python之字典遍历方法

字典遍历分为三种：

1. 遍历key
2. 遍历value
3. 遍历key-value

key遍历：

>>> person={'name':'lizhong','age':'','city':'BeiJing'}
>>> for key in person.keys():
    print(key)
 
name
age
city

value遍历：

>>> for value in person.values():
    print(value)
 
lizhong
26
BeiJing

key-value遍历：

>>> for key, value in person.items():
    print(key, value)
 
name lizhong
age 26
city BeiJing

关于items()

>>> person
{'name': 'lizhong', 'age': '', 'city': 'BeiJing'}
>>> person.items()
dict_items([('name', 'lizhong'), ('age', ''), ('city', 'BeiJing')])

由以上可得：items()以列表(list)的方式返回可遍历的(key, value)元组(tuple)数组