Set Operations

🎭 Python Set Operations: The Magic of Mixing & Matching

Imagine you have two toy boxes. Set operations are like cool tricks to combine, compare, and find special toys between them!

🌟 The Story Begins

Meet Sam and Alex. They each have a box of colored marbles.

• Sam’s box: 🔴 Red, 🔵 Blue, 🟢 Green
• Alex’s box: 🔵 Blue, 🟡 Yellow, 🟢 Green

Today, they’ll learn 6 magical tricks to play with their marble collections!

1️⃣ Set Union: “Let’s Put EVERYTHING Together!”

The Big Idea: Union means all marbles from both boxes — but no duplicates!

Think of it like a big party. Everyone from both boxes comes. But if Blue is in both? He only comes once!

sam = {"red", "blue", "green"}
alex = {"blue", "yellow", "green"}

# Union: ALL unique marbles
all_marbles = sam | alex
# OR use .union()
all_marbles = sam.union(alex)

print(all_marbles)
# {'red', 'blue', 'green', 'yellow'}

🎨 Visual

graph TD
    A["Sam's Box] --> C[🔴 🔵 🟢]
    B[Alex's Box"] --> D["🔵 🟡 🟢"]
    C --> E["UNION"]
    D --> E
    E --> F["🔴 🔵 🟢 🟡"]

Remember: | or .union() = Everyone’s invited!

2️⃣ Set Intersection: “What Do We BOTH Have?”

The Big Idea: Intersection finds marbles that appear in both boxes.

Like finding twins! Only marbles that Sam AND Alex both own.

sam = {"red", "blue", "green"}
alex = {"blue", "yellow", "green"}

# Intersection: SHARED marbles only
shared = sam & alex
# OR use .intersection()
shared = sam.intersection(alex)

print(shared)
# {'blue', 'green'}

🎨 Visual

graph TD
    A["Sam: 🔴 🔵 🟢"] --> C["Find Twins"]
    B["Alex: 🔵 🟡 🟢"] --> C
    C --> D["🔵 🟢"]
    D --> E["Only these are in BOTH!"]

Remember: & or .intersection() = Only the matching ones!

3️⃣ Set Difference: “What’s ONLY in MY Box?”

The Big Idea: Difference shows what’s special to one box — not in the other.

Sam wants to know: “Which marbles do I have that Alex doesn’t?”

sam = {"red", "blue", "green"}
alex = {"blue", "yellow", "green"}

# Sam's unique marbles (not in Alex's box)
only_sam = sam - alex
# OR use .difference()
only_sam = sam.difference(alex)

print(only_sam)
# {'red'}

# Alex's unique marbles
only_alex = alex - sam
print(only_alex)
# {'yellow'}

🎨 Visual

graph TD
    A["Sam: 🔴 🔵 🟢"]
    B["Alex: 🔵 🟡 🟢"]
    A --> C["Sam - Alex"]
    C --> D["🔴 Only Sam!"]
    B --> E["Alex - Sam"]
    E --> F["🟡 Only Alex!"]

Remember: - or .difference() = Mine but not yours!

4️⃣ Symmetric Difference: “What’s NOT Shared?”

The Big Idea: Find everything that’s in ONE box but NOT in BOTH.

It’s like saying: “Show me all the special, non-matching marbles!”

sam = {"red", "blue", "green"}
alex = {"blue", "yellow", "green"}

# Marbles in ONE box only (not shared)
unique_to_either = sam ^ alex
# OR use .symmetric_difference()
unique_to_either = sam.symmetric_difference(alex)

print(unique_to_either)
# {'red', 'yellow'}

🎨 Visual

graph TD
    A["Sam: 🔴 🔵 🟢"]
    B["Alex: 🔵 🟡 🟢"]
    A --> C["Symmetric Diff"]
    B --> C
    C --> D["🔴 🟡"]
    D --> E["Unique to ONE box only"]

Remember: ^ or .symmetric_difference() = The oddballs!

5️⃣ Set Comparison Methods: “Who Has More?”

Sets can be compared like people comparing their collections!

🔹 Subset: “Does Alex have everything Sam has?”

small = {"blue", "green"}
big = {"red", "blue", "green", "yellow"}

# Is small inside big?
print(small.issubset(big))  # True
print(small <= big)          # True

# Is small a PROPER subset? (smaller, not equal)
print(small < big)           # True

🔹 Superset: “Does Sam contain Alex’s entire collection?”

big = {"red", "blue", "green", "yellow"}
small = {"blue", "green"}

# Does big contain all of small?
print(big.issuperset(small))  # True
print(big >= small)            # True

# Proper superset (strictly bigger)
print(big > small)             # True

🔹 Disjoint: “Zero Matches!”

cats = {"whiskers", "mittens"}
dogs = {"buddy", "max"}

# Do they share anything?
print(cats.isdisjoint(dogs))  # True (nothing shared!)

foods = {"pizza", "tacos"}
favorites = {"pizza", "ice cream"}
print(foods.isdisjoint(favorites))  # False (pizza!)

📋 Quick Comparison Chart

6️⃣ Set Comprehensions: “Build Sets Like a Pro!”

The Big Idea: Create sets with a magic one-liner!

Just like a factory that picks and transforms items automatically.

🔹 Basic Set Comprehension

# Squares of numbers 1 to 5
squares = {x**2 for x in range(1, 6)}
print(squares)
# {1, 4, 9, 16, 25}

🔹 With a Condition (Filter)

# Only even squares
even_squares = {x**2 for x in range(1, 11) if x % 2 == 0}
print(even_squares)
# {4, 16, 36, 64, 100}

🔹 Transform Strings

words = ["Hello", "WORLD", "Python"]
# Get unique first letters (lowercase)
first_letters = {word[0].lower() for word in words}
print(first_letters)
# {'h', 'w', 'p'}

🔹 From Another Collection

numbers = [1, 2, 2, 3, 3, 3, 4]
# Unique doubled values
doubled = {n * 2 for n in numbers}
print(doubled)
# {2, 4, 6, 8}

🎨 Comprehension Formula

graph LR
    A["{expression}"] --> B["for item in collection"]
    B --> C["if condition"]
    C --> D["= NEW SET!"]

Pattern: {expression for item in collection if condition}

🏆 Summary: Your 6 Magic Tricks!

Set Comprehension Template

{expression for item in collection if condition}

🚀 You Did It!

You now know how to:

• Combine sets with Union
• Find twins with Intersection
• Spot differences with Difference
• Find oddballs with Symmetric Difference
• Compare sizes with Comparison Methods
• Build sets fast with Comprehensions

These tricks work with any collection — names, numbers, even pizza toppings! 🍕

Go experiment. Mix. Match. Create!