Python Built-in Data Structures: Lists, Sets, Dictionaries, and Tuples

Lists are ordered, mutable collections that allow duplicate elements. They are suitable when element order matters and the collection needs to be modified, such as storing a sequence of numbers or names.

list = [1, 2, 3, 4, 5]  # create a list

list.append(6)  # add an element

print(list)  # output the list

Sets are unordered, mutable collections that automatically enforce uniqueness, making them ideal for deduplication and set operations like union, intersection, and difference.

set = {1, 2, 2}  # duplicate values are removed

set.add(4)  # add an element

print(set)  # output: {1, 2, 4}

Dictionaries store key‑value pairs; they are mutable and, since Python 3.6, preserve insertion order. Keys are unique, enabling fast lookup of values by key, useful for mappings such as user profiles or configuration data.

dict = {"name": "Alice", "age": 25}

dict["age"] = 26  # modify a value

print(dict["age"])  # output: 26

Tuples are ordered, immutable collections that may contain duplicate elements. They are used when a fixed sequence of items should not change, such as coordinates or as keys in dictionaries.

tuple = (1, 2, 3)  # immutable tuple

print(tuple)  # output: (1, 2, 3)