A list is one of the many built-in data structures that allows us to work with a collection of data in sequential order.

We can store the list of top three mountains by height in a list as shown below:

mountains = ["Mauna Kea", "Mt. Everest", "K2"]

Notice that:

• A list begins and ends with square brackets ([ & ]).
• And each item is separated by a comma (,).

We can combine multiple data types in one list. For example, the following list contains both a string and an integer:

mixed_list = ["Hemanta", 12]

Lists can contain any data type in Python! For example, this list contains a string, integer, boolean and float.

mixed_list = ["Hemanta", 12, True, 24.8]

Empty Lists

We can create an empty list as shown below:

empty_list = [ ]

Fill up An Empty List

append()

We can use the popular list method .append() to add an element to the end of a list.

name = ["Hemanta", "Kumar"]

name.append("Sundaray")

print(name)

# ['Hemanta', 'Kumar', 'Sundaray']

List Concatenation

When we want to add multiple items to a list, we can use + to combine two lists.

Note that we can only use + with other lists.

first_name = ["Hemanta"]

last_name = ["Sundaray"]

full_name = first_name + last_name

print(full_name)

# ['Hemanta', 'Sundaray']

Accessing List Elements

We can select a single element from a list by using square brackets ([]) and the index of the list item.

Consider the list below:

energy_drinks = ["Red Bull", "Monster", "Bang"]

If we want to access the third element of the list above, we would use print(energy_drinks[2]).

energy_drinks = ["Red Bull”, “Monster”, “Bang”]

print(energy_drinks[2])

# Bang

Negative Index

We can use the index -1 to select the last item of a list, even when we don’t know how many items are there in the list.

Consider the following list with 5 items:

chocolate = ["Nestle”, “Milka”, “Ghirardelli”, “Cadbury”, “Godiva”]

If we select the -1 index, we get the final element"

print(chocolate[-1])

# Godiva

Modifying List Elements

We can change a value in a list by reassigning the value using the specific index.

Consider the following list:

candies = ["Wrigley”, “Ferrero”, “Mondelez”, “Meizi”, “Hershey”]

We can change the value of the third item (index 2) as shown below:

candies[2] = "Lindt"

print(candies)

# ['Wrigley', 'Ferrero', 'Lindt', 'Meizi', 'Hershey']

Removing Items From a List

We can remove elements in a list using the remove() Python method.

Below, we have a list of the top three car brands in Korea:

brands = ["Hyundai", "Kia", "GM"]

We can remove Kia by using the remove() method:

brands = ["Hyundai", "Kia", "GM"]

brands.remove("Kia")

print(brands)

# ['Hyundai', 'GM']

We can also use .remove() on a list that has duplicate elements:

Only the first instance of the matching element is removed:

brands = ["Hyundai", "Kia", "Kia", "GM"]

brands.remove("Kia")

print(brands)

# ['Hyundai', 'Kia', 'GM']

Two-Dimensional (2D) Lists

Lists can contain other lists! We will commonly refer to these as two-dimensional lists.

country_capital = [["India", "New Delhi"], ["China", "Beijing"], ["South Korea", "Seoul"], ["Japan", "Tokyo"]]

Accessing 2-D Lists

Two-dimensional lists can be accessed similar to their one-dimensional counterparts. Instead of providing a single pair of brackets, we will use an additional set for each dimension past the first.

If we wanted to access China’s capital:

# Access the sublist at index 1, and then access the 1st index of that sublist.

china_capital = country_capital[1][1]

print(china_capital)

# Beijing

Modifying 2D Lists

The following list stores the floor numbers of different clothing lines:

floor_line = [["First", "Menswear"], ["Second", "Womenswear"], ["Third", "Kidswear"]]

To change a value in a two-dimensional list, reassign the value using the specific index.

floor_line[0][1] = "Accessories"

print(floor_line)

# [['First', 'Accessories'], ['Second', 'Womenswear'], ['Third', 'Kidswear']]