Detailed explanation of Python list (List) operation methods

List is the most basic data structure in Python. List is the most commonly used Python data type. The data items of the list do not need to be of the same type. Each element in the list is assigned a number - its position, or index, with the first index being 0, the second index being 1, and so on.
Python has 6 built-in types for sequences, but the most common are lists and tuples. Operations that can be performed on sequences include indexing, slicing, adding, multiplying, and checking members. In addition, Python has built-in methods for determining the length of a sequence and determining the largest and smallest elements.

1. Create a list
Just enclose the different data items separated by commas in square brackets. It looks like this:

list1 = ['physics', 'chemistry', 1997, 2000];
list2 = [1, 2, 3, 4, 5 ];
list3 = ["a", "b", "c", "d"];

Like the indexing of strings, list indexing starts from 0. Lists can be intercepted, combined, etc.
2. Access the values ​​in the list
Use subscript index to access the values ​​in the list. You can also use square brackets to intercept characters, as shown below:

#!/usr/bin/python

list1 = ['physics', 'chemistry', 1997, 2000];
list2 = [1, 2, 3, 4, 5, 6, 7 ];
print "list1[0]: ", list1[0]
print "list2[1:5]: ", list2[1:5]

Output of the above example Result:

list1[0]:  physics
list2[1:5]:  [2, 3, 4, 5]

3. Update the list
You can modify or update the data items of the list. You can also use the append() method to add list items, as shown below:

#!/usr/bin/python
list = ['physics', 'chemistry', 1997, 2000];
print "Value available at index 2 : "
print list[2];
list[2] = 2001;
print "New value available at index 2 : "
print list[2];

Output result of the above example:

Value available at index 2 :
1997
New value available at index 2 :
2001

IV. Delete list elements
You can use the del statement to delete elements of the list, as shown in the following example:

#!/usr/bin/python
list1 = ['physics', 'chemistry', 1997, 2000];
print list1;
del list1[2];
print "After deleting value at index 2 : "
print list1;

Output result of the above example:

['physics', 'chemistry', 1997, 2000]
After deleting value at index 2 :
['physics', 'chemistry', 2000]

5. Python list script operators
The list operators + and * are similar to string operators. The + sign is used for combined lists, and the * sign is used for repeated lists.

As shown below:

#6. Python list interception
Python's list interception and string operation types are as follows:

L = ['spam', 'Spam', 'SPAM!']

Operation:

7. Functions and methods of Python list operations
List operations include the following functions:
1, cmp(list1 , list2): Compare the elements of two lists
2. len(list): The number of list elements
3. max(list): Return the maximum value of the list elements
4. min(list): Return Minimum value of list elements
5. list(seq): Convert tuples to lists
List operations include the following methods:
1. list.append(obj): Add a new object at the end of the list
2. list.count(obj): Count the number of times an element appears in the list
3. list.extend(seq): Append multiple values ​​from another sequence at the end of the list at once (use a new list Expand the original list)
4. list.index(obj): Find the index position of the first matching item of a certain value from the list
5. list.insert(index, obj): Insert the object List
6, list.pop(obj=list[-1]): Remove an element in the list (default is the last element), and return the value of the element
7, list.remove(obj) : Remove the first matching item of a value in the list
8. list.reverse(): Reverse the elements in the list
9. list.sort([func]): Sort the original list

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