What are sets used for in Python?

Sets in Python are used to store unique, unordered elements.

Main applications:

• Removing duplicates: Easily obtain a set of unique elements from a list or tuple.

  # Example of removing duplicates
  my_list = [1, 2, 2, 3, 4, 4, 5]
  unique_elements = set(my_list)
  # unique_elements is now {1, 2, 3, 4, 5}
  

• Membership testing: Very efficient membership check in a set (average complexity O(1)).

  # Example of membership check
  my_set = {1, 2, 3}
  print(5 in my_set)
  # Output: False
  

• Set operations: Union, intersection, difference, symmetric difference.

  Operation	Method/operator	Description	Example ({1, 2}, {2, 3})	Result
  Union	union() / `	`	Elements from both sets	`{1, 2}
  Intersection	intersection() / &	Common elements	{1, 2} & {2, 3}	{2}
  Difference	difference() / -	Elements of first set not in second	{1, 2} - {2, 3}	{1}
  Symmetric difference	symmetric_difference() / ^	Elements not common to both	{1, 2} ^ {2, 3}	{1, 3}

• Fast comparison: Equality, subset, superset.

  # Examples of comparison
  set1 = {1, 2, 3}
  set2 = {1, 2}
  print(set2.issubset(set1)) # Check if set2 is subset of set1
  # Output: True
  

Sets are ideal when element order does not matter, and high performance is needed for membership testing and duplicate removal.