Python itertools模块详解

这货很强大, 必须掌握

文档 链接 http://docs.python.org/2/library/itertools.html

pymotw 链接 http://pymotw.com/2/itertools/

基本是基于文档的翻译和补充，相当于翻译了

itertools用于高效循环的迭代函数集合

组成

总体，整体了解

无限迭代器
代码如下:
迭代器         参数         结果                                                例子
count()     start, [step]   start, start+step, start+2*step, ...                count(10) --> 10 11 12 13 14 ...
cycle()     p               p0, p1, ... plast, p0, p1, ...                      cycle('ABCD') --> A B C D A B C D ...
repeat()    elem [,n]       elem, elem, elem, ... endlessly or up to n times    repeat(10, 3) --> 10 10 10

处理输入序列迭代器
代码如下:
迭代器          参数            结果                                        例子
chain()     p, q, ...           p0, p1, ... plast, q0, q1, ...              chain('ABC', 'DEF') --> A B C D E F
compress()  data, selectors     (d[0] if s[0]), (d[1] if s[1]), ...         compress('ABCDEF', [1,0,1,0,1,1]) --> A C E F
dropwhile() pred, seq           seq[n], seq[n+1], starting when pred fails  dropwhile(lambda x: x<5, [1,4,6,4,1]) --> 6 4 1
groupby()   iterable[, keyfunc] sub-iterators grouped by value of keyfunc(v)
ifilter()   pred, seq           elements of seq where pred(elem) is True    ifilter(lambda x: x%2, range(10)) --> 1 3 5 7 9
ifilterfalse()  pred, seq       elements of seq where pred(elem) is False   ifilterfalse(lambda x: x%2, range(10)) --> 0 2 4 6 8