Summary  
This chapter explains how to use nested lists in Python to create two-dimensional lists of varying lengths and access their elements through multi-level indexing.

General domain of usage  
Representing and accessing tabular data such as geographic information.

As mentioned in the opening chapter, lists in Python can store various data types, even including other lists. What's unique about Python, compared to many other programming languages, is that these **nested lists can differ in length**. 

Let's dive into an example. Imagine we have data about **countries** and **their respective areas**. Instead of jamming all that information into a single list, it would be more organized to have a **distinct list for each country**.

# Two-dimensional list
countries_2d = [["USA", 9629091], ["Canada", 9984670], ["Germany", 357114]]
print(countries_2d)

As illustrated, every country has its dedicated list nested within the primary list. Now, you might wonder, how do we navigate through such a structure? If we're dealing with a two-dimensional list, its elements are also lists. And, **we can access the inner list's items using indexing**.

Consider a two-dimensional list named `countries_2d` that contains `3` main elements (which are **lists**). Each of these lists has `2` items. 

So, `countries_2d[1]` fetches **the second list in the main list** (*keep in mind, Python indexing begins at* `0`). Moreover, `countries_2d[1][0]` retrieves **the first item within that second list**. 

Check out the example below for clarity.

# Two-dimensional list
countries_2d = [['USA', 9629091], ['Canada', 9984670], ['Germany', 357114]]

# Pull elements
print(countries_2d[1])
print(countries_2d[1][0])

Python is an interpreted high-level general-purpose programming language. Unlike HTML, CSS, and JavaScript, which are primarily used for web development, Python is versatile and can be used in various fields, including software development, data science, and back-end development. In this course, you'll explore the core aspects of Python, and by the end, you'll be crafting your own functions!

Dive into the basics of Python, explore your workspace, and perform simple math operations. Learn how to write readable code using comments and handle both basic and advanced mathematical expressions while displaying your results.

Learn how to store and manage data in Python by working with numbers, text, and variables. Understand how to assign values, follow naming conventions, and explore different data types. Gain hands-on experience with string operations, indexing, slicing, and memory recall techniques to efficiently manipulate text in Python.

Learn how to use comparison and logical operators, work with conditional expressions, and apply membership and type comparisons. Build a strong foundation in writing programs that respond dynamically to different conditions using if/else and if/elif/else structures.

Expand your understanding of data types by learning how to group multiple attributes within a single variable. Explore lists, tuples, and dictionaries to efficiently store and manage structured data, along with essential methods for manipulation and retrieval.

Master the art of writing loops in Python—essential constructs for iterating over lists, tuples, dictionaries, and other data structures. Learn to use while and for loops effectively, explore the range function, and work with nested loops to handle complex iteration patterns.

Explore essential built-in functions in Python and take the next step by creating your own. Learn how to define functions, use conditional logic, modify existing functions, and work with lambda expressions to write efficient, reusable code.

How can you retrieve a value from a dictionary by its key?

What is the difference between a tuple and a list?

How can you access the third element in this list?


What does the `copy()` method do for lists in Python?

Is there a strict limit on how deeply you can nest tuples/lists/dictionaries in Python?

How do you update a value in a dictionary?

How would you change "green" to "yellow"?

Nested Lists in Python

Awesome!

Nested Lists in Python