Python list (List) operation methods

This article mainly introduces the detailed operation method of list (List) in Python, including creation, access, update, deletion, other operations, etc. Friends who need it can refer to it

List is the most popular list in Python The basic data structure, list is the most commonly used Python data type, and 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. Additionally, 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. As shown below:

Copy code The code is as follows:

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. Similarly, you can also use square brackets to intercept characters, as shown below:

Copy code The code is as follows:

#!/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]

The output result of the above example:

Copy code The code is as follows:

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

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

Copy code The code is as follows:

#!/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];

The output result of the above example:

Copy code The code is as follows:

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

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

Copy code The code is as follows:

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

The output result of the above example:

Copy code The code is as follows:

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

5. Python list script operator
The operators for list pairs and * are similar to strings. The symbol is used for combined lists, and the * symbol is used for repeated lists.

is as follows:

##Python expressionResultDescriptionlen([1, 2, 3])3Length[1, 2, 3] [4, 5, 6][1, 2, 3, 4, 5, 6]combination['Hi!'] * 4['Hi!', 'Hi!', 'Hi!', 'Hi!']Repeat3 in [1, 2, 3]TrueWhether the element exists in the listfor x in [1, 2, 3]: print x,1 2 3Iteration

6 , Python list interceptionPython's list interception and string operation types are as follows:

Copy code The code is as follows:

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

Operation:

Python expressionResultDescriptionL[2]'SPAM!'Read the third element in the listL[-2]'Spam'Read the second to last element in the listL[1:]['Spam', 'SPAM!']Truncate the list starting from the second element

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

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Detailed explanation of functions & methods in Python lists

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