Tuples and Sets

# Tuples and Sets

Welcome to Chapter 11! After mastering lists, let's explore two more essential data structures: tuples (immutable sequences) and sets (unique, unordered collections).

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1. Learning Objectives #

• Create and use tuples and their methods.

• Understand immutability and when to use tuples vs lists.

• Create sets and perform set operations.

• Use frozensets for immutable sets.

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2. Tuples #

Creating Tuples #

```python id="py11ex1" # Creating tuples colors = ("red", "green", "blue") single = (42,) # Single element tuple needs comma! noparens = 1, 2, 3 # Parentheses are optional empty = () from_list = tuple([1, 2, 3])

print(colors) # ('red', 'green', 'blue') print(type(colors)) # <class 'tuple'>

### Tuple Operations

python id="py11_ex2" coords = (10, 20, 30, 40, 50)

# Indexing and slicing (same as lists) print(coords[0]) # 10 print(coords[-1]) # 50 print(coords[1:3]) # (20, 30)

# Methods (only 2!) print(coords.count(20)) # 1 print(coords.index(30)) # 2

# Length, min, max, sum print(len(coords)) # 5 print(sum(coords)) # 150

# Tuple unpacking x, y, z = (1, 2, 3) print(f"x={x}, y={y}, z={z}")

# Extended unpacking first, *rest = (1, 2, 3, 4, 5) print(first) # 1 print(rest) # [2, 3, 4, 5]

# Tuples are IMMUTABLE # coords[0] = 99 # ❌ TypeError!

### Why Use Tuples?

python id="py11ex3" # 1. As dictionary keys (lists can't be keys) locations = {(40.7, -74.0): "New York", (51.5, -0.1): "London"}

# 2. Function return values def getuser(): return "Alice", 25, "alice@email.com"

name, age, email = get_user() print(f"{name}, {age}, {email}")

# 3. Data integrity — prevent accidental modification DAYS = ("Mon", "Tue", "Wed", "Thu", "Fri", "Sat", "Sun")

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## 3. Sets

### Creating Sets

python id="py11ex4" # Creating sets — unordered, unique elements fruits = {"apple", "banana", "cherry"} numbers = {1, 2, 3, 2, 1} # Duplicates removed! print(numbers) # {1, 2, 3}

# From list (removes duplicates) names = ["Alice", "Bob", "Alice", "Charlie", "Bob"] uniquenames = set(names) print(uniquenames) # {'Alice', 'Bob', 'Charlie'}

# Empty set (NOT {}, that's a dict!) emptyset = set()

### Set Methods

python id="py11_ex5" colors = {"red", "green", "blue"}

# Adding colors.add("yellow") colors.update(["purple", "orange"]) print(colors)

# Removing colors.remove("red") # Raises KeyError if not found colors.discard("pink") # No error if not found popped = colors.pop() # Remove random element

# Membership (very fast — O(1)) print("blue" in colors) # True

### Set Operations

python id="py11_ex6" a = {1, 2, 3, 4, 5} b = {4, 5, 6, 7, 8}

# Union (all elements) print(a | b) # {1, 2, 3, 4, 5, 6, 7, 8} print(a.union(b))

# Intersection (common elements) print(a & b) # {4, 5} print(a.intersection(b))

# Difference (in a but not b) print(a - b) # {1, 2, 3} print(a.difference(b))

# Symmetric difference (in a or b but not both) print(a ^ b) # {1, 2, 3, 6, 7, 8}

# Subset and superset print({1, 2}.issubset(a)) # True print(a.issuperset({1, 2})) # True

Set Operations Visualization: A = {1,2,3,4,5} B = {4,5,6,7,8}

Union (A | B): {1,2,3,4,5,6,7,8} Intersection (A & B): {4,5} Difference (A - B): {1,2,3} Sym. Diff (A ^ B): {1,2,3,6,7,8}

### Set Comprehension

python id="py11_ex7" squares = {x**2 for x in range(10)} print(squares) # {0, 1, 4, 9, 16, 25, 36, 49, 64, 81}

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## 4. Frozenset (Immutable Set)

python id="py11ex8" fs = frozenset([1, 2, 3]) # fs.add(4) # ❌ AttributeError!

# Can be used as dictionary key or set element setsof_sets = {frozenset([1, 2]), frozenset([3, 4])}

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## 5. Comparison: List vs Tuple vs Set

| Feature | List | Tuple | Set |
|---------|------|-------|-----|
| Syntax | `[1,2,3]` | `(1,2,3)` | `{1,2,3}` |
| Mutable | Yes | No | Yes |
| Ordered | Yes | Yes | No |
| Duplicates | Allowed | Allowed | Not allowed |
| Indexing | Yes | Yes | No |
| Use Case | General collection | Fixed data | Unique items |

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## 6. Practical Examples

### Remove Duplicates Preserving Order

python id="py11_ex9" items = [3, 1, 4, 1, 5, 9, 2, 6, 5, 3] unique = list(dict.fromkeys(items)) print(unique) # [3, 1, 4, 5, 9, 2, 6]

### Find Common Elements

python id="py11_ex10" list1 = [1, 2, 3, 4, 5] list2 = [4, 5, 6, 7, 8] common = list(set(list1) & set(list2)) print(f"Common: {common}") # [4, 5] ``

Q2: Empty set is created by: A) {} B) set() C) () D) [] Answer: B — {} creates an empty dict.

Q3: {1,2,3} & {2,3,4} returns: A) {1,2,3,4} B) {2,3} C) {1,4} D) Error Answer: B — Intersection.

Q5: (42,) is a: A) Integer B) Tuple C) List D) Set Answer: B — The comma makes it a tuple.

Q6: Single-element tuple without comma: A) (42) is a tuple B) (42) is an integer C) Error D) None Answer: B

Q8: frozenset is: A) Mutable set B) Immutable set C) Frozen list D) Constant Answer: B

Q10: set([1,1,2,2,3]) returns: A) [1,2,3] B) {1,2,3} C) (1,2,3) D) Error Answer: B

1. 3. How to remove duplicates from a list? list(set(data)) or list(dict.fromkeys(data)) for order.

1. 4. Can you have a set of sets? Not directly. Use frozenset elements.

1. 5. What is tuple packing and unpacking? Packing: t = 1, 2, 3. Unpacking: a, b, c = t.

• Set operations: union (|), intersection (&), difference (-), symmetric difference (^`).

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10. Next Chapter Recommendation #

In Chapter 12: Dictionaries in Python, you'll master key-value pairs, the most powerful data structure for real-world programming! 🚀