itertools库

In [1]: import itertools

In [2]: dir(itertools)
Out[2]: 
['__doc__',
 '__file__',
 '__name__',
 '__package__',
 'chain',
 'combinations',
 'combinations_with_replacement',
 'compress',
 'count',
 'cycle',
 'dropwhile',
 'groupby',
 'ifilter',
 'ifilterfalse',
 'imap',
 'islice',
 'izip',
 'izip_longest',
 'permutations',
 'product',
 'repeat',
 'starmap',
 'takewhile',
 'tee']

1. itertools.chain

   # 连接多个列表或生成器
   In [7]: list(itertools.chain(range(3), range(3,6), [6,7,8,9]))
   Out[7]: [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

2. itertools.combinations

   # 求列表或生成器中指定数目的元素不重复的所有组合
   In [4]: list(itertools.combinations(range(5), 3))
   Out[4]: 
   [(0, 1, 2),
    (0, 1, 3),
    (0, 1, 4),
    (0, 2, 3),
    (0, 2, 4),
    (0, 3, 4),
    (1, 2, 3),
    (1, 2, 4),
    (1, 3, 4),
    (2, 3, 4)]