List

The list is not just a list but can also be used as a stack or a queue.

[ ] create lists with block quotes
Its contents are objects of whatever type you like, separated by commas
can access the individual elements

数组只能包含一种数据类型，list 可以包含不同的数据类型

对 List 的操作

Creat

list()
l1=[1,2,[True,'str'],{'name':'non'}]

l1=[0] * 4  # 初始化一个长度为4的list
l2=[]

Index

my_list=[1,2,3]
my_list[1]  # 2 
my_list[-1]  # 3 the last element   
my_list[-2]  # 2 the 2nd last element


l1=[1,2,[4,5]]
l1[2]  # [4,5]
l1[2][1]  # 5 

l1[0]=400  #l1= [400 ,2,[4,5]]

a = [3, 5, 7, 9]

# 判断元素是否在list中，并得到索引
x = 7  # 查找元素
if x in a:
    idx = a.index(x)
    print(f"{x} 在索引位置 {idx}")
else:
    print(f"{x} 不在列表中")
    
    
# 得到所有索引
a = [3, 5, 7, 5, 9, 5]
x = 5
idx_list = [i for i, val in enumerate(a) if val == x]
print(idx_list)  # [1, 3, 5]

Loop Over

my_list = [1, 2, 3, 4, 5]
for n in my_list:
	print(n)

Add

my_list = [1, 2] 
my_list.append('a')  # [1, 2, 'a']

l1 = [1, 2]
l2 = [3, 4]
l3 = l1 + l2   # [1, 2, 3, 4]

l1.extend(l2)
#  l1  [1, 2, 3, 4]
#  l2  [3, 4]

Remove

pop() method removes and returns value
移除指定索引的元素，并返回该元素的值
未指定参数时，默认弹出最后一个元素

del removes it without returning anything
移除特定索引的元素（不会返回值）

remove() remove a specific value
移除特定值的元素

clear() remove all items
清除所有的元素

使用 Set 移除重复的元素

my_list = [1, 2, 3, 4, 5] 
my_list.pop()   #  5 
# my_list =[1, 2, 3, 4] 

my_list.pop(0)  # 1 
# my_list =[2, 3, 4] 

my_list = [1, 2, 3, 4, 5]
del my_list[0]
#  my_list   [2, 3, 4, 5]

my_list = [1, 2, 3, 2, 5]
my_list.remove(2)  # [1, 3, 2, 5]
my_list.remove(2)  # [1, 3, 5]

my_list.clear()  # []


my_list = [1, 2, 2,2, 3, 5] 
list(set(my_list))  # [1, 2, 3, 5]

Sort

list.sort() 在原数组上排序（修改原数组） 不会返回任何值！！！是对原数组的操作
list_sorted= sorted(list) 返回新 list，而不修改原 list
默认升序排列，均可设置 reverse=True 降序排列

my_list = [10, 2, 5, 4, 2] 
my_list.sort() 
my_list  # [2, 2, 4, 5, 10] 

my_list.sort(reverse=True)
my_list  #  [10, 5, 4, 2, 2] 
sorted(my_list)  # [2, 2, 4, 5, 10]

sheep_sorted = sorted(sheep, reverse=True)

Slicing

my_list[start:stop:step]

start is the first element position to include
stop is exclusive, meaning that the element at position stop won’t be included.
step is the step size. more on this later.
start, stop, and step are all optional.
Negative values can be used too.

my_list = [1, 2, 3, 4, 5, 6, 7, 8] 
my_list[0:3]   # [1, 2, 3] 
my_list[:3]    # [1, 2, 3] 
my_list[4:]    # [5, 6, 7, 8]
my_list[::2]   # [1, 3, 5, 7]
my_list[-1:-3:-1]  # [8,7]

Reverse

lst = [1, 2, 3, 4] 
lst.reverse() 
lst  # [4, 3, 2, 1] 

lst[::-1]  # [4, 3, 2, 1] 
lst  # [1, 2, 3, 4]  

rev = reversed(lst)  # [4, 3, 2, 1]