org_roam/Notes/20250804214537-python_set.org

python-set

Sets are used to store multiple items in a single variable.

Set is one of 4 built-in data types in Python used to store collections of data, the other 3 are List, Tuple, and Dictionary, all with different qualities and usage.

A set is a collection which is unordered, unchangeable*, and unindexed.

*Note: Set items are unchangeable, but you can remove items and add new items.

Sets are written with curly brackets. Example:

  # Create a Set:
  thisset = {"apple", "banana", "cherry"}
  print(thisset)

Notes:

Sets are fast, Note that empty Set cannot be created through {}, it creates a dictionary, unless you include values. set is implemented as a hash table, so you can expect lookup, insert, delete to be O(1) on average.