Lists – Creation and Indexing

In Python, a list is a collection of items that are ordered and changeable. Lists are one of the most common data structures used in data analysis.

You can store anything in a list — numbers, strings, or even other lists.

To create a list, use square brackets [] and separate the items with commas:

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

This list has 3 items. Lists can grow or shrink dynamically, and you can update them anytime.

Python lists are zero-indexed. This means:

• The first item is at index 0
• The second item is at index 1
• And so on...

You can also use negative indexing to access items from the end:

• -1 refers to the last item
• -2 refers to the second-to-last item

Let’s look at some real examples in the code block below.

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# Creating a list of cities
cities = ["New York", "Chicago", "Los Angeles", "Houston"]

# Accessing the first item
print("First city:", cities[0])  # New York

# Accessing the third item
print("Third city:", cities[2])  # Los Angeles

# Accessing the last item using negative index
print("Last city:", cities[-1])  # Houston

# Accessing the second-to-last item
print("Second-to-last city:", cities[-2])  # Los Angeles

Lists allow you to store and organize data in a flexible way. Indexing is essential when retrieving specific values for analysis, filtering, or looping through data.

You’ll use lists a lot when analyzing data in Python — get comfortable with them early!

In the next lesson, you’ll learn how to modify and slice lists, letting you extract groups of values or change parts of the list easily.