带次数循环

{{{David.D <dengyuanzhong@gmail.com> reply-to python-cn@googlegroups.com, to python-cnCPyUG华蟒用户组 <python-cn@googlegroups.com>, date Sat, Apr 5, 2008 at 11:55 AM }}}subject [CPyUG:45975] [http://groups.google.com/group/python-cn/t/8c9cada1f436b9df python的for如何获得当前循环次数？]

问题

初学者问题：python的for如何获得当前循环次数？ 我现在是这样做的：

i = 0
for item in data:
   ...
   i +=1

有更好的方法吗？

解答

for i in range(len(data)):
  data[i]=xxx

深答

>>> for i,v in enumerate(['a','b']):
...     print i,v
...
0 a
1 b

enumerate

enumerate

• 内建函式!

• e.g

  >>> v_list_ascii=map(lambda x:chr(x),range(ord('a'),ord('z')))
  >>> v_list_ascii
  ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y']
  >>> v_enum=enumerate(v_list_ascii)
  >>> while True:
          try:
                  print v_enum.next()
          except StopIteration:
                  break
  
          
  (0, 'a')
  (1, 'b')
  (2, 'c')
  ......
  (23, 'x')
  (24, 'y')
  
  >>> v_enum=enumerate(v_list_ascii)
  >>> for v_id,v_val in v_enum:
          print v_id,v_val
  
          
  0 a
  1 b
  2 c
  ......
  23 x
  24 y

  example from[http://tinyurl.com/6rv22s a gift from the gods.]

反馈

创建 by -- ZoomQuiet [2008-04-05 04:31:19]