How to use lists in python

How to use lists in Python: 1. To access the values ​​in the list, use subscript index to access the values ​​in the list; 2. Update the list and use the [append()] method to add list items; 3. To delete elements from a list, you can use the del statement to delete elements from the list.

How python uses lists:

Sequence is the most basic data structure in Python. Each element in the sequence 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.

• List is the most commonly used Python data type, which can appear as a comma-separated value within square brackets.

• The data items of the list do not need to be of the same type

To create a list, just separate the different data items with commas using square brackets Just enclose it. It looks like this:

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

Like string indexing, list indexing starts at 0. Lists can be intercepted, combined, etc.

Accessing values ​​in the list

Use subscript index to access the value in the list. You can also use square brackets to intercept characters, as shown below:

Example (Python 2.0)

#!/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 result of the above example:

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

Update list

You can update the data of the list To modify or update an item, you can also use the append() method to add a list item, as shown below:

Example (Python 2.0)

#!/usr/bin/python
# -*- coding: UTF-8 -*-
 
list = []          ## 空列表
list.append('Google')   ## 使用 append() 添加元素
list.append('Runoob')
print list

Note: We will discuss this in the next chapter Discuss the use of the append() method

Output results of the above examples:

['Google', 'Runoob']

Delete list elements

You can use the del statement to delete elements of the list, The following example:

Example (Python 2.0)

#!/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:

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

Related free learning recommendations: python video tutorial

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