python字典的增删改查，嵌套

1.字典创建常用的三种方法

dic=dict({“frj”:1})
print(dic)

dic = dict(one =1,two = 2 ,three =3)
print(dic)

dic = dict(((“one”,1),(“two”,2)))
print(dic)

dic = dic{[1,2,3]:“frj”,“two”:3} #列表可变，所以不可哈希
print(dic)

2.字典的增删改查
#增:
dic = {1:“f”,1:“dd”,2:3} #一个键可以对应多个值,键必须唯一,而 值可以有多个
print(dic)
{1: ‘dd’, 2: 3}

dic [“杰ray”] = “男”
print(dic)
{1: ‘dd’, 2: 3, ‘杰ray’: ‘男’}

#有则改之,无则加冕
dic [2] = “男”
print(dic)
{1: ‘dd’, ‘2’: ‘男’}

#setdefault #有则不变,无则加勉
dic.setdefault(“hobby”,“篮球”)
print(dic)

#删
dic = {1:“f”,3:“dd”,2:3}
pop按照键去删除键值对,有返回值,可设置第二个参数则字典中是否有此值都不会报错
dic.pop(1)
print(dic)

ret = dic.pop()

ret = dic.pop(4,“无”)
print(ret)
print(dic)

#清空 clear
dic = {1:“f”,1:“dd”,2:3}
dic.clear()
print(dic)

#del
del dic[1] #如果没有键,则会报错,推荐使用pop
print(dic)

#改
dic = {1:“f”,1:“dd”,2:3}
dic[1] = “eee”
print(dic）

#查
dic = {1:“f”,4:“dd”,2:3}
print(dic[1])

l1 = dic.get(4)
print(l1)

l2 = dic.get(5,“没有”)
print(l2)

#特殊 key value items
dic = {1:“f”,4:“dd”,2:3}
print(dic.keys(),type(dic.keys()))
print(dic.values())
print(list(dic.keys()))

for key in dic.keys:
print(key)

for i in dic.items():
print(i) #i是元组(1, ‘f’)(4, ‘dd’)(2, 3)

for keys,value in dic.items():
print(keys,value)

#字典的嵌套
dic = {1: “f”,
4: {“dasda”:34532,“asdas”:1234},
2: [2, 3, 4,{“十大”:1233,“dasda”:34532,“asdas”:1234}]}

print(dic.get(2)[3][“dasda”])