, using Ka-Ping Yee's \module{pydoc} module.) \item Various bugfixes and performance improvements have been made -to the SRE engine underlying the \module{re} module. For example, -\function{re.sub()} will now use \function{string.replace()} -automatically when the pattern and its replacement are both just -literal strings without regex metacharacters. Another contributed -patch speeds up certain Unicode character ranges by a factor of -two. (SRE is maintained by Fredrik Lundh. The BIGCHARSET patch -was contributed by Martin von L\"owis.) + to the SRE engine underlying the \module{re} module. For example, + \function{re.sub()} will now use \function{string.replace()} + automatically when the pattern and its replacement are both just + literal strings without regex metacharacters. Another contributed + patch speeds up certain Unicode character ranges by a factor of + two. (SRE is maintained by Fredrik Lundh. The BIGCHARSET patch was + contributed by Martin von L\"owis.) \item The \module{imaplib} module now has support for the IMAP -NAMESPACE extension defined in \rfc{2342}. (Contributed by Michel -Pelletier.) - + NAMESPACE extension defined in \rfc{2342}. (Contributed by Michel + Pelletier.) + \item The \module{rfc822} module's parsing of e-mail addresses is + now compliant with \rfc{2822}, an update to \rfc{822}. The module's + name is \emph{not} going to be changed to \samp{rfc2822}. + (Contributed by Barry Warsaw.) + \end{itemize} @@ -556,33 +567,34 @@ changes are: again. The license changes were also applied to the Python 2.0.1 and 2.1.1 releases. -\item Profiling and tracing functions can now be implemented in C, -which can operate at much higher speeds than Python-based functions -and should reduce the overhead of enabling profiling and tracing, so -it will be of interest to authors of development environments for -Python. Two new C functions were added to Python's API, -\cfunction{PyEval_SetProfile()} and \cfunction{PyEval_SetTrace()}. -The existing \function{sys.setprofile()} and \function{sys.settrace()} -functions still exist, and have simply been changed to use the new -C-level interface. - + \item Profiling and tracing functions can now be implemented in C, + which can operate at much higher speeds than Python-based functions + and should reduce the overhead of enabling profiling and tracing, so + it will be of interest to authors of development environments for + Python. Two new C functions were added to Python's API, + \cfunction{PyEval_SetProfile()} and \cfunction{PyEval_SetTrace()}. + The existing \function{sys.setprofile()} and + \function{sys.settrace()} functions still exist, and have simply + been changed to use the new C-level interface. \item The \file{Tools/scripts/ftpmirror.py} script now parses a \file{.netrc} file, if you have one. - (Contributed by XXX.) Patch \#430754: Makes ftpmirror.py .netrc aware - -\item Some features of the object returned by the \function{xrange()} -function are now deprecated, and trigger warnings when they're -accessed; they'll disappear in Python 2.3. \class{xrange} objects -tried to pretend they were full sequence types by supporting slicing, -sequence multiplication, and the \keyword{in} operator, but these -features were rarely used and therefore buggy. (The implementation of -the \keyword{in} operator had an off-by-one error introduced in Python -XXX that no one noticed until XXX, XXX years later. The -\method{tolist()} method and the \member{start}, \member{stop}, and -\member{step} attributes are also being deprecated. At the C level, -the fourth argument to the \cfunction{PyRange_New()} function, -\samp{repeat}, has also been deprecated. + (Contributed by Mike Romberg.) + + \item Some features of the object returned by the + \function{xrange()} function are now deprecated, and trigger + warnings when they're accessed; they'll disappear in Python 2.3. + \class{xrange} objects tried to pretend they were full sequence + types by supporting slicing, sequence multiplication, and the + \keyword{in} operator, but these features were rarely used and + therefore buggy. The \method{tolist()} method and the + \member{start}, \member{stop}, and \member{step} attributes are also + being deprecated. At the C level, the fourth argument to the + \cfunction{PyRange_New()} function, \samp{repeat}, has also been + deprecated. + + \item On Windows, Python can now be compiled with Borland C thanks + to a number of patches contribued by Stephen Hansen. \item XXX C API: Reorganization of object calling @@ -604,9 +616,9 @@ the tp_call slot, or raise an exception if that's NULL. %PyEval_GetFuncDesc(), PyEval_EvalCodeEx() (formerly get_func_name(), %get_func_desc(), and eval_code2(). - \item XXX SF patch \#418147 Fixes to allow compiling w/ Borland, from Stephen Hansen. - - \item XXX Add support for Windows using "mbcs" as the default Unicode encoding when dealing with the file system. As discussed on python-dev and in patch 410465. + \item XXX Add support for Windows using "mbcs" as the default + Unicode encoding when dealing with the file system. As discussed on + python-dev and in patch 410465. \item XXX Lots of patches to dictionaries; measure performance improvement, if any. @@ -618,6 +630,6 @@ the tp_call slot, or raise an exception if that's NULL. \section{Acknowledgements} The author would like to thank the following people for offering -suggestions on various drafts of this article: No one yet. +suggestions on various drafts of this article: Tim Peters, Neil Schemenauer. \end{document} |