常见数据结构-list列表

星哥玩云

发布于 2022-08-19 15:20:21

5980

发布于 2022-08-19 15:20:21

文章被收录于专栏：开源部署

一、什么情况下使用列表？

思考存储5个人的年龄，求他们的平均值

age1 = <span class="hljs-number">18</span>
age2 = <span class="hljs-number">19</span>
age3 = <span class="hljs-number">20</span>
age4 = <span class="hljs-number">21</span>
age5 = <span class="hljs-number">22</span>

思考存储100个人的年龄
解决使用列表

二、基本使用

本质是一个有序集合
创建列表

<span class="hljs-string">'''
创建列表
    格式：列表名 = [元素1, 元素2, ……, 元素n]
'''</span>
<span class="hljs-comment"># 创建空列表</span>
li1 = []
print(li1, type(li1))

<span class="hljs-comment"># 创建带有元素的列表</span>
<span class="hljs-comment"># 注意：列表中元素的类型可以不同，但是在今后的开发中一般不存在这种状况</span>
li2 = [<span class="hljs-number">1</span>, <span class="hljs-number">2</span>, <span class="hljs-number">3</span>, <span class="hljs-number">4</span>, <span class="hljs-number">5</span>, <span class="hljs-string">"good"</span>, <span class="hljs-keyword">True</span>]
print(li2)

列表元素的访问

<span class="hljs-comment"># 列表元素的访问</span>
li3 = [<span class="hljs-number">1</span>,<span class="hljs-number">2</span>,<span class="hljs-number">3</span>,<span class="hljs-number">4</span>,<span class="hljs-number">5</span>]
<span class="hljs-comment"># 往列表末尾添加元素</span>
li3.append(<span class="hljs-number">6</span>)
<span class="hljs-comment"># 获取元素  列表名[下标]</span>
print(li3[<span class="hljs-number">2</span>])
<span class="hljs-comment"># print(li3[9]) #下标超出范围，溢出</span>
<span class="hljs-comment"># print(li3[-1]) # 下标可以是负数，-1表示最后一个元素的下标，-2表示倒数第二个，依次类推</span>
<span class="hljs-comment"># 修改元素 列表名[下标] = 值</span>
li3[<span class="hljs-number">2</span>] = <span class="hljs-number">33</span>
<span class="hljs-comment"># li3[6] = 10 #下标不存在</span>
print(li3)
<span class="hljs-comment"># 截取列表</span>
print(li3[<span class="hljs-number">1</span>:<span class="hljs-number">3</span>])
print(li3[<span class="hljs-number">1</span>:])
print(li3[:<span class="hljs-number">3</span>])

列表操作

<span class="hljs-comment"># 列表相加（列表组合）</span>
li4 = [<span class="hljs-number">1</span>,<span class="hljs-number">2</span>,<span class="hljs-number">3</span>]
li5 = [<span class="hljs-number">4</span>,<span class="hljs-number">5</span>,<span class="hljs-number">6</span>]
li6 = li4 +li5
print(li6)

<span class="hljs-comment"># 列表相乘（列表重复）</span>
li7 = [<span class="hljs-number">7</span>,<span class="hljs-number">8</span>,<span class="hljs-number">9</span>]
li8 = li7 * <span class="hljs-number">3</span>
print(li7)
print(li8)

<span class="hljs-comment"># 成员判断</span>
li9 = [<span class="hljs-number">1</span>,<span class="hljs-number">2</span>,<span class="hljs-number">3</span>]
print(<span class="hljs-number">1</span> <span class="hljs-keyword">in</span> li9)
print(<span class="hljs-number">4</span> <span class="hljs-keyword">in</span> li9)

三、二维列表

概念：列表中的元素是一位列表的列表

本质：一维列表

li1 = [[<span class="hljs-number">1</span>,<span class="hljs-number">2</span>,<span class="hljs-number">3</span>],
        [<span class="hljs-number">4</span>,<span class="hljs-number">5</span>,<span class="hljs-number">6</span>],
        [<span class="hljs-number">7</span>,<span class="hljs-number">8</span>,<span class="hljs-number">9</span>]]

print(li1[<span class="hljs-number">1</span>][<span class="hljs-number">1</span>])

四、内置功能

append(obj) 在列表的末尾添加一个新的元素

li1 = [<span class="hljs-number">1</span>,<span class="hljs-number">2</span>,<span class="hljs-number">3</span>,<span class="hljs-number">4</span>,<span class="hljs-number">5</span>]
li1.append(<span class="hljs-number">6</span>)
li1.append([<span class="hljs-number">7</span>,<span class="hljs-number">8</span>,<span class="hljs-number">9</span>])
print(li1)

extend(seq) 在列表的末尾一次追加多个元素

li2 = [<span class="hljs-number">1</span>,<span class="hljs-number">2</span>,<span class="hljs-number">3</span>,<span class="hljs-number">4</span>,<span class="hljs-number">5</span>]
li2.extend([<span class="hljs-number">6</span>,<span class="hljs-number">7</span>,<span class="hljs-number">8</span>])
print(li2)

insert(index, obj) 将元素obj按下标插入列表，不会覆盖原数据，原数据会按顺序后移

li3 = [<span class="hljs-number">1</span>,<span class="hljs-number">2</span>,<span class="hljs-number">3</span>,<span class="hljs-number">4</span>,<span class="hljs-number">5</span>]
li3.insert(<span class="hljs-number">2</span>, <span class="hljs-number">100</span>)
print(li3)

pop(index=-1) 移除列表中指定下标出的元素，默认移除最后一个，返回被删掉的数据

li4 = [<span class="hljs-number">1</span>,<span class="hljs-number">2</span>,<span class="hljs-number">3</span>,<span class="hljs-number">4</span>,<span class="hljs-number">5</span>]
data = li4.pop()
print(data, li4)

remove(obj) 移除列表中第一次出现的obj元素

li5 = [<span class="hljs-number">1</span>,<span class="hljs-number">2</span>,<span class="hljs-number">3</span>,<span class="hljs-number">4</span>,<span class="hljs-number">5</span>,<span class="hljs-number">2</span>,<span class="hljs-number">4</span>,<span class="hljs-number">2</span>,<span class="hljs-number">5</span>,<span class="hljs-number">6</span>,<span class="hljs-number">7</span>]
li5.remove(<span class="hljs-number">2</span>)
print(li5)

clear() 清空列表

li6 = [<span class="hljs-number">1</span>,<span class="hljs-number">2</span>,<span class="hljs-number">3</span>,<span class="hljs-number">4</span>,<span class="hljs-number">5</span>]
li6.clear()
print(li6)

count(obj) 返回元素obj在列表中出现的次数

li7 = [<span class="hljs-number">1</span>,<span class="hljs-number">2</span>,<span class="hljs-number">3</span>,<span class="hljs-number">4</span>,<span class="hljs-number">5</span>,<span class="hljs-number">2</span>,<span class="hljs-number">4</span>,<span class="hljs-number">2</span>,<span class="hljs-number">5</span>,<span class="hljs-number">6</span>,<span class="hljs-number">7</span>]
print(li7.count(<span class="hljs-number">2</span>))

len(seq) 返回列表中元素的个数

li8 = [<span class="hljs-number">1</span>,<span class="hljs-number">2</span>,<span class="hljs-number">3</span>,<span class="hljs-number">4</span>,<span class="hljs-number">5</span>]
print(len(li8))

index(obj) 在列表中获取元素第一次出现的下标，没有则会抛出ValueError异常

li9 = [1,2,3,4,5,2,4,2,5,6,7]
print(li9.index(2))

max(seq) 返回列表中最大的元素

print(max([2,3,4,1,4,6,7,3]))

min(seq) 返回列表中最小的元素
reverse() 列表倒序

li10 = [<span class="hljs-number">1</span>,<span class="hljs-number">2</span>,<span class="hljs-number">3</span>,<span class="hljs-number">4</span>,<span class="hljs-number">5</span>]
li10.reverse()
print(li10)

sort() 根据func函数给定的规则进行列表元素的排序，默认升序

li11 = [<span class="hljs-number">2</span>,<span class="hljs-number">1</span>,<span class="hljs-number">3</span>,<span class="hljs-number">5</span>,<span class="hljs-number">4</span>]
li11.sort()
print(li11)

list(seq) 将其他类型的集合转为列表类型

str1 = "baism"
li12 = list(str1)
print(li12, type(li12))

五、内存问题

赋值
- ==与is

num1 = <span class="hljs-number">1</span>
num2 = <span class="hljs-number">1</span>
print(id(num1), id(num2))
print(num1 == num2)
print(num1 <span class="hljs-keyword">is</span> num2)
num3 = <span class="hljs-number">401</span>
num4 = <span class="hljs-number">401</span>
print(id(num3), id(num4))
print(num3 == num4)
print(num3 <span class="hljs-keyword">is</span> num4)

a = [<span class="hljs-number">1</span>,<span class="hljs-number">2</span>,<span class="hljs-number">3</span>,<span class="hljs-number">4</span>,<span class="hljs-number">5</span>]
b = a
print(id(a), id(b))
print(a == b)
print(a <span class="hljs-keyword">is</span> b)

c = [1,2,3,4,5,[7,100,9]]
d = c
print(c == d)
print(c is d)
c[5][0] = 60
print(c)
print(d)

浅拷贝只拷贝表层元素

<span class="hljs-keyword">from</span> copy <span class="hljs-keyword">import</span> copy

a = [<span class="hljs-number">1</span>,<span class="hljs-number">2</span>,<span class="hljs-number">3</span>,<span class="hljs-number">4</span>,<span class="hljs-number">5</span>]
b = copy(a)
print(id(a), id(b))
print(a == b)
print(a <span class="hljs-keyword">is</span> b)

c = [<span class="hljs-number">1</span>,<span class="hljs-number">2</span>,<span class="hljs-number">3</span>,[<span class="hljs-number">4</span>,<span class="hljs-number">5</span>,<span class="hljs-number">6</span>]]
d = copy(c)
print(id(c), id(d))
print(c == d)
print(c <span class="hljs-keyword">is</span> d)
print(id(c[<span class="hljs-number">3</span>]), id(d[<span class="hljs-number">3</span>]))
print(c[<span class="hljs-number">3</span>] == d[<span class="hljs-number">3</span>])
print(c[<span class="hljs-number">3</span>] <span class="hljs-keyword">is</span> d[<span class="hljs-number">3</span>])

深拷贝注意：不论深拷贝还是浅拷贝都会在内存中生成一片新的内容空间(把拷贝的内容在内存中重新创建一份) 两者有区别的前提：元素中有另外的列表说明：深拷贝在内存中重新创建所有子元素

<span class="hljs-keyword">from</span> copy <span class="hljs-keyword">import</span> deepcopy

a = [<span class="hljs-number">1</span>,<span class="hljs-number">2</span>,<span class="hljs-number">3</span>,<span class="hljs-number">4</span>,<span class="hljs-number">5</span>]
b = deepcopy(a)
print(id(a), id(b))
print(a == b)
print(a <span class="hljs-keyword">is</span> b)

c = [<span class="hljs-number">1</span>,<span class="hljs-number">2</span>,<span class="hljs-number">3</span>,<span class="hljs-number">4</span>,<span class="hljs-number">5</span>,[<span class="hljs-number">6</span>,<span class="hljs-number">7</span>,<span class="hljs-number">8</span>]]
d = deepcopy(c)
print(id(c), id(d))
print(c == d)
print(c <span class="hljs-keyword">is</span> d)
print(id(c[<span class="hljs-number">5</span>]), id(d[<span class="hljs-number">5</span>]))
print(c[<span class="hljs-number">5</span>] == d[<span class="hljs-number">5</span>])
print(c[<span class="hljs-number">5</span>] <span class="hljs-keyword">is</span> d[<span class="hljs-number">5</span>])