Python lists (list)

The sequence is the most basic data structure in Python. Each element in the sequence is assigned a number-its position, or index, the first index is 0, the second index is 1, and so on.

Python has 6 built-in types of sequences, but the most common are lists and tuples.

Sequences can be performed by operations including indexing, slicing, adding, multiplying, and checking members.

In addition, Python has built-in methods for determining the length of a sequence and determining the maximum and minimum elements.

A list is the most commonly used Python data type and can appear as a comma-separated value within a square bracket.

Data items for a list do not need to have the same type

Create a list by enclosing separate data items separated by commas in square brackets. As shown below:

List1 = [' Physics ', ' Chemistry ', 1997, 2000];

List2 = [1, 2, 3, 4, 5];

LIST3 = ["A", "B", "C", "D"];

As with the index of a string, the list index starts at 0. Lists can be intercepted, combined, and so on.

Accessing values in a list

Use the subscript index to access the values in the list, and you can also use square brackets to intercept the characters 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 result of the above example output:

List1[0]: Physics

List2[1:5]: [2, 3, 4, 5]

Update list

You can modify or update the list's data items, or you can use the Append () method to add the list items 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];

Note: We will discuss the use of the Append () method in the following chapters

The result of the above example output:

Value available at index 2:

1997

New value available at index 2:

2001

To delete a list element

You can use the DEL statement to delete the elements of a list, as 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;

The result of the above example output:

[' Physics ', ' Chemistry ', 1997, 2000]

After deleting value at index 2:

[' Physics ', ' chemistry ', 2000]

Note: We will discuss the use of the Remove () method in the following chapters

Python List script operators

The operands of the list to + and * are similar to strings. The + sign is used for the combined list, and the * number is used for repeating lists.

As shown below:

Python expressions

Results

Describe

Len ([1, 2, 3]) 3 length

[1, 2, 3] + [4, 5, 6] [1, 2, 3, 4, 5, 6] combination

[' hi! '] * 4 [' hi! ', ' hi! ', ' hi! ', ' hi! '] repeat

3 in [1, 2, 3] True whether the element exists in the list

For x in [1, 2, 3]: print x, 1 2 3 iterations

Python list interception

The list of Python intercepts the type of string manipulation as follows:

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

Operation:

Python expressions

Results

Describe

L[2] ' spam! ' reads the third element of the list

L[-2] ' Spam ' reads the second-to-last element in a list

L[1:] [' Spam ', ' spam! '] starting with the second element to intercept a list

Python list Functions & methods

Python contains the following functions:

Serial number

Function

1 cmp (List1, List2)
Compare two elements of a list

2 len (list)
Number of list elements

3 Max (list)
Returns the maximum value of a list element

4 min (list)
Returns the minimum value of a list element

5 list (SEQ)
Convert a tuple to a list

Python contains the following methods:

Serial number

Method

1 list.append (obj)
Add a new object at the end of the list

2 List.count (obj)
Count the number of occurrences of an element in a list

3 List.extend (SEQ)
Append multiple values from another sequence at the end of the list (extend the original list with a new list)

4 List.index (obj)
Find the index position of the first occurrence of a value from the list

5 List.insert (index, obj)
Inserting an object into a list

6 List.pop ([index])
Removes an element from the list (the last element by default), and returns the value of the element

7 List.remove (obj)
To remove the first occurrence of a value in a list

8 List.reverse ()
Reverse List of elements

9 List.sort ([func])
Sort the original list

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