python疑問(wèn)4：list，tuple，dict，set區(qū)分

U2FsdGVkX1x 發(fā)布于2019-07-30 15:36 / 2584人閱讀

摘要：需要注意的是的必須是不可變對(duì)象。因?yàn)楦鶕?jù)來(lái)計(jì)算的存儲(chǔ)位置，如果每次計(jì)算相同的得出的結(jié)果不同，那內(nèi)部就完全混亂了。這個(gè)通過(guò)計(jì)算位置的算法稱為哈希算法。要保證的正確性，作為的對(duì)象就不能變。

1.List
定義一個(gè)列表，列表內(nèi)容數(shù)據(jù)類(lèi)型可以不同，元素可以更改，可以嵌套list

//定義
name = ["Tom","Jack","Marry"]
//長(zhǎng)度計(jì)算
len(name) // Out:3
//訪問(wèn)列表內(nèi)元素
name[0]//Tom
name[1]//Jack
name[2]//Marry
//追加元素
name.append("Jim") //["Tom","Jack","Marry","Jim"]
//插入元素
name.insert(1,"pengyu") //["Tom","pengyu","Jack","Marry","Jim"]
//刪除末尾元素
name.pop() //["Tom","pengyu","Jack","Marry"]
//刪除指定位置
name.pop(2) //["Tom","pengyu","Marry"]
//替換元素
name[0] = "haha" //["haha","pengyu","Marry"]

2.tuple
定義一個(gè)元組，一旦初始化不能修改

//定義
phone = ("iphone","ipad","huawei")
//特殊，定義一個(gè)元素的tuple,記得加逗號(hào)，消除與括號(hào)運(yùn)算符的歧義
phone = ("ipad",)
//tuple元素內(nèi)含list
phone = ("iphone","ipad",["huawei","oppo"])
phone[2][0]="iwatch"
phone[2][1]="vivo"
print(phone) // ("iphone","ipad",["iwatch","vivo"])
//定義一個(gè)不變的tuple，必須保證其內(nèi)部元素也是不變的

3.dict
定義一個(gè)字典，內(nèi)含鍵值對(duì)。需要注意的是dict的key必須是不可變對(duì)象。
因?yàn)閐ict根據(jù)key來(lái)計(jì)算value的存儲(chǔ)位置，如果每次計(jì)算相同的key得出的結(jié)果不同，那dict內(nèi)部就完全混亂了。這個(gè)通過(guò)key計(jì)算位置的算法稱為哈希算法（Hash）。

要保證hash的正確性，作為key的對(duì)象就不能變。在Python中，字符串、整數(shù)等都是不可變的,可以作為key,而list是可變的，就不能作為key

//定義
salary = {"xiaoming":2000,"Jim":5000,"Wang":4600}
//訪問(wèn)
salary["Wang"] //4600
//修改
salary["Jim"] = 3200// {"xiaoming":2000,"Jim":3200,"Wang":4600}
//判斷key是否在字典里
"Jack" in salary //False
//刪除key
salary.pop("Wang") //{"xiaoming":2000,"Jim":3200}
//如果key可變？
list = ["a","b","c"]
salary[list] = "pengyu" //報(bào)錯(cuò)

4.set
set定義一個(gè)key的集合，跟dict相似，但不儲(chǔ)存value，key不能重復(fù)，其元素內(nèi)部必須為不可變對(duì)象

//定義
color = set(["red","yellow","blue"]) // {"red","yellow","blue"}
color = set(["red","yellow","blue","red","yellow"]) //{"red","yellow","blue"}
//添加元素
color.add("black") // {"red","yellow","blue","black"}
//刪除元素
color.remove("red") // {"yellow","blue","black"}
//并集,交集
color1 = set(["red","blue","black"])
color2 = set(["yellow","black","red"])
color1 & color2 // {"red","black"}
color1 | color2 // {"red","yellow","blue","black"}