Python Data Structures

Last updated: September 22, 2024

• lists - mutable ordered collection
• tuples - immutable ordered collection
• sets - mutable unordered collection of unique elements

Lists

Mutable, ordered collection of elements - can store elements of different data types, including integers, strings, and even other lists.

Creating a List

fruits = ['apple', 'banana', 'cherry']
numbers = [1, 2, 3, 4, 5]
mixed_list = ['apple', 1, 'banana', 2]

List Methods and Operations

fruits = ['apple', 'banana', 'cherry']
print(fruits[1])  # Output: banana

Adding elements - the append() method:

fruits = ['apple', 'banana', 'cherry']
fruits.append('orange')
print(fruits)  # Output: ['apple', 'banana', 'cherry', 'orange']

Removing elements - the remove() method:

fruits = ['apple', 'banana', 'cherry']
fruits.remove('banana')
print(fruits)  # Output: ['apple', 'cherry']

Slicing - extract a portion of a list:

numbers = [1, 2, 3, 4, 5]
sliced_numbers = numbers[1:4]
print(sliced_numbers)  # Output: [2, 3, 4]

Tuples

Immutable, ordered collection of elements - once created, its contents cannot be modifed.

Creating a Tuple

fruits = ('apple', 'banana', 'cherry')
coordinates = (3, 4, 5)

Tuple Methods and Operations

fruits = ('apple', 'banana', 'cherry')
print(fruits[1])  # Output: banana

Counting elements - the count() method:

numbers = (1, 2, 3, 2, 4, 2)
count_of_twos = numbers.count(2)
print(count_of_twos)  # Output: 3

Finding the index - the index() method:

fruits = ('apple', 'banana', 'cherry')
index_of_banana = fruits.index('banana')
print(index_of_banana)  # Output: 1

Sets

Unordered, mutable collection of unique elements - duplicate elements are not allowed.

Creating a Set

fruits = {'apple', 'banana', 'cherry'}
numbers = set([1, 2, 3, 4, 5])

Set Methods and Operations

Adding elements - the add() method:

fruits = {'apple', 'banana', 'cherry'}
fruits.add('orange')
print(fruits)  # Output: {'apple', 'banana', 'cherry', 'orange'}

Removing elements - the remove() method:

fruits = {'apple', 'banana', 'cherry'}
fruits.remove('banana')
print(fruits)  # Output: {'apple', 'cherry'}

set1 = {1, 2, 3}
set2 = {3, 4, 5}
union_set = set1.union(set2)
# or
union_set = set1 | set2
print(union_set)  # Output: {1, 2, 3, 4, 5}

Intersection - the intersection() method or the & operator:

set1 = {1, 2, 3}
set2 = {3, 4, 5}
intersection_set = set1.intersection(set2)
# or
intersection_set = set1 & set2
print(intersection_set)  # Output: {3}

Difference - the difference() method or the - operator:

set1 = {1, 2, 3}
set2 = {3, 4, 5}
difference_set = set1.difference(set2)
# or
difference_set = set1 - set2
print(difference_set)  # Output: {1, 2}