Python enumerate

enumerate() 函数用于将一个可遍历的数据对象(如列表、元组或字符串)组合为一个索引序列，同时列出数据和数据下标，一般用在 for 循环当中。

普通的 for 循环
>>> i = 0
>>> seq = ['one', 'two', 'three']
>>> for element in seq:
...     print i, seq[i]
...     i += 1
...
0 one
1 two
2 three

for 循环使用 enumerate
>>> seq = ['one', 'two', 'three']
>>> for i, element in enumerate(seq):
...     print i, element
...
0 one
1 two
2 three