使用enumerate( )方法的好处：可以同时拿到index和value。示例代码如下：
# coding:utf-8
trs = ["China", "America", "Korea", "England"]
for tr in trs:
print tr
print "*"*30
# 使用enumerate()方法
for index, tr in enumerate(trs):
print "{}: ".format(index)+tr
print trs[0]
输出结果为：
D:\Python2.7\python.exe D:/PyCharm/dytt_spider/text.py China America Korea England ****************************** 0: China 1: America 2: Korea 3: England China Process finished with exit code 0