Python Lists: Create, Access, Change and Loop (Beginner Guide)

A list stores many values in a single variable, in order. A shopping list, the scores in a game, the names of students in a class: whenever you have several of something, a list is usually the first tool to reach for.

Creating a list#

Write the items inside square brackets, separated by commas:

fruits = ["apple", "banana", "cherry"]
scores = [88, 92, 79, 95]
empty = []

print(fruits)
print(len(scores))

['apple', 'banana', 'cherry']
4

len() tells you how many items a list has. A list can hold any type of value, and even a mix, though in practice most lists hold one kind of thing.

Accessing items by index#

Each item has a position number called an index. Python counts from 0, so the first item is at index 0:

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

print(fruits[0])
print(fruits[2])
print(fruits[-1])   # negative indexes count from the end

apple
cherry
cherry

-1 is a handy way to get the last item without knowing the list's length.

Slicing: get part of a list#

A slice returns a new list with a range of items. The syntax is list[start:stop], and the stop index is not included:

numbers = [10, 20, 30, 40, 50, 60]

print(numbers[1:4])   # items at index 1, 2, 3
print(numbers[:3])    # from the start up to index 3
print(numbers[3:])    # from index 3 to the end
print(numbers[::2])   # every second item
print(numbers[::-1])  # reversed copy

[20, 30, 40]
[10, 20, 30]
[40, 50, 60]
[10, 30, 50]
[60, 50, 40, 30, 20, 10]

Changing items#

Lists are mutable, which means you can change them after creating them:

colors = ["red", "green", "blue"]
colors[1] = "yellow"
print(colors)

['red', 'yellow', 'blue']

Adding items#

tasks = ["email"]

tasks.append("meeting")          # add to the end
tasks.insert(0, "coffee")        # add at a position
tasks.extend(["report", "gym"])  # add several items

print(tasks)

['coffee', 'email', 'meeting', 'report', 'gym']

Removing items#

tasks = ["coffee", "email", "meeting", "report", "gym"]

tasks.remove("email")    # remove the first matching value
last = tasks.pop()       # remove and return the last item
first = tasks.pop(0)     # remove and return the item at index 0

print(tasks)
print(last, first)

['meeting', 'report']
gym coffee

Useful list operations#

scores = [88, 92, 79, 95, 92]

print(92 in scores)        # is a value present?
print(scores.count(92))    # how many times?
print(scores.index(79))    # where is it first?
print(min(scores), max(scores), sum(scores))

True
2
2
79 95 446

Sorting#

sort() sorts the list in place (it changes the original). sorted() returns a new sorted list and leaves the original alone:

scores = [88, 92, 79, 95]

ranked = sorted(scores, reverse=True)
print(ranked)
print(scores)

scores.sort()
print(scores)

[95, 92, 88, 79]
[88, 92, 79, 95]
[79, 88, 92, 95]

Looping through a list#

The most common thing to do with a list is to go through it item by item with a for loop:

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

for fruit in fruits:
    print(f"I like {fruit}")

I like apple
I like banana
I like cherry

If you also need the position, use enumerate():

for position, fruit in enumerate(fruits, start=1):
    print(position, fruit)

1 apple
2 banana
3 cherry

Loops are explained fully in the Loops lesson.

Building a new list from an old one#

A common pattern is to start with an empty list and append to it inside a loop:

prices = [100, 250, 80]
with_tax = []

for price in prices:
    with_tax.append(round(price * 1.18, 2))

print(with_tax)

[118.0, 295.0, 94.4]

round(..., 2) keeps two decimal places. Without it, 80 * 1.18 would print as 94.39999999999999 because of how decimals are stored in binary (see Data Types).

Python also has a shorter syntax for this called a list comprehension: with_tax = [round(price * 1.18, 2) for price in prices]. You will meet comprehensions properly later in the course.

Common mistakes#

Practice#

scores = [72, 95, 58, 88, 64, 91]

scores = [72, 95, 58, 88, 64, 91]

print("Highest:", max(scores))
print("Lowest:", min(scores))

average = sum(scores) / len(scores)
print("Average:", round(average, 1))

passed = []
for score in scores:
    if score >= 60:
        passed.append(score)

print("Passed:", passed)

Highest: 95
Lowest: 58
Average: 78.0
Passed: [72, 95, 88, 64, 91]

Key takeaway#