Update of /cvsroot/python/python/dist/src/Doc/whatsnew In directory sc8-pr-cvs1:/tmp/cvs-serv14684 Modified Files: whatsnew24.tex Log Message: Various fixups: * Add comment on the future of the sets module. * Change a variable from "input" to "data" to avoid shadowing a builtin. * Added possible applications for str.rsplit() and itertools.tee(). * Repaired the example for sorted(). * Cleaned-up the example for operator.itemgetter(). Index: whatsnew24.tex =================================================================== RCS file: /cvsroot/python/python/dist/src/Doc/whatsnew/whatsnew24.tex,v retrieving revision 1.21 retrieving revision 1.22 diff -C2 -d -r1.21 -r1.22 *** whatsnew24.tex 18 Dec 2003 13:28:13 -0000 1.21 --- whatsnew24.tex 31 Dec 2003 01:59:18 -0000 1.22 *************** *** 71,74 **** --- 71,78 ---- % XXX what happens to the sets module? + % The current thinking is that the sets module will be left alone. + % That way, existing code will continue to run without alteration. + % Also, the module provides an autoconversion feature not supported by set() + % and frozenset(). \begin{seealso} *************** *** 106,111 **** \begin{verbatim} ! >>> input = open('/etc/passwd', 'r') ! >>> for line in reversed(list(input)): ... print line ... --- 110,115 ---- \begin{verbatim} ! >>> data = open('/etc/passwd', 'r') ! >>> for line in reversed(list(data)): ... print line ... *************** *** 133,137 **** \item Strings also gained an \method{rsplit()} method that ! works like the \method{split()} method but splits from the end of the string. \begin{verbatim} --- 137,143 ---- \item Strings also gained an \method{rsplit()} method that ! works like the \method{split()} method but splits from the end of ! the string. Possible applications include splitting a filename ! from a path or a domain name from URL. \begin{verbatim} *************** *** 170,174 **** The last example, which uses the \var{cmp} parameter, is the old way ! to perform a case-insensitive sort. It works, but is slower than using a \var{key} parameter. Using \var{key} results in calling the \method{lower()} method once for each element in the list while using --- 176,180 ---- The last example, which uses the \var{cmp} parameter, is the old way ! to perform a case-insensitive sort. It works but is slower than using a \var{key} parameter. Using \var{key} results in calling the \method{lower()} method once for each element in the list while using *************** *** 231,235 **** \item The \function{zip()} built-in function and \function{itertools.izip()} now return an empty list instead of raising a \exception{TypeError} ! exception if called with no arguments. This makes the functions more suitable for use with variable length argument lists: --- 237,241 ---- \item The \function{zip()} built-in function and \function{itertools.izip()} now return an empty list instead of raising a \exception{TypeError} ! exception if called with no arguments. This makes the function more suitable for use with variable length argument lists: *************** *** 320,337 **** \begin{verbatim}

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word = 'abracadabra' ! >>> letters = sorted(word) # Turn string into sorted list of letters letters ['a', 'a', 'a', 'a', 'a', 'b', 'b', 'c', 'd', 'r', 'r'] ! >>> [k for k, g in groupby(word)] # List unique letters ['a', 'b', 'c', 'd', 'r'] ! >>> [(k, len(list(g))) for k, g in groupby(word)] # Count letter occurences [('a', 5), ('b', 2), ('c', 1), ('d', 1), ('r', 2)] ! >>> [k for k, g in groupby(word) if len(list(g)) > 1] # List duplicate letters ['a', 'b', 'r'] \end{verbatim}

! \item \module{itertools} also gained a function named \function{tee(\var{iterator}, \var{N})} that returns \var{N} independent iterators ! that replicate \var{iterator}. If \var{N} is omitted, the default is ! 2. \begin{verbatim} --- 326,344 ---- \begin{verbatim}

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word = 'abracadabra' ! >>> letters = sorted(word) # Turn string into a sorted list of letters letters ['a', 'a', 'a', 'a', 'a', 'b', 'b', 'c', 'd', 'r', 'r'] ! >>> [k for k, g in groupby(letters)] # List unique letters ['a', 'b', 'c', 'd', 'r'] ! >>> [(k, len(list(g))) for k, g in groupby(letters)] # Count letter occurences [('a', 5), ('b', 2), ('c', 1), ('d', 1), ('r', 2)] ! >>> [k for k, g in groupby(letters) if len(list(g)) > 1] # List duplicated letters ['a', 'b', 'r'] \end{verbatim}

! \item \module{itertools} also gained a function named ! \function{tee(\var{iterator}, \var{N})} that returns \var{N} independent ! iterators that replicate \var{iterator}. If \var{N} is omitted, the ! default is 2. \begin{verbatim} *************** *** 340,353 ****

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i1,i2 (<itertools.tee object at 0x402c2080>, <itertools.tee object at 0x402c2090>) ! >>> list(i1) [1, 2, 3] ! >>> list(i2) [1, 2, 3] \end{verbatim}

Note that \function{tee()} has to keep copies of the values returned ! by the iterator; in the worst case it may need to keep all of them. ! This should therefore be used carefully if \var{iterator} ! returns a very large stream of results. \item A new \function{getsid()} function was added to the --- 347,364 ----

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i1,i2 (<itertools.tee object at 0x402c2080>, <itertools.tee object at 0x402c2090>) ! >>> list(i1) # Run the first iterator to exhaustion [1, 2, 3] ! >>> list(i2) # Run the second iterator to exhaustion [1, 2, 3] \end{verbatim}

Note that \function{tee()} has to keep copies of the values returned ! by the iterator; in the worst case, it may need to keep all of them. ! This should therefore be used carefully if there the leading iterator ! can run far ahead of the trailing iterator in a long stream of inputs. ! If the separation is large, then it becomes preferrable to use ! \function{list()} instead. When the iterators track closely with one ! another, \function{tee()} is ideal. Possible applications include ! bookmarking, windowing, or lookahead iterators. \item A new \function{getsid()} function was added to the *************** *** 358,374 **** \function{attrgetter(\var{attr})} and \function{itemgetter(\var{index})}. Both functions return callables that take a single argument and return ! the corresponding attribute or item; these callables are handy for use ! with \function{map()} or \function{list.sort()}. For example, here's a simple ! us \begin{verbatim} ! >>> L = [('c', 2), ('d', 1), ('a', '4'), ('b', 3)]

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map(operator.itemgetter(0), L) ['c', 'd', 'a', 'b'] map(operator.itemgetter(1), L) ! [2, 1, '4', 3] ! >>> L.sort(key=operator.itemgetter(1)) # Sort list by second item in tuples ! >>> L ! [('d', 1), ('c', 2), ('b', 3), ('a', '4')] \end{verbatim}

--- 369,384 ---- \function{attrgetter(\var{attr})} and \function{itemgetter(\var{index})}. Both functions return callables that take a single argument and return ! the corresponding attribute or item; these callables make excellent ! data extractors when used with \function{map()} or \function{sorted()}. ! For example: \begin{verbatim} ! >>> L = [('c', 2), ('d', 1), ('a', 4), ('b', 3)]

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map(operator.itemgetter(0), L) ['c', 'd', 'a', 'b'] map(operator.itemgetter(1), L) ! [2, 1, 4, 3] ! >>> sorted(L, key=operator.itemgetter(1)) # Sort list by second tuple item ! [('d', 1), ('c', 2), ('b', 3), ('a', 4)] \end{verbatim}

*************** *** 377,381 **** \method{randrange()} method, making it possible to efficiently generate arbitrarily large random numbers (suitable for prime number generation in ! RSA applications). \item The regular expression language accepted by the \module{re} module --- 387,391 ---- \method{randrange()} method, making it possible to efficiently generate arbitrarily large random numbers (suitable for prime number generation in ! RSA applications for example). \item The regular expression language accepted by the \module{re} module