🐍 Python Deep Dive: Sets & Dictionaries

Deep Dive into Python Sets

Beginner Friendly

🎯 What is a Set?

Hey there! Think of a Set like a magical bag that only keeps unique items! No duplicates allowed! 🎒✨

📚 Key Facts About Sets:

Sets store unique elements only - no duplicates!
Sets are unordered - items have no specific position
Sets are mutable - you can add or remove items
Sets use curly braces {} or the set() function

🐍 Python Code

# Creating a set
my_fruits = {"apple", "banana", "cherry"}
print(my_fruits)  # Output: {'apple', 'banana', 'cherry'}

# Sets remove duplicates automatically!
numbers = {1, 2, 2, 3, 3, 3}
print(numbers)  # Output: {1, 2, 3} - duplicates are gone!

💡

Fun Fact: Sets in Python work just like sets in math class! They're perfect for finding unique items in a collection.

🛠️ Creating Sets

Method 1: Using Curly Braces

# Direct creation
colors = {"red", "green", "blue"}

Method 2: Using set() Function

# From a list
my_list = [1, 2, 3, 3]
my_set = set(my_list)  # {1, 2, 3}

Method 3: Empty Set

# Must use set() for empty set
empty_set = set()
# NOT {} - that creates an empty dictionary!

⚠️ Common Mistake!

# This creates a DICTIONARY, not a set!
wrong = {}  # Empty dictionary
right = set()  # Empty set

⚡ Set Operations

Add Element

fruits = {"apple", "banana"}
fruits.add("cherry")
# {"apple", "banana", "cherry"}

Remove Element

fruits.remove("banana")
# {"apple", "cherry"}
# Or use discard() - no error if not found
fruits.discard("mango")

Union (All items)

set1 = {1, 2, 3}
set2 = {3, 4, 5}
union = set1 | set2  # or set1.union(set2)
# {1, 2, 3, 4, 5}

Intersection (Common items)

set1 = {1, 2, 3}
set2 = {3, 4, 5}
common = set1 & set2  # or set1.intersection(set2)
# {3}

Difference

set1 = {1, 2, 3}
set2 = {3, 4, 5}
diff = set1 - set2  # or set1.difference(set2)
# {1, 2}

🎨 Interactive Venn Diagram

Set A

1, 2, 3

Set B

3, 4, 5

Result: {1, 2, 3, 4, 5}

🧰 Useful Set Methods

Method	Description	Example
`add()`	Adds an element	`s.add(4)`
`remove()`	Removes element (error if not found)	`s.remove(2)`
`discard()`	Removes element (no error if not found)	`s.discard(2)`
`pop()`	Removes and returns random element	`item = s.pop()`
`clear()`	Removes all elements	`s.clear()`
`len()`	Returns number of elements	`len(s)`
`in`	Check if element exists	`3 in s`

Practice Time: Sets Exercises

Exercise 1 Easy +15 points

Create a set called my_set containing the numbers 1, 2, 3, 4, 5. What do you write?

Exercise 2 Medium +20 points

What will be the output of this code?

numbers = {1, 2, 2, 3, 3, 3, 4}
print(len(numbers))

7 4 3 Error

Exercise 3 Medium +20 points

Given set1 = {1, 2, 3} and set2 = {2, 3, 4}, what is the intersection?

{1, 2, 3, 4} {2, 3} {1} {4}

Exercise 4 Challenge +30 points

Match the set operation with its result for sets A = {1, 2, 3} and B = {3, 4, 5}

A | B (Union)

A & B (Intersection)

A - B (Difference)

{3}

{1, 2}

{1, 2, 3, 4, 5}

Exercise 5 Challenge +25 points

Complete the code to find all unique characters in "hello world":

text = "hello world"
unique_chars = 
print(unique_chars)

Sets Mini Quiz

Test your knowledge! Complete this quiz to earn the Sets Master Badge! 🏆

Question 1 of 5

Deep Dive into Python Dictionaries

Intermediate Level

📖 What is a Dictionary?

Think of a Dictionary like a real dictionary! 📚 You look up a word (key) to find its meaning (value)!

📚 Key Facts About Dictionaries:

Dictionaries store key-value pairs
Keys must be unique and immutable (strings, numbers, tuples)
Values can be any data type
Use curly braces {} with key:value format
Dictionaries are ordered (Python 3.7+)

🎨 Visual Representation

"name"

→

"Alice"

"age"

→

"grade"

→

"7th"

🐍 Python Code

# Creating a dictionary
student = {
    "name": "Alice",
    "age": 12,
    "grade": "7th"
}

# Accessing values
print(student["name"])  # Output: Alice
print(student["age"])   # Output: 12

🌟

Did you know? Dictionaries in Python are incredibly fast at looking up values! They use something called "hash tables" behind the scenes.

🛠️ Creating Dictionaries

Method 1: Curly Braces

# Direct creation
person = {"name": "Bob", "age": 25}

Method 2: dict() Constructor

# Using dict()
person = dict(name="Bob", age=25)

Method 3: From Lists

# From two lists
keys = ["a", "b", "c"]
values = [1, 2, 3]
my_dict = dict(zip(keys, values))

Method 4: Empty Dictionary

# Empty dictionary
empty_dict = {}
# OR
empty_dict = dict()

🔑 Accessing and Modifying Values

Access Value

student = {"name": "Alice", "age": 12}

# Method 1: Square brackets
print(student["name"])  # Alice

# Method 2: get() - safer!
print(student.get("name"))  # Alice
print(student.get("grade", "N/A"))  # N/A (default)

Add/Update Value

student = {"name": "Alice"}

# Add new key-value pair
student["age"] = 12

# Update existing value
student["name"] = "Bob"

print(student)  # {'name': 'Bob', 'age': 12}

Delete Elements

student = {"name": "Alice", "age": 12, "grade": "A"}

# Using del
del student["grade"]

# Using pop() - returns the value
age = student.pop("age")  # age = 12

print(student)  # {'name': 'Alice'}

🎮 Try It Yourself: Build a Dictionary!

my_dict = {}

🧰 Dictionary Methods

Method	Description	Example
`keys()`	Returns all keys	`d.keys()`
`values()`	Returns all values	`d.values()`
`items()`	Returns key-value pairs as tuples	`d.items()`
`get(key)`	Returns value (None if not found)	`d.get("name")`
`pop(key)`	Removes and returns value	`d.pop("age")`
`update()`	Updates with another dict	`d.update({"x": 1})`
`clear()`	Removes all items	`d.clear()`

🐍 Looping Through Dictionaries

student = {"name": "Alice", "age": 12, "grade": "A"}

# Loop through keys
for key in student.keys():
    print(key)

# Loop through values
for value in student.values():
    print(value)

# Loop through both
for key, value in student.items():
    print(f"{key}: {value}")

🏠 Nested Dictionaries

Dictionaries can contain other dictionaries! It's like having folders inside folders! 📁📁

🐍 Nested Dictionary Example

# A classroom with students
classroom = {
    "student1": {
        "name": "Alice",
        "age": 12,
        "grades": {"math": 95, "science": 88}
    },
    "student2": {
        "name": "Bob",
        "age": 13,
        "grades": {"math": 82, "science": 90}
    }
}

# Accessing nested values
print(classroom["student1"]["name"])  # Alice
print(classroom["student1"]["grades"]["math"])  # 95

🎨 Visual: Nested Dictionary Structure

classroom

"student1"

"name": "Alice"

"age": 12

"grades"

"math": 95

"science": 88

Practice Time: Dictionary Exercises

Exercise 1 Easy +15 points

Create a dictionary called pet with keys "name" and "species", with values "Buddy" and "dog":

Exercise 2 Easy +15 points

What will this code print?

info = {"city": "Paris", "country": "France"}
print(info["city"])

city Paris France Error

Exercise 3 Medium +20 points

How do you safely get a value that might not exist?

data = {"x": 10}
# Get value for key "y" with default 0 if not found

Exercise 4 Medium +20 points

Arrange the code in correct order to create a dictionary and add a new key:

print(student)

student = {"name": "Alice"}

student["age"] = 12

Exercise 5 Challenge +30 points

Given this nested dictionary, what code accesses Bob's science grade?

school = {
    "class1": {
        "Alice": {"math": 95, "science": 88},
        "Bob": {"math": 82, "science": 90}
    }
}

Dictionaries Mini Quiz

Complete this quiz to earn the Dictionary Master Badge! 🏆