python---列表详解

1.ctrl + d复制一行

列表的特点：可以存取多个值

需要了解的:

 

2.sort：数字排第一位，字母，汉字(列表里面需要是相同的数据类型)

Eg:

l1 = ['你好','a','c','b','d','1','3','2']

l1.sort()

print(l1)

['1', '2', '3', 'a', 'b', 'c', 'd', '你好']

 

3.index获取b元素的下标

l1 = ['你好','a','c','b','d','1','3','2']

res = l1.index('b')

print(res)

3

 

4.clear清空列表里面所有元素

l1 = ['你好','a','c','b','d','1','3','2']

l1.clear()

print(l1)

[]

 

5.copy复制一个列表

eg:

l1 = ['你好','a','c','b','d','1','3','2']

res = l1.copy()

print(res)

['你好', 'a', 'c', 'b', 'd', '1', '3', '2']

 

6.reverse倒序

l1 = ['你好','a','c','b','d','1','3','2']

l1.reverse()

print(l1)

['2', '3', '1', 'd', 'b', 'c', 'a', '你好']

#必须要掌握的

 

7.insert 在下标为3的地方插入一个元素

eg:

l1 = ['a','a','b','c','d']

l1.insert(3,[1,2,3])

 print(l1)

['a', 'a', 'b', [1, 2, 3], 'c', 'd']

 

8.统计列表当中a元素的个数

eg:

l1 = ['a','a','b','c','d']

res = l1.count('a')

print(res)

2

 

9.append在元素列表最后面追加元素

l1 = ['a','a','b','c','d']

l1.append('aaaa')

l1.append('bbbb')

print(l1)

['a', 'a', 'b', 'c', 'd', 'aaa', 'bbb']

 

10.remove删除指定元素

eg:

l1 = ['a','a','b','c','d']

l1.remove('a')

print(l1)

['a', 'b', 'c', 'd']

 

11.pop是取出指定下标的元素

eg:

l1 = ['a','a','b','c','d']

res = l1.pop(0)

print(l1)

print(res)

 

12.extend添加列表，元组等是添加的列表，元组里面单个值

l1 = ['a','a','b','c','d']

l1.extend({'ss':11,'dd':22,'mm':33})

print(l1)

['a', 'a', 'b', 'c', 'd', 'ss', 'dd', 'mm']

 

1. 列表也是可以切片，也有索引或者下标

eg: 

l1 = ['a','a','b','c','d']

print(l1[4])

print(l1[-2])

print(l1[2:4])

d

c

['b', 'c']

 

14.列表利用下标改值

eg:

l1 = ['a','a','b','c','d']

l1[1] = 'ss'

print(l1)

['a', 'ss', 'b', 'c', 'd']