Enumerate và Zip

# ❌ CÁCH CŨ - Không tốt
fruits = ["apple", "banana", "cherry"]
for i in range(len(fruits)):
    print(f"{i}: {fruits[i]}")
 
# ✅ CÁCH TỐT - Dùng enumerate
for i, fruit in enumerate(fruits):
    print(f"{i}: {fruit}")

enumerate(iterable, start=0)

# Ví dụ 1: Đánh số từ 0
fruits = ["apple", "banana", "cherry"]
for index, fruit in enumerate(fruits):
    print(f"{index}: {fruit}")
 
# Output:
# 0: apple
# 1: banana
# 2: cherry
 
# Ví dụ 2: Đánh số từ 1
for index, fruit in enumerate(fruits, start=1):
    print(f"{index}: {fruit}")
 
# Output:
# 1: apple
# 2: banana
# 3: cherry

fruits = ["apple", "banana", "cherry"]
result = enumerate(fruits)
print(result)  # <enumerate object>
 
# Chuyển sang list để xem
print(list(enumerate(fruits)))
# [(0, 'apple'), (1, 'banana'), (2, 'cherry')]

menu = ["Pizza", "Burger", "Pasta", "Salad"]
 
print("=== MENU ===")
for number, dish in enumerate(menu, start=1):
    print(f"{number}. {dish}")
 
# Output:
# === MENU ===
# 1. Pizza
# 2. Burger
# 3. Pasta
# 4. Salad

students = ["Alice", "Bob", "Charlie", "David"]
search_name = "Charlie"
 
for index, name in enumerate(students):
    if name == search_name:
        print(f"Tìm thấy {search_name} ở vị trí {index}")
        break
else:
    print(f"Không tìm thấy {search_name}")

with open("data.txt", "r", encoding="utf-8") as file:
    for line_number, line in enumerate(file, start=1):
        print(f"Dòng {line_number}: {line.strip()}")

fruits = ["apple", "banana", "cherry"]
 
# Tạo dict: index -> fruit
fruit_dict = {index: fruit for index, fruit in enumerate(fruits)}
print(fruit_dict)
# {0: 'apple', 1: 'banana', 2: 'cherry'}
 
# Tạo dict: fruit -> index
index_dict = {fruit: index for index, fruit in enumerate(fruits)}
print(index_dict)
# {'apple': 0, 'banana': 1, 'cherry': 2}

numbers = [10, 25, 30, 15, 40, 5]
 
# Tìm tất cả vị trí có giá trị > 20
for index, num in enumerate(numbers):
    if num > 20:
        print(f"Vị trí {index}: {num}")
 
# Output:
# Vị trí 1: 25
# Vị trí 2: 30
# Vị trí 4: 40

# ❌ CÁCH CŨ - Không tốt
names = ["Alice", "Bob", "Charlie"]
ages = [25, 30, 35]
 
for i in range(len(names)):
    print(f"{names[i]} is {ages[i]} years old")
 
# ✅ CÁCH TỐT - Dùng zip
for name, age in zip(names, ages):
    print(f"{name} is {age} years old")

zip(*iterables)

# Ví dụ 1: Kết hợp 2 lists
names = ["Alice", "Bob", "Charlie"]
ages = [25, 30, 35]
 
for name, age in zip(names, ages):
    print(f"{name}: {age}")
 
# Output:
# Alice: 25
# Bob: 30
# Charlie: 35
 
# Ví dụ 2: Kết hợp 3 lists
names = ["Alice", "Bob", "Charlie"]
ages = [25, 30, 35]
cities = ["Hanoi", "HCMC", "Da Nang"]
 
for name, age, city in zip(names, ages, cities):
    print(f"{name}, {age}, {city}")
 
# Output:
# Alice, 25, Hanoi
# Bob, 30, HCMC
# Charlie, 35, Da Nang

names = ["Alice", "Bob"]
ages = [25, 30]
 
result = zip(names, ages)
print(result)  # <zip object>
 
# Chuyển sang list để xem
print(list(zip(names, ages)))
# [('Alice', 25), ('Bob', 30)]

names = ["Alice", "Bob", "Charlie"]
ages = [25, 30]  # Chỉ có 2 phần tử
 
result = list(zip(names, ages))
print(result)
# [('Alice', 25), ('Bob', 30)]
# Charlie bị bỏ qua!

from itertools import zip_longest
 
names = ["Alice", "Bob", "Charlie"]
ages = [25, 30]
 
result = list(zip_longest(names, ages, fillvalue="N/A"))
print(result)
# [('Alice', 25), ('Bob', 30), ('Charlie', 'N/A')]

keys = ["name", "age", "city"]
values = ["Alice", 25, "Hanoi"]
 
person = dict(zip(keys, values))
print(person)
# {'name': 'Alice', 'age': 25, 'city': 'Hanoi'}

scores_math = [85, 90, 78]
scores_english = [88, 82, 95]
scores_science = [92, 88, 80]
 
print("Tổng điểm từng học sinh:")
for i, (math, english, science) in enumerate(zip(scores_math, scores_english, scores_science), start=1):
    total = math + english + science
    print(f"Học sinh {i}: {total} điểm")
 
# Output:
# Tổng điểm từng học sinh:
# Học sinh 1: 265 điểm
# Học sinh 2: 260 điểm
# Học sinh 3: 253 điểm

pairs = [("Alice", 25), ("Bob", 30), ("Charlie", 35)]
 
# Unzip bằng zip với *
names, ages = zip(*pairs)
 
print(names)  # ('Alice', 'Bob', 'Charlie')
print(ages)   # (25, 30, 35)
 
# Chuyển thành lists
names = list(names)
ages = list(ages)

list1 = [1, 2, 3, 4, 5]
list2 = [1, 2, 9, 4, 5]
 
print("So sánh từng phần tử:")
for i, (a, b) in enumerate(zip(list1, list2)):
    if a != b:
        print(f"Vị trí {i}: {a} != {b}")
    else:
        print(f"Vị trí {i}: Giống nhau")
 
# Output:
# Vị trí 0: Giống nhau
# Vị trí 1: Giống nhau
# Vị trí 2: 3 != 9
# Vị trí 3: Giống nhau
# Vị trí 4: Giống nhau

matrix = [
    [1, 2, 3],
    [4, 5, 6],
    [7, 8, 9]
]
 
# Transpose (chuyển vị)
transposed = list(zip(*matrix))
print(transposed)
# [(1, 4, 7), (2, 5, 8), (3, 6, 9)]
 
# Chuyển thành list of lists
transposed = [list(row) for row in zip(*matrix)]
print(transposed)
# [[1, 4, 7], [2, 5, 8], [3, 6, 9]]

names = ["Alice", "Bob", "Charlie"]
ages = [25, 30, 35]
cities = ["Hanoi", "HCMC", "Da Nang"]
 
for index, (name, age, city) in enumerate(zip(names, ages, cities), start=1):
    print(f"{index}. {name} ({age}) - {city}")
 
# Output:
# 1. Alice (25) - Hanoi
# 2. Bob (30) - HCMC
# 3. Charlie (35) - Da Nang

students = ["Alice", "Bob", "Charlie"]
scores_math = [85, 90, 78]
scores_english = [88, 82, 95]
 
print("=== BẢNG ĐIỂM ===")
for rank, (name, math, english) in enumerate(zip(students, scores_math, scores_english), start=1):
    average = (math + english) / 2
    print(f"{rank}. {name} - Math: {math}, English: {english}, Average: {average:.1f}")
 
# Output:
# === BẢNG ĐIỂM ===
# 1. Alice - Math: 85, English: 88, Average: 86.5
# 2. Bob - Math: 90, English: 82, Average: 86.0
# 3. Charlie - Math: 78, English: 95, Average: 86.5

products = ["Laptop", "Mouse", "Keyboard", "Monitor"]
prices = [1000, 20, 50, 300]
quantities = [5, 100, 50, 10]
 
print("=== DANH SÁCH SẢN PHẨM ===")
total_value = 0
 
for index, (product, price, qty) in enumerate(zip(products, prices, quantities), start=1):
    value = price * qty
    total_value += value
    print(f"{index}. {product}: ${price} x {qty} = ${value}")
 
print(f"\nTổng giá trị kho: ${total_value}")
 
# Output:
# === DANH SÁCH SẢN PHẨM ===
# 1. Laptop: $1000 x 5 = $5000
# 2. Mouse: $20 x 100 = $2000
# 3. Keyboard: $50 x 50 = $2500
# 4. Monitor: $300 x 10 = $3000
#
# Tổng giá trị kho: $12500

students = ["Alice", "Bob", "Charlie", "David", "Eve"]
math_scores = [85, 92, 78, 95, 88]
english_scores = [88, 85, 90, 92, 95]
 
# Tính điểm trung bình
averages = []
for name, math, english in zip(students, math_scores, english_scores):
    avg = (math + english) / 2
    averages.append((name, avg))
 
# Tìm điểm cao nhất
max_avg = max(averages, key=lambda x: x[1])
print(f"Học sinh giỏi nhất: {max_avg[0]} ({max_avg[1]} điểm)")
 
# In bảng xếp hạng
print("\n=== BẢNG XẾP HẠNG ===")
for rank, (name, avg) in enumerate(sorted(averages, key=lambda x: x[1], reverse=True), start=1):
    print(f"{rank}. {name}: {avg:.1f} điểm")

# Dữ liệu bán hàng theo quý
quarters = ["Q1", "Q2", "Q3", "Q4"]
revenue = [100000, 120000, 95000, 150000]
expenses = [60000, 70000, 65000, 80000]
growth = ["+5%", "+8%", "-3%", "+12%"]
 
print("=== BÁO CÁO TÀI CHÍNH ===")
for q, rev, exp, gr in zip(quarters, revenue, expenses, growth):
    profit = rev - exp
    print(f"{q}: Revenue ${rev:,} | Expenses ${exp:,} | Profit ${profit:,} | Growth {gr}")
 
# Output:
# === BÁO CÁO TÀI CHÍNH ===
# Q1: Revenue $100,000 | Expenses $60,000 | Profit $40,000 | Growth +5%
# Q2: Revenue $120,000 | Expenses $70,000 | Profit $50,000 | Growth +8%
# Q3: Revenue $95,000 | Expenses $65,000 | Profit $30,000 | Growth -3%
# Q4: Revenue $150,000 | Expenses $80,000 | Profit $70,000 | Growth +12%

items = ["a", "b", "c"]
 
# ❌ TRÁNH
for i in range(len(items)):
    print(f"{i}: {items[i]}")
 
# ✅ TỐT
for i, item in enumerate(items):
    print(f"{i}: {item}")

keys = ["name", "age"]
values = ["Alice", 25]
 
# ❌ TRÁNH
d = {}
for i in range(len(keys)):
    d[keys[i]] = values[i]
 
# ✅ TỐT
d = dict(zip(keys, values))

# Unzip data
pairs = [(1, 'a'), (2, 'b'), (3, 'c')]
numbers, letters = zip(*pairs)
print(numbers)  # (1, 2, 3)
print(letters)  # ('a', 'b', 'c')

# zip() dừng ở ngắn nhất
list1 = [1, 2, 3]
list2 = [4, 5]
 
result = list(zip(list1, list2))
print(result)  # [(1, 4), (2, 5)]
# 3 bị mất!
 
# Dùng zip_longest nếu cần giữ tất cả
from itertools import zip_longest
result = list(zip_longest(list1, list2, fillvalue=0))
print(result)  # [(1, 4), (2, 5), (3, 0)]

text = "Python"
for index, char in enumerate(text):
    print(f"{index}: {char}")
 
# Output:
# 0: P
# 1: y
# 2: t
# 3: h
# 4: o
# 5: n

numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
 
for index, num in enumerate(numbers):
    if num % 2 == 0:
        print(f"Số chẵn {num} ở vị trí {index}")

num1 = [1, 2, 3, 4, 5]
num2 = [10, 20, 30, 40, 50]
 
for a, b in zip(num1, num2):
    print(f"{a} x {b} = {a * b}")

students = ["Alice", "Bob", "Charlie"]
scores = [85, 90, 78]
 
for rank, (student, score) in enumerate(zip(students, scores), start=1):
    grade = "Pass" if score >= 80 else "Fail"
    print(f"{rank}. {student}: {score} - {grade}")