收藏一些python的小技能
例子1：For .. else 语法
foo=[2,1]
for i in foo:
if i == 0:
break
else: print("i was never 0")
例子2：for in 输出索引
>>> a = ['a', 'b', 'c', 'd', 'e']
>>> for index, item in enumerate(a): print index, item
...
0 a
1 b
2 c
3 d
4 e
>>>
例子3：string 分割函数
cars = ['Red_sedan', 'Big_truck', 'Small_roadster']
for car in cars:
head, sep, tail = car.partition('_')
print tail
>>>Red _ sedan
>>>Big _ truck
>>>Small _ roadster
例子4： python键值对转换
>>> a_dict = {'a': 1, 'b': 2, 'c': 3}
>>> {value:key for key, value in a_dict.items()}
{1: 'a', 2: 'b', 3: 'c'}
