What is the difference between mutable and immutable data structures?

Data structures that can be modified after creation are called mutable, while those that cannot be changed are called immutable.

Mutable structures allow changing their contents without creating a new object. For example, lists (list) in Python can be modified — adding, removing, or changing elements.

my_list = [1, 2, 3]
my_list.append(4)  # Now my_list = [1, 2, 3, 4]

Immutable structures cannot be changed after creation. For example, tuples (tuple) or strings (str) in Python. If a change is needed, a new object is created.

my_tuple = (1, 2, 3)
# my_tuple[0] = 10  # Error
new_tuple = (10,) + my_tuple[1:]  # Creating a new tuple

Immutability is useful for data security, preventing side effects, and simplifying debugging. Mutable structures are convenient for dynamic data that requires frequent updates.