Change List Item in Python

In Python programming, a list is a dynamic data structure containing numerous items within a solitary variable. The characteristics of the list include being a structured, editable, and alterable series of elements. Each entry in a list is referred to as an element. Square brackets ([]) are utilized to create a list.

Properties:

A list maintains a specific sequence that stays constant. As you append new items, they will be positioned after the list. Once formed, you can adjust, incorporate, or eliminate items from the list. Lists may encompass items that possess identical values.

Creating a List

Output:

 ['Java', 'C', 'C++'] 

Explanation

A list of programming languages is created in the above code, named prog_lang. The list has three elements: "Java", "C", and "C++". Then, the print function displays the items in the list.

Access Items Using Index Number

The list data type in Python enables you to get the element from the specified index number for the list. See the below example to understand.

Code

Output:

 C 

Explanation

We have used indexing to access the second element from the list. As the output, "C" will print.

Updating the List Item

You can directly assign a new value to an item's index in a list to change its value. As an illustration, consider this:

Code

Output:

 ['Java', 'Python', 'C++'] 

Explanation

In the above lines of code, the line prog_lang[1] = "Python" will change the element at index 1 in the existing list. The second element, "C", will be replaced with the new value "Python".

Change Item's Range:

To change the range of items, First, create a list with the updated values and reference the index range where the new values are to be inserted. For example:

Code

Output:

 ['Java', 'PHP', 'Swift', 'Python', 'C#', 'FORTRAN'] 

Explanation

The second line of code, line prog_lang[1:3] = ["PHP", "Swift"], will change the value in the given list. It will replace the elements from index number 1 to index number 3 with the new given values "PHP" and "Swift".

Add a New Element to the List

Utilize the insert() method to add an element without changing the existing values. Let's understand with a suitable example:

Code

Output:

 ['Java', 'PHP', 'Kotlin', 'Swift', 'Python', 'C#', 'FORTRAN'] 

Explanation

The line prog_lang.insert(2, "Kotlin") in the above program adds the value "Kotlin" at index number 2 in the given list prog_lang.

Access the List Length

In Python, the len() method is the built-in function to access the length of the given list. However, The len() function is commonly used in various programming languages to access the list's length.

Output:

 3 

Explanation

In the code mentioned above, we have used the len() function to access the length of the given list prog_lang. As there are three items in the list, we got the output 3.

List Data Types

List items can be of any data type, such as strings, integers, and booleans (True/False). A list can have different data types together. For example, see the below code:

Output:

 ['java', 45, False] 

Explanation

We have created a list above, named mixed_list, where we are given the elements of several data types like string, int and boolean, denoting that you can create a list containing more than one data type.

Access the Data Types

Here, using the type() function, we can fetch the data type of the elements from the given list. The type() function is the built-in function in Python that allows us to get the data type of a specified element.

Code

Output:

 <class 'str'> <class 'int'> <class 'bool'> 

Explanation

In the above code, we created a list called mixed_list that has different data type elements, like the string "java", the integer 45, and the boolean value False. After that, we used a loop to access each element by index (0, 1, 2) and print the data type of each element using the type() function.

Changing a List Item

There are several methods to change the list items in Python, such as append(), insert(), and extend() methods; let's discuss these methods one by one and try to understand them with relevant codes.

1. Using .append() method

The append() method is a built-in method in Python that enables us to add an item at the end of the list. The syntax is mentioned here to add an item to the given list:

Syntax

Code

Output

 [5, 7, 8, 4, 9] 

Explanation

In the above code, we have used num_list.append(9), which adds the number 9 to the end of the given list num_list.

2. Using .insert() method

The insert() method adds an element to a specific position within a list. It allows you to specify the index at which you want to add the new item and the element you want to insert. Here's the syntax for the insert() method:

Syntax

Code

Output

 [5, 7, 9, 8, 4] 

Explanation

In the above lines of code, the num_list.insert(2, 9) will insert the number 9 into the num_list at index 2. Here, 2 specifies the indexing number, so 9 is inserted at the third position between 7 and 8.

3. Using .extend() method

Using the extend() method, you can add one list item to the end of another list item. You can use the following syntax to add the elements of another list to a list by going with the extend method:

Syntax

Code

Output:

 [5, 7, 8, 4, 2, 9, 6] 

Explanation

The line in the given code num_list.extend(mynum_list) adds all the elements from mynum_list to the end of num_list.

Slicing

Extracting a segment from a list is called "slicing." This technique can be utilized to alter a specific section of a list. Follow the syntax below to slice a segment of a list:

Syntax

Code

Output:

 [5, 2, 9, 4] 

Explanation

In the above code, the list's name is num_list, the list of new elements to be added is named mynum_list, and the start and end indexes represent the first, last, and one item that needs to be changed.

List Comprehension:

Creating a new list from an existing list is called list comprehension. An existing list can be modified. Using list comprehension, you can change a list by using the following syntax:

Syntax

Code

Output:

 [16, 8] 

Explanation

In the above code, we used num_list = [item * 2 for the item with num_list as item % 2 == 0] to parse the list to create a new list based on the main list of num_list elements. Filters the master list num_list to store only even numbers. This is done by the if item % 2 == 0 condition, which checks whether the remainder of a number divided by 2 is 0. The result of each even number passing through the hole is given 2 rounds. 2 Expressions in the sense of a list. The result of the list realization, a new list of twice even numbers, is then returned to the original num_list.

Conclusion

Python provides several ways to change list elements efficiently. Depending on your requirements, you can target, update, or swap values precisely by utilizing indexing, assignment, slicing, and the replace() method. Keep in mind that edits to lists modify the original object directly. Gaining proficiency in these methods will enable you to work with lists in Python programs more effectively.