python三大内建数据结构之字典（dict）

字典（dict）：一组无序的组合数据，以键值对形式出现。

创建

# 1
dict1 = {}
# 2
dict1 = {"one": 1, "two": 2, "three": 3}

访问

dict1 = {"one": 1, "two": 2, "three": 3}
print(dict1["one"])
dict1["one"] = 4
print(dict1["one"])

成员检测只检测key。其他类似于list。

 遍历

dict1 = {"one": 1, "two": 2, "three": 3}
for k in dict1:
    print(k, dict1[k])
for k in dict1.keys():
    print(k, dict1[k])
for v in dict1.values():
    print(v)
for k, v in dict1.items():
    print(k, v)

字典生存方式

dict1 = {"one": 1, "two": 2, "three": 3}
dict2 = {k: v for k, v in dict1.items() if v % 2 == 0}
print(dict2)

 

clear等同list。

get用法

dict1 = {"one": 1, "two": 2, "three": 3}
print(dict1.get("one"))
print(dict1.get("four",4))