Learn Python Python Sets

Sets are one of Python’s built-in data types used to store multiple unique values in a single variable. They are unordered, mutable, and unindexed, making them ideal for fast membership testing and removing duplicates.

This topic covers sets from basics to practical usage.

What Is a Set?

A set is a collection that:

Stores unique elements only
Is unordered
Is mutable
Does not allow indexing

Set vs List vs Tuple

Feature	List	Tuple	Set
Ordered	Yes	Yes	No
Allows duplicates	Yes	Yes	No
Mutable	Yes	No	Yes
Indexing	Yes	Yes	No

Creating Sets

Using Curly Braces `{}`

Using `set()` Constructor

Empty Set (Important)

This is NOT a set:

Access Set Items

Sets are unordered, so you cannot access items using indexes.

Check If Item Exists

Add Items to a Set

Add One Item – `add()`

Add Multiple Items – `update()`

Remove Items from a Set

`remove()` – Raises Error if Not Found

`discard()` – No Error if Not Found

`pop()` – Removes Random Item

`clear()` – Remove All Items

Set Length

Join Sets (Set Operations)

Union (`|` or `union()`)

Intersection (`&` or `intersection()`)

Difference (`-` or `difference()`)

Symmetric Difference (`^`)

Set Comprehension

Frozen Set (Immutable Set)

Cannot modify:

Common Mistakes

Expecting Order in Sets

Order may change.

Using Mutable Items in Set

When to Use Sets

Use sets when:

You need unique values
Membership checking is frequent
Order does not matter
Removing duplicates is required