Lists: Ordered, Mutable Sequences

Lists are the most versatile and commonly used data structure in Python. A list is an ordered collection of items, and it is mutable (meaning you can change its contents after creation).

Lists are defined using square brackets [], with items separated by commas.

Creating Lists

Lists can hold items of different data types (though often they hold items of the same type).

python

List of strings

fruits = ['apple', 'banana', 'cherry']

List of mixed types

mixed_list = [1, 'hello', 3.14, True]

Empty list

empty_list = []

Accessing List Elements

Lists use zero-based indexing and slicing, just like strings.

python print(fruits[0]) # Output: apple print(fruits[-1]) # Output: cherry

Slicing

subset = fruits[1:3] print(subset) # Output: ['banana', 'cherry']

Mutability: Changing Elements

Because lists are mutable, you can change individual elements using their index.

python colors = ['red', 'blue', 'green'] colors[1] = 'yellow' # Change the item at index 1 print(colors) # Output: ['red', 'yellow', 'green']