Python Data Structures Explained: Lists, Tuples, Sets and Dictionaries

Python data structures are built-in containers in Python programs that gather values together. There are four types of containers: lists, tuples, sets, and dictionaries, each with its own unique characteristics.

Lists are ordered and changeable collections written inside square brackets. They can be modified after creation by adding, removing, replacing, or sorting items. Lists are ideal for collections that will grow or shrink over time, such as shopping carts, to-do items, and search results.

Tuples are similar to lists but are written with round brackets and cannot be changed once created. They are best suited for fixed groups of values that should stay together, such as coordinates, RGB colors, dates, and database records. Tuples can also be used as dictionary keys because they cannot be edited by accident.

Sets store unique values only, written with curly brackets. Adding the same value multiple times results in it being stored only once. Sets do not guarantee a specific order, but they allow for fast membership checking and efficient operations like union, intersection, and difference between groups.

Dictionaries store pairs of keys and values, with keys labeling the values. They are written with curly brackets and use square brackets to access values by their keys. Dictionaries are perfect for modelling real-world objects, as they allow easy access to values using labels. Keys must be unique and unchangeable types like strings or numbers, while values can be anything.

When deciding which container to use, ask three questions: do the values need labels, must duplicates disappear, or is fast membership checking the main job? If labels are needed, choose a dictionary. If duplicates need to be removed or membership checking is the main job, choose a set. If the group should stay exactly as created and is best suited for ordered collections that will grow or shrink, choose a list.

For everything else, the everyday growing, shrinking, ordered collection, choose a list. Most beginner programs can easily handle lists and dictionaries alone.