From ad809556baf82755b2cfb0fcae637257f31ca2b4 Mon Sep 17 00:00:00 2001 From: "Andrew M. Kuchling" Date: Sat, 6 Dec 2003 23:19:23 +0000 Subject: Add groupby() --- Doc/whatsnew/whatsnew24.tex | 28 ++++++++++++++++++++++++++++ 1 file changed, 28 insertions(+) diff --git a/Doc/whatsnew/whatsnew24.tex b/Doc/whatsnew/whatsnew24.tex index a52bda9..05b06b5 100644 --- a/Doc/whatsnew/whatsnew24.tex +++ b/Doc/whatsnew/whatsnew24.tex @@ -266,6 +266,34 @@ details. \item The \module{imaplib} module now supports IMAP's THREAD command. (Contributed by Yves Dionne.) +\item The \module{itertools} module gained a + \function{groupby(\var{iterable}\optional{, \var{func}})} function, + inspired by the GROUP BY clause from SQL. + \var{iterable} returns a succession of elements, and the optional + \var{func} is a function that takes an element and returns a key + value; if omitted, the key is simply the element itself. + \function{groupby()} then groups the elements into subsequences + which have matching values of the key, and returns a series of 2-tuples + containing the key value and an iterator over the subsequence. + +Here's an example. The \var{key} function simply returns whether a +number is even or odd, so the result of \function{groupby()} is to +return consecutive runs of odd or even numbers. + +\begin{verbatim} +>>> import itertools +>>> L = [2,4,6, 7,8,9,11, 12, 14] +>>> for key_val, it in itertools.groupby(L, lambda x: x % 2): +... print key_val, list(it) +... +0 [2, 4, 6] +1 [7] +0 [8] +1 [9, 11] +0 [12, 14] +>>> +\end{verbatim} + \item A new \function{getsid()} function was added to the \module{posix} module that underlies the \module{os} module. (Contributed by J. Raynor.) -- cgit v0.12