Are Python Lists Mutable?

A comprehensive guide to understanding if Python lists are mutable, including a step-by-step explanation and code examples. …

A comprehensive guide to understanding if Python lists are mutable, including a step-by-step explanation and code examples.

Definition: What Are Immutable and Mutable Objects?

In programming, an immutable object is one that cannot be changed once it’s created. In other words, its state remains the same throughout its lifetime. On the other hand, a mutable object can be modified after its creation.

Step-by-Step Explanation: How Python Lists Are Defined

Python lists are defined as lists in Python syntax using square brackets []. They can store multiple values of any data type (e.g., integers, floats, strings, booleans).

my_list = [1, 2, 3, "hello", True]

Step-by-Step Explanation: Are Python Lists Mutable?

Now that we know what lists are, let’s explore if they’re mutable. A list is an ordered collection of values, which means the order in which elements are stored matters.

To check if a list is mutable, try modifying one of its elements and see if it affects other parts of the list.

my_list = [1, 2, 3]

# Modify an element
my_list[0] = 10

print(my_list)  # Output: [10, 2, 3]

As we’ve just demonstrated, modifying one element doesn’t affect other elements. This indicates that lists are indeed mutable.

Code Explanation: Why Lists Are Mutable

Let’s dive into the reason behind list mutability:

• Lists in Python use dynamic memory allocation.
• When you modify an element within a list, it updates the value stored at that particular index.
• Other elements remain unchanged because their indices haven’t been altered.

Here’s an example of creating multiple lists with different lengths and types of values:

list1 = [4, 5, "world"]
list2 = ["foo", 7]
list3 = []

print(list1)  # Output: [4, 5, 'world']
print(list2)  # Output: ['foo', 7]
print(list3)  # Output: []

Step-by-Step Explanation: List Concatenation

When concatenating lists using the + operator or the extend() method, you’re creating a new list by copying elements from one or more existing lists.

list1 = [1, 2]
list2 = [3, 4]

# Using the + operator for concatenation
new_list = list1 + list2

print(new_list)  # Output: [1, 2, 3, 4]

# Using extend() to concatenate lists in-place
list1.extend([5, 6])

print(list1)  # Output: [1, 2, 5, 6]

In the above example:

• The + operator creates a new list (new_list) by copying elements from both list1 and list2.
• The extend() method modifies list1 in-place by adding elements from another list.

Conclusion

Python lists are indeed mutable. This means you can modify their contents, including individual elements and the entire collection itself. Understanding this property is crucial when working with lists and other data structures in Python.