Lists and Tuples

List

A list is an ordered, mutable collection.

Creating Lists

# Empty list
empty = []
empty = list()

# List with values
numbers = [1, 2, 3, 4, 5]
names = ["홍길동", "김철수", "이영희"]
mixed = [1, "hello", 3.14, True]

# Nested list
matrix = [
    [1, 2, 3],
    [4, 5, 6],
    [7, 8, 9]
]

# Creating with range
numbers = list(range(1, 6))  # [1, 2, 3, 4, 5]
evens = list(range(0, 11, 2))  # [0, 2, 4, 6, 8, 10]

Indexing and Slicing

fruits = ["사과", "바나나", "체리", "포도", "멜론"]

# Indexing
print(fruits[0])    # 사과
print(fruits[-1])   # 멜론
print(fruits[2])    # 체리

# Slicing
print(fruits[1:4])  # ['바나나', '체리', '포도']
print(fruits[:3])   # ['사과', '바나나', '체리']
print(fruits[2:])   # ['체리', '포도', '멜론']
print(fruits[::2])  # ['사과', '체리', '멜론'] (every 2nd item)
print(fruits[::-1]) # ['멜론', '포도', '체리', '바나나', '사과'] (reversed)

# 2D list
matrix = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]
print(matrix[0])    # [1, 2, 3]
print(matrix[1][2]) # 6

Modifying Lists

fruits = ["사과", "바나나", "체리"]

# Changing element
fruits[1] = "딸기"
print(fruits)  # ['사과', '딸기', '체리']

# Changing slice
numbers = [1, 2, 3, 4, 5]
numbers[1:4] = [20, 30]
print(numbers)  # [1, 20, 30, 5]

# Adding elements
fruits.append("포도")       # add to end
print(fruits)  # ['사과', '딸기', '체리', '포도']

fruits.insert(1, "망고")    # insert at position
print(fruits)  # ['사과', '망고', '딸기', '체리', '포도']

# Extending list
more_fruits = ["멜론", "수박"]
fruits.extend(more_fruits)  # add multiple elements
print(fruits)

# Removing elements
fruits.remove("망고")       # remove by value
print(fruits)

popped = fruits.pop()       # remove and return last element
print(popped)               # 수박

fruits.pop(0)               # remove at position
print(fruits)

del fruits[0]               # delete by index
print(fruits)

fruits.clear()              # clear all
print(fruits)               # []

List Operations

# Concatenation
list1 = [1, 2, 3]
list2 = [4, 5, 6]
combined = list1 + list2
print(combined)  # [1, 2, 3, 4, 5, 6]

# Repetition
repeated = [0] * 5
print(repeated)  # [0, 0, 0, 0, 0]

# Length
print(len([1, 2, 3, 4, 5]))  # 5

# Membership
fruits = ["사과", "바나나", "체리"]
print("사과" in fruits)        # True
print("포도" in fruits)        # False
print("포도" not in fruits)    # True

# Count
numbers = [1, 2, 2, 3, 2, 4]
print(numbers.count(2))       # 3

# Find index
fruits = ["사과", "바나나", "체리", "바나나"]
print(fruits.index("바나나"))  # 1 (first occurrence)

Sorting Lists

numbers = [3, 1, 4, 1, 5, 9, 2]

# sort() - modifies original
numbers.sort()
print(numbers)  # [1, 1, 2, 3, 4, 5, 9]

numbers.sort(reverse=True)
print(numbers)  # [9, 5, 4, 3, 2, 1, 1]

# sorted() - returns new list
numbers = [3, 1, 4, 1, 5, 9, 2]
sorted_numbers = sorted(numbers)
print(sorted_numbers)  # [1, 1, 2, 3, 4, 5, 9]
print(numbers)         # [3, 1, 4, 1, 5, 9, 2] (original preserved)

# Sorting strings
words = ["banana", "apple", "cherry"]
words.sort()
print(words)  # ['apple', 'banana', 'cherry']

# Reverse
numbers.reverse()
print(numbers)

# Sorting with key function
words = ["apple", "pie", "zoo", "a"]
words.sort(key=len)  # by length
print(words)  # ['a', 'pie', 'zoo', 'apple']

# Complex sorting
students = [
    {"name": "홍길동", "score": 85},
    {"name": "김철수", "score": 92},
    {"name": "이영희", "score": 78}
]
students.sort(key=lambda x: x["score"], reverse=True)
print(students)

List Comprehension

# Basic form
squares = [x ** 2 for x in range(1, 6)]
print(squares)  # [1, 4, 9, 16, 25]

# With condition
evens = [x for x in range(1, 11) if x % 2 == 0]
print(evens)  # [2, 4, 6, 8, 10]

# if-else
numbers = [1, 2, 3, 4, 5]
result = ["짝수" if x % 2 == 0 else "홀수" for x in numbers]
print(result)  # ['홀수', '짝수', '홀수', '짝수', '홀수']

# Nested list
matrix = [[i*j for j in range(1, 4)] for i in range(1, 4)]
print(matrix)  # [[1, 2, 3], [2, 4, 6], [3, 6, 9]]

# Flattening
nested = [[1, 2], [3, 4], [5, 6]]
flat = [num for sublist in nested for num in sublist]
print(flat)  # [1, 2, 3, 4, 5, 6]

# Practical example
names = ["홍길동", "김철수", "이영희"]
upper_names = [name.upper() for name in names]
print(upper_names)

# Conditional transformation
scores = [85, 92, 78, 95, 88]
grades = ["Pass" if score >= 80 else "Fail" for score in scores]
print(grades)

Tuple

A tuple is an ordered, immutable collection.

Creating Tuples

# Empty tuple
empty = ()
empty = tuple()

# Tuple with values
numbers = (1, 2, 3, 4, 5)
mixed = (1, "hello", 3.14, True)

# Without parentheses
point = 10, 20
print(point)  # (10, 20)

# Single element tuple (comma required!)
single = (5,)
not_tuple = (5)   # This is just an int
print(type(single))    # <class 'tuple'>
print(type(not_tuple)) # <class 'int'>

# Converting from list
numbers_list = [1, 2, 3]
numbers_tuple = tuple(numbers_list)
print(numbers_tuple)  # (1, 2, 3)

Accessing Tuples

colors = ("빨강", "초록", "파랑", "노랑")

# Indexing
print(colors[0])   # 빨강
print(colors[-1])  # 노랑

# Slicing
print(colors[1:3])  # ('초록', '파랑')

# Length
print(len(colors))  # 4

# Membership
print("빨강" in colors)  # True

# Count and index
numbers = (1, 2, 2, 3, 2)
print(numbers.count(2))   # 3
print(numbers.index(3))   # 3

Tuple Operations

# Concatenation
tuple1 = (1, 2, 3)
tuple2 = (4, 5, 6)
combined = tuple1 + tuple2
print(combined)  # (1, 2, 3, 4, 5, 6)

# Repetition
repeated = (0,) * 5
print(repeated)  # (0, 0, 0, 0, 0)

# Comparison
print((1, 2) < (1, 3))  # True (lexicographic)
print((1, 2) == (1, 2)) # True

Tuple Unpacking

# Basic unpacking
point = (10, 20)
x, y = point
print(x, y)  # 10 20

# Multiple return values
def get_user():
    return "홍길동", 25, "서울"

name, age, city = get_user()
print(name, age, city)

# Extended unpacking (Python 3+)
numbers = (1, 2, 3, 4, 5)
first, *middle, last = numbers
print(first)   # 1
print(middle)  # [2, 3, 4]
print(last)    # 5

# Swapping values
a, b = 1, 2
a, b = b, a
print(a, b)  # 2 1

# Ignoring values
point = (10, 20, 30)
x, _, z = point
print(x, z)  # 10 30

Tuple vs. List

# List: mutable
fruits_list = ["사과", "바나나"]
fruits_list.append("체리")  # ✅
print(fruits_list)

# Tuple: immutable
fruits_tuple = ("사과", "바나나")
# fruits_tuple.append("체리")  # ❌ AttributeError

# Tuples are faster and more memory efficient
import sys
list_data = [1, 2, 3, 4, 5]
tuple_data = (1, 2, 3, 4, 5)
print(sys.getsizeof(list_data))   # 104
print(sys.getsizeof(tuple_data))  # 88

# Tuples can be used as dictionary keys
locations = {
    (0, 0): "원점",
    (1, 0): "동쪽",
    (0, 1): "북쪽"
}
print(locations[(0, 0)])  # 원점

# Lists cannot
# locations = {[0, 0]: "원점"}  # ❌ TypeError

Practical Examples

Student Grade Management

# Student information (tuple for immutable data)
students = [
    ("홍길동", 85, 90, 88),
    ("김철수", 92, 88, 95),
    ("이영희", 78, 85, 82)
]

# Calculate average
def calculate_average(scores):
    name, *grades = scores
    avg = sum(grades) / len(grades)
    return name, avg

for student in students:
    name, avg = calculate_average(student)
    print(f"{name}: Average {avg:.1f} points")

# Best student
best_student = max(students, key=lambda x: sum(x[1:]))
print(f"Highest score: {best_student[0]}")

To-Do List

class TodoList:
    def __init__(self):
        self.tasks = []

    def add(self, task):
        """Add a task"""
        self.tasks.append({"task": task, "done": False})
        print(f"'{task}' added")

    def complete(self, index):
        """Complete a task"""
        if 0 <= index < len(self.tasks):
            self.tasks[index]["done"] = True
            print(f"'{self.tasks[index]['task']}' completed!")

    def remove(self, index):
        """Remove a task"""
        if 0 <= index < len(self.tasks):
            task = self.tasks.pop(index)
            print(f"'{task['task']}' removed")

    def show(self):
        """Display task list"""
        if not self.tasks:
            print("No tasks!")
            return

        print("\n=== To-Do List ===")
        for i, item in enumerate(self.tasks):
            status = "✓" if item["done"] else " "
            print(f"{i+1}. [{status}] {item['task']}")

# Usage example
todo = TodoList()
todo.add("Python 공부하기")
todo.add("운동하기")
todo.add("책 읽기")
todo.show()
todo.complete(0)
todo.show()

Data Analysis

# Sales data (product name, quantity, price)
sales = [
    ("노트북", 5, 1200000),
    ("마우스", 30, 25000),
    ("키보드", 15, 85000),
    ("모니터", 8, 350000)
]

# Calculate total revenue
def calculate_revenue(sales_data):
    total = 0
    for product, quantity, price in sales_data:
        revenue = quantity * price
        total += revenue
        print(f"{product}: {revenue:,}원")
    return total

print("\n=== Revenue by Product ===")
total_revenue = calculate_revenue(sales)
print(f"\nTotal Revenue: {total_revenue:,}원")

# Best selling product
best_seller = max(sales, key=lambda x: x[1])
print(f"\nBest seller: {best_seller[0]} ({best_seller[1]}개)")

# Sort by revenue
sorted_sales = sorted(sales, key=lambda x: x[1] * x[2], reverse=True)
print("\n=== Revenue Ranking ===")
for rank, (product, qty, price) in enumerate(sorted_sales, 1):
    print(f"{rank}. {product}: {qty * price:,}원")

Coordinate Management

# 2D coordinates
points = [(0, 0), (3, 4), (1, 1), (5, 12)]

# Calculate distance from origin
def distance_from_origin(point):
    x, y = point
    return (x**2 + y**2) ** 0.5

# Calculate and sort distances
distances = [(point, distance_from_origin(point)) for point in points]
distances.sort(key=lambda x: x[1])

print("=== Distance from Origin ===")
for point, dist in distances:
    print(f"{point}: {dist:.2f}")

# Farthest point
farthest = max(points, key=distance_from_origin)
print(f"\nFarthest point: {farthest}")

Frequently Asked Questions

Q1. When should I use lists vs. tuples?

A: Decide based on mutability needs

# List: mutable data
shopping_cart = ["사과", "바나나"]
shopping_cart.append("우유")  # cart changes frequently

# Tuple: immutable data
birth_date = (1990, 5, 15)  # birthdate is fixed
coordinates = (37.5665, 126.9780)  # coordinates are fixed

Q2. How do I copy a list?

A: Distinguish between shallow and deep copy

original = [1, 2, 3]

# Reference copy (same object)
ref = original
ref.append(4)
print(original)  # [1, 2, 3, 4] - original also changed!

# Shallow copy (new object)
shallow = original.copy()
# or
shallow = original[:]
# or
shallow = list(original)

shallow.append(5)
print(original)  # [1, 2, 3, 4] - original preserved

# Deep copy (nested list)
import copy
nested = [[1, 2], [3, 4]]
deep = copy.deepcopy(nested)
deep[0].append(3)
print(nested)  # [[1, 2], [3, 4]] - original preserved

Q3. How do I check if a list is empty?

A: There are several ways

my_list = []

# Method 1: Check length
if len(my_list) == 0:
    print("Empty")

# Method 2: Boolean conversion (Pythonic!)
if not my_list:
    print("Empty")

# Method 3: Comparison
if my_list == []:
    print("Empty")

Q4. What should I watch out for when initializing multi-dimensional lists?

A: Be careful with reference copies

# ❌ Wrong way
matrix = [[0] * 3] * 3
matrix[0][0] = 1
print(matrix)  # [[1, 0, 0], [1, 0, 0], [1, 0, 0]] - All rows are the same!

# ✅ Correct way
matrix = [[0] * 3 for _ in range(3)]
matrix[0][0] = 1
print(matrix)  # [[1, 0, 0], [0, 0, 0], [0, 0, 0]] - Normal

Next Steps

You've mastered lists and tuples!

Key Takeaways:
✅ List: mutable, various methods
✅ Tuple: immutable, fast and safe
✅ Indexing, slicing, unpacking
✅ List comprehension
✅ Practical use cases

Next Step: Learn more about collections in Dictionaries and Sets!