1 >>> dic = {"k1":"v1", "k2":"v2", "k3":"v3", "k4":"v4"}
 2 #循环字典的值
 3 >>> for item in dic.values():
 4     print(item)
 5 v1
 6 v2
 7 v3
 8 v4
 9 
10 #循环字典的键
11 >>> for item in dic.keys():
12     print(item)
13 k1
14 k2
15 k3
16 k4
17 
18 #同时循环字典的键值对
19 >>> for k, v in dic.items():
20     print(k, v)
21 k1 v1
22 k2 v2
23 k3 v3
24 k4 v4

 1 >>> dic = {"k1":"v1", "k2":"v2", "k3":"v3", "k4":"v4"}
 2 #get()方法获取字典的值，若键不存在则返回默认值None，也可以指定默认值
 3 >>> v = dic.get("k1")
 4 >>> v
 5 'v1'
 6 >>> v = dic.get("l")
 7 >>> print(v)
 8 None
 9 >>>v = dic.get("l", 111)
10 >>> v
11 111
12 #pop()方法删除键值对，并返回value，没有该键值对则返回默认值
13 >>> v = dic.pop("f", 1)
14 >>> v
15 1
16 >>> v = dic.pop("k1")
17 >>> v
18 'v1'
19 >>> dic
20 {'k2': 'v2', 'k3': 'v3', 'k4': 'v4'}
21 #popitem()方法最忌删除一个键值对，并返回
22 >>> v = dic.popitem()
23 >>> v
24 ('k4', 'v4')
25 >>> dic
26 {'k1': 'v1', 'k2': 'v2', 'k3': 'v3'}
27 >>> k, v = dic.popitem()
28 >>> print(k, v)
29 k3 v3
30 >>> dic
31 {'k1': 'v1', 'k2': 'v2'}
32 #设置值，若已经存在，不设置，获取当前key对应的值
33 #若不存在，设置，获取当前key对应的值
34 >>> dic = {"k1":"v1", "k2":"v2", "k3":"v3", "k4":"v4"}
35 >>> v = dic.setdefault("k3", "dd")
36 >>> v
37 'v3'
38 >>> v = dic.setdefault("k5", "v5")
39 >>> v
40 'v5'
41 >>> dic
42 {'k1': 'v1', 'k2': 'v2', 'k3': 'v3', 'k4': 'v4', 'k5': 'v5'}
43 
44 #更新字典
45 >>> dic.update({"k1":11})
46 >>> dic
47 {'k1': 11, 'k2': 'v2', 'k3': 'v3', 'k4': 'v4', 'k5': 'v5'}
48 >>> dic.update(k2=22)
49 >>> dic
50 {'k1': 11, 'k2': 22, 'k3': 'v3', 'k4': 'v4', 'k5': 'v5'}