字典的定义
a = {1:2}
1—>key 2—>value 键值是唯一的,值可以是任意数据结构,无序的哈希,json串
字典的访问(查询)
a.get(1)
2
a[1]
2
总结:a.get(key); a[key]
增删改
a = {1:2,3:4,5:6}
a
{1: 2, 3: 4, 5: 6}
a.setdefault(7,8) #增加
8
a
{1: 2, 3: 4, 5: 6, 7: 8}
a.update({3:8}) #修改
a
{1: 2, 3: 8, 5: 6, 7: 8}
a.pop(7) #删除
8
a
{1: 2, 3: 8, 5: 6}
del a #删除
a
Traceback (most recent call last):
Python Shell, prompt 141, line 1
NameError: name 'a' is not defined
字典的遍历
a = {1:2,3:4,5:6}
a.keys()
[1, 3, 5]
a.values()
[2, 4, 6]
a.items()
[(1, 2), (3, 4), (5, 6)]
a = {1:2,3:4,5:6,7:8} #遍历键值
for item in a:
print item
输出:
1
3
5
7
a = {1:2,3:4,5:6,7:8} #遍历值
#for item in a:
#print item
for item in a.values():
print item
输出:
2
4
6
8
a = {1:2,3:4,5:6,7:8} #遍历键值和值
#for item in a:
#print item
#for item in a.values():
#print item
for k,v in a.items():
print k,v
输出:
1 2
3 4
5 6
7 8
核心思想:对字典的操作是讲字典作为序列进行操作,是对字典key的操作