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Practice

Lists in Python

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

A list can store many kinds of data such as numbers, strings, or even other lists.


Creating a List​

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

Creating a List
fruits = ["apple", "banana", "cherry"]

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


Accessing List Items​

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.


Code Examples​

Here are some examples of how to access list items:

Accessing List Items
# 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

Why Lists Are Important​

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.

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