What is a Set?
A set in Python is an unordered collection of unique items. Think of it as a bag of marbles —you can have different colors, but no duplicates!
Why Use Sets?
- No duplicates allowed
- Super fast lookups
- Mathematical set operations (union, intersection, etc.)
Creating a Set
Sets are created using curly brackets {} or the set() function.
fruits = {"apple", "banana", "cherry", "apple"} # Duplicate 'apple' is ignored
print(fruits) # Outputs: {'banana', 'apple', 'cherry'}
Empty Set?
To create an empty set, use set(), NOT {}.
empty_set = set() # Correct
empty_dict = {} # This is a dictionary Adding and Removing Items
Add an item:
fruits.add("mango")
print(fruits)
Remove an item:
fruits.remove("banana") # Error if not found
fruits.discard("cherry") # No error if not found
print(fruits)
Set Operations
Union (Combine two sets):
a = {1, 2, 3}
b = {3, 4, 5}
print(a | b) # Outputs: {1, 2, 3, 4, 5}
Intersection (Common elements):
print(a & b) # Outputs: {3}
Difference (Items in A but not in B):
print(a - b) # Outputs: {1, 2}
Looping Through a Set
for fruit in fruits:
print(fruit)
Summary
| Concept | Description |
|---|---|
| Set | Unordered collection of unique items |
| Mutable | Can add or remove elements |
| No Duplicates | Automatically removes duplicates |
| Operations | .add(), .remove(), .discard(), union (` |
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