Detailed introduction to list operations in python (example)

This article brings you a detailed introduction (example) about list operations in python. It has certain reference value. Friends in need can refer to it. I hope it will be helpful to you.

Lest (list):

Definition and creation of lists:

List: is one of the most commonly used data structures in python and other languages. Python uses [] to parse lists
Lists are mutable. --You can change the contents of the list
You can use slices

a=['张三','李四','王五','赵六']

To add, delete, and modify the list:

1: Check ([])

a=['张三','李四','王五','赵六']
print(a[1:3])#左边取到，右边取不到
print(a[-1])
print(a[3:1:-1])
>>['李四', '王五']
>>赵六
>>['赵六', '王五']

2: Add (append, insert)
append can only insert the object to the end of the list
insert can specify the position where the object is inserted

a=['张三','李四','王五','赵六']
a.append('chen')
a.insert(2,'zheng')
print(a)
>>['张三', '李四', 'zheng', '王五', '赵六', 'chen']

3: Change (reassign)

a=['张三','李四','王五','赵六']
a[2]='刘六'
a[0:2]=['chen','zheng']
print(a)
>>['chen', 'zheng', '刘六', '赵六']

4: Delete (remove, del, pop)

a=['张三','李四','王五','赵六']
a.remove('王五')
del a[1]
print(a.pop(1))   #pop是有一个返回值的
print(a)
>>赵六
>>['张三']

Common operations:

#count counts the number of times an element appears in the list

a=['to','too','or','not','to'].count('to')
print(a)
>>2

#extend appends multiple values ​​from another list to the end of the list at once.

a=['to','too','or','not','to']
b=[1,2,3,4,5]
a.extend(b)
print(a)
>>['to', 'too', 'or', 'not', 'to', 1, 2, 3, 4, 5]

#index is used to find the index position of the first matching item of a value from the list

a=['张三','李四','王五','赵六']
print(a.index('王五'))
>>2

#reverse stores the list in reverse

a=['张三','李四','王五','赵六']
a.reverse()
print(a)
>>['赵六', '王五', '李四', '张三']

#sort is used to sort the list at the original position

a=[4,3,63,25,46,54]
a.sort()
print(a)
>>[3, 4, 25, 46, 54, 63]

1. Shallow copy can only copy the outermost layer. If the inner layer is modified, both the original list and the new list will change.

2. Deep copy refers to completely cloning the original list into a new one.

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