Python sets are a built-in data type used to store an unordered collection of unique elements. They are ideal for tasks like removing duplicates from data, performing fast membership testing, and executing mathematical set operations.

• Creation: Use curly braces {} for non-empty sets (e.g., my_set = {1, 2, 3}) or the set() constructor for empty sets or conversions from other iterables (e.g., set([1, 2, 2]) → {1, 2}).

• Key Properties:

  • No duplicates: Automatically removes repeated values.

  • Unordered: Elements have no fixed position; order may vary between runs.

  • Unindexed: Cannot access elements by index or key.

  • Mutable: Can add or remove elements after creation.

  • Hashable elements only: Only immutable types (e.g., integers, strings, tuples) can be stored; lists or dictionaries are not allowed.

• Common Operations:

  • Add/Remove: Use add() to add an element, remove() (raises error if missing), or discard() (safe removal).

  • Set Math: Use union(), intersection(), difference(), and symmetric_difference() for mathematical operations.

  • Membership Testing: Use in or not in for O(1) lookup speed, much faster than lists.

• Important Note: Use set() to create an empty set—{} creates an empty dictionary, not a set.

Sets are especially powerful for performance-critical operations involving uniqueness and fast lookups.