1.对序列进行分组的函数（摘自web.py源码utils.py文件中）
 1 def group(seq, size): 
 2     """
 3     Returns an iterator over a series of lists of length size from iterable.
 4 
 5         >>> list(group([1,2,3,4], 2))
 6         [[1, 2], [3, 4]]
 7         >>> list(group([1,2,3,4,5], 2))
 8         [[1, 2], [3, 4], [5]]
 9     """
10     def take(seq, n):
11         for i in xrange(n):
12             yield seq.next()
13 
14     if not hasattr(seq, ‘next‘):  
15         seq = iter(seq)
16     
17     while True: 
18         
19         inger=take(seq, size)
20         x = list(inger)
21         if x:
22             yield x
23         else:
24             break