列表的增删改查

a="  6    "   int(a)==6 转换之后相当于去空格

一、增加

　　append 在列表最后以为增加一个元素。

　　

li=["a","d","ffsd",5,"gds"]
li.append("ad")  
print(li)  #输出["a","d","ffsd",5,"gds","ad"]

li.append("fsda","ada","da")
print(li)# 报错

li.append(["a","ds","faw"])
print(li)#["a","d","ffsd",5,"gds",["a","ds","faw"]]

#输入员工姓名，输入完成后 输入Q退出，不区分大小写
while True:
    username=input("请输入员工姓名：")
    if username.upper()==Q:
        break
    li.append(username)
print(li)

 

二、插入 insert

　　li.inset(2,"d")   2表示要插入的位置，“d“表示要插入的元素

li=["a","d","ffsd",5,"gds"]
li.insert(1,"f")
print(li)
# ["a","f","d","ffsd",5,"gds"]

三、迭代添加 extend

　　

li=["a","d","ffsd",5,"gds"]
li.extend("e")
print(li)
#li=["a","d","ffsd",5,"gds","e"]

li.extend("abc")
print(li)
#li=["a","d","ffsd",5,"gds","a","b","c”]

li.extend(["ajafa","bgsd","afc"])
print(li)
li=["a","d","ffsd",5,"gds","ajafa","bgsd","afc"]

 

四、删除

　　1、pop 按索引删除

　　　　

li=["a","d","ffsd",5,"gds"]
name=li.pop(2)
print(name)  #输出  删除的元素ffsd
print(li)
#["a","d",5,"gds"]

　　2、remove  按元素删除

　　　　

li=["a","d","ffsd",5,"gds"]
name=li.remove("d")
print(name)   #None
print(li)      #["a","ffsd",5,"gds"]
#remove一次只能删除一个元素。

#例子删除列表中的多个a
li=[2,6,"a","sd",2,"a",8","a"]
for i in li:
    if i == "a":
        li.remove("a")
print(li)

　　3、clear 清空列表

　　　　

li=["a","d","ffsd",5,"gds"]
li.clear()
print(li)
#[]   清空li中所有元素

　　4、del 删除， 单删，切片删

　　　　

li=["a","d","ffsd",5,"gds"]
del li[1]
print(li)
#["a","ffsd",5,"gds"]

del li[1:3]
print(li)
#["a",5,"gds"]

del li[0::2]
print(li)
#["a","ffsd","gds"]

del li #删除列表
print(li)# 报错

五、改 

　　单改： li

　　li=["a","d","ffsd",5,"gds"]

　　li[1]="aaa"

　　print(li) 

　 输出　["a","aaa","ffsd",5,"gds"]

li=["a","d","ffsd",5,"gds"]
li[0:3]="你好"
print(li)
#["你”,“好",5,"gds"]

li[0:3]=["你好"，“哈哈”]
print（li）
#["你好",“哈哈”,5,"gds"]

六、查

　#　

li=["a","d","ffsd",5,"gds"]

　print（li）

#["a","d","ffsd",5,"gds"]

print（li[1]）
# d
print(li[0:3])
#["a","d","ffsd"]

输出所有元素
for i in li:
　　print(i)

@ q=[1,2,3,[4,5,6]7,8]

　　q[1]       2

　　q[3]       [4,5,6]

　　q[3][1]     5

 

count  计算个数

　　q=["a","s","d",["a","s"],”ed“]

　　q.count(“a”)  

　　输出1

正序，翻转，逆序

　　

q=[1,5,3,9,2,6,8,7]　　
#正序：sort
q.sort()
print(q)
#[1, 2, 3, 5, 6, 7, 8, 9]

#翻转：reverse
q.reverse()
print(q)
#[7, 8, 6, 2, 9, 3, 5, 1]

#逆序
q.sort()
q.reverse()
print(q) 
#[9, 8, 7, 6, 5, 3, 2, 1]
q.sort(reverse=True)
print(q)
#[9, 8, 7, 6, 5, 3, 2, 1]

七、元祖 typle()

　　t=

t=(1,2,3,"asd","s","True",["a","s"],("a","s"))
#只能读，不能改，唯一可改的是元祖内部的列表内的元素，单列表不能消失

#索引
print(t[2])
# 3
print(t[0:3])
#(1,2,3)

八、range 范围 相当于可迭代对象

　　

for i in range(0,10):
    print(i)
0
1
2
3
4
5
6
7
8
9
#步长和反向
for i in range(0,10,-2):
    print(i)
#没有输出也没有报错
for i in range(10，0，-2):
    print(i)
10
8
6
4
2