python字典相关
无序、键不重复 且 元素只能是键值对的可变的 个 容器。
dict = {} #空字典
-
键:必须可哈希。 目前为止学到的可哈希的类型:int/bool/str/tuple;不可哈希的类型:list/set/dict。(集合)
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值:任意类型。
1. 获取值
info = {
"age":12,
"status":True,
"name":"武沛齐",
"data":None
}
data1 = info.get("name")
2. 所有的键
info = {"age":12, "status":True, "name":"wupeiqi","email":"xx@live.com"}
data = info.keys()
3.所有的值
info = {"age":12, "status":True, "name":"wupeiqi","email":"xx@live.com"}
data = info.values()
4. 所有的键值
info = {"age":12, "status":True, "name":"wupeiqi","email":"xx@live.com"}
data = info.items()
5. 设置值
data = {
"name": "武沛齐",
"email": 'xxx@live.com'
}
data.setdefault("age", 18)
6. 更新字典键值对
info = {"age":12, "status":True}
info.update( {"age":14,"name":"武沛齐"} ) # info中没有的键直接添加;有的键则更新值
7. 移除指定键值对
info = {"age":12, "status":True,"name":"武沛齐"}
data = info.pop("age")
print(info) # {"status":True,"name":"武沛齐"}
print(data) # 12
8. 按照顺序移除(后进先出)
info = {"age":12, "status":True,"name":"武沛齐"}
data = info.popitem() # ("name","武沛齐" )
print(info) # {"age":12, "status":True}
print(data) # ("name","武沛齐")
9. 求并集
(Python3.9新加入)
v1 = {"k1": 1, "k2": 2}
v2 = {"k2": 22, "k3": 33}
v3 = v1 | v2
print(v3) # {'k1': 1, 'k2': 22, 'k3': 33}
10. 长度
info = {"age":12, "status":True,"name":"武沛齐"}
data = len(info)
11. in
12. 索引(键)字典不同于元组和列表,字典的索引是键
,而列表和元组则是 0、1、2等数值
。
info = { "age":12, "status":True, "name":"武沛齐"}
print( info["age"] ) # 输出:12
print( info["name"] ) # 输出:武沛齐
print( info["status"] ) # 输出:True
print( info["xxxx"] ) # 报错,通过键为索引去获取之后时,键不存在会报错(以后项目开发时建议使用get方法根据键去获取值)
value = info.get("xxxxx") # None
print(value)
13. 根据键 修改值 和 添加值 和 删除键值对
info = {"age":12, "status":True,"name":"武沛齐"}
info["gender"] = "男" # 增加键值对
info["age"] = "18" # 修改值
del info["age"] # 删除info字典中键为age的那个键值对(键不存在则报错)
14. for循环
info = {"age":12, "status":True,"name":"武沛齐"}
for item in info: ----> for key,value in info.items(): # 循环键值对
for item in info.key(): # 循环键
for item in info.values(): # 循环值
本文来自博客园,作者:wq512,转载请注明原文链接:https://www.cnblogs.com/wangqi512/p/15120844.html