Lesson 9: Lists, Tuples, and Sets

🎯 Lesson Objective

To understand how to work with Python’s most common collection data types — Lists, Tuples, and Sets, and how to manipulate and use them effectively.

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🧩 1. Lists

A list is a mutable (changeable) collection of items, written with square brackets [ ].

✅ Example:

fruits = ["apple", "banana", "cherry"]
print(fruits)

Output:

['apple', 'banana', 'cherry']

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⚙️ List Operations

Operation	Example	Output
Access element	fruits[0]	apple
Negative index	fruits[-1]	cherry
Slice	fruits[0:2]	['apple', 'banana']
Length	len(fruits)	3
Add item	fruits.append('orange')	['apple', 'banana', 'cherry', 'orange']
Insert item	fruits.insert(1, 'mango')	['apple', 'mango', 'banana', 'cherry']
Remove item	fruits.remove('banana')	['apple', 'cherry']
Pop item	fruits.pop()	removes last element
Reverse	fruits.reverse()	reversed list
Sort	fruits.sort()	alphabetically sorted

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🔁 Looping Through a List

numbers = [10, 20, 30, 40]
for num in numbers:
    print(num)

Output:

10
20
30
40

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🧮 List Comprehension

A short way to create lists.

squares = [x**2 for x in range(5)]
print(squares)

Output:

[0, 1, 4, 9, 16]

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🧱 2. Tuples

A tuple is an immutable (unchangeable) sequence, written with parentheses ( ).

✅ Example:

colors = ("red", "green", "blue")
print(colors)

Output:

('red', 'green', 'blue')

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⚙️ Tuple Operations

Operation	Example	Output
Access	colors[1]	green
Length	len(colors)	3
Count	colors.count('red')	1
Index	colors.index('blue')	2

Note: You cannot modify a tuple (no append/remove/sort).

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🔁 Looping Through a Tuple

for color in colors:
    print(color)

Output:

red
green
blue

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🔄 Tuple Unpacking

person = ("Sameer", 25, "Warangal")
name, age, city = person
print(name)
print(age)
print(city)

Output:

Sameer
25
Warangal

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🔷 3. Sets

A set is an unordered, unique collection written with curly braces { }.

✅ Example:

fruits = {"apple", "banana", "cherry", "apple"}
print(fruits)

Output:

{'apple', 'banana', 'cherry'}   # Duplicates removed

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⚙️ Set Operations

Operation	Example	Output
Add item	fruits.add('orange')	adds one item
Update	fruits.update(['mango','grape'])	adds multiple items
Remove	fruits.remove('banana')	removes banana
Discard	fruits.discard('kiwi')	no error if missing
Clear	fruits.clear()	empty set

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🔢 Set Mathematical Operations

Sets are useful for union, intersection, and difference.

a = {1, 2, 3, 4}
b = {3, 4, 5, 6}

print(a.union(b))         # {1, 2, 3, 4, 5, 6}
print(a.intersection(b))  # {3, 4}
print(a.difference(b))    # {1, 2}

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🔁 Looping Through a Set

for item in {"cat", "dog", "bird"}:
    print(item)

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🧠 4. Key Differences

Feature	List	Tuple	Set
Syntax	[ ]	( )	{ }
Mutable	✅ Yes	❌ No	✅ Yes
Ordered	✅ Yes	✅ Yes	❌ No
Allows Duplicates	✅ Yes	✅ Yes	❌ No
Indexed	✅ Yes	✅ Yes	❌ No

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🌍 5. Real-Life Example – Student Grades

students = ["Ali", "Sara", "John"]
grades = (85, 90, 78)
subjects = {"Math", "Science", "English"}

print("Students:", students)
print("Grades:", grades)
print("Subjects:", subjects)

Output:

Students: ['Ali', 'Sara', 'John']
Grades: (85, 90, 78)
Subjects: {'Math', 'Science', 'English'}

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