Python Set Methods
Master set methods for working with unique collections
🎯 Understanding Sets
Sets store unique items with no duplicates. Perfect for removing duplicates and mathematical operations.
# Basic set creation
colors = {"red", "blue", "green"}
numbers = {1, 2, 3, 3, 2} # Duplicates removed
print(numbers) # {1, 2, 3}
Set Methods Overview
Sets have many useful methods for managing unique collections:
Adding Items
Add single or multiple items
Removing Items
Remove items safely or forcefully
Set Operations
Mathematical set operations
Utility Methods
Clear, copy, and check sets
🔹 Adding Items
Add single items or multiple items to sets
# add() - Add one item
fruits = {"apple", "banana"}
fruits.add("cherry")
print(fruits) # {'apple', 'banana', 'cherry'}
# update() - Add multiple items
fruits.update(["orange", "grape"])
print(fruits) # {'apple', 'banana', 'cherry', 'orange', 'grape'}
# Add from another set
more_fruits = {"kiwi", "mango"}
fruits.update(more_fruits)
print(fruits)
🔹 Removing Items
Different ways to remove items from sets
# remove() - Removes item (error if not found)
colors = {"red", "blue", "green"}
colors.remove("blue")
print(colors) # {'red', 'green'}
# discard() - Removes item (no error if not found)
colors.discard("yellow") # No error
colors.discard("red")
print(colors) # {'green'}
# pop() - Removes random item
numbers = {1, 2, 3, 4, 5}
removed = numbers.pop()
print(f"Removed: {removed}")
print(numbers)
# clear() - Remove all items
numbers.clear()
print(numbers) # set()
🔹 Set Operations
Mathematical operations between sets
# union() - Combine sets
set1 = {1, 2, 3}
set2 = {3, 4, 5}
combined = set1.union(set2)
print(combined) # {1, 2, 3, 4, 5}
# intersection() - Common items
common = set1.intersection(set2)
print(common) # {3}
# difference() - Items in first but not second
diff = set1.difference(set2)
print(diff) # {1, 2}
# symmetric_difference() - Items in either but not both
sym_diff = set1.symmetric_difference(set2)
print(sym_diff) # {1, 2, 4, 5}
🔹 Checking Sets
Check relationships between sets
# issubset() - Check if all items are in another set
small = {1, 2}
big = {1, 2, 3, 4}
print(small.issubset(big)) # True
# issuperset() - Check if contains all items of another
print(big.issuperset(small)) # True
# isdisjoint() - Check if no common items
set_a = {1, 2, 3}
set_b = {4, 5, 6}
print(set_a.isdisjoint(set_b)) # True
# Check membership
print(2 in set_a) # True
print(7 in set_a) # False
🔹 Practical Examples
Real-world uses of set methods
# Remove duplicates from list
numbers = [1, 2, 2, 3, 3, 4]
unique = list(set(numbers))
print(unique) # [1, 2, 3, 4]
# Find common interests
alice_hobbies = {"reading", "swimming", "coding"}
bob_hobbies = {"swimming", "gaming", "coding"}
common = alice_hobbies.intersection(bob_hobbies)
print(common) # {'swimming', 'coding'}
# Track unique visitors
visitors = set()
visitors.add("user123")
visitors.add("user456")
visitors.add("user123") # Duplicate ignored
print(len(visitors)) # 2