📝 Iterating Lists — Processing Collections

The most powerful use of loops: efficiently processing every item in a list.

🎯 Basic List Iteration

fruits = ["apple", "banana", "orange"]
for fruit in fruits:
    print(fruit)
# Output: apple, banana, orange

💡 Common Patterns

Example 1: Process each item

scores = [85, 92, 78, 95]
for score in scores:
    print(f"Score: {score}")

Example 2: Modify items

numbers = [1, 2, 3, 4]
for i in range(len(numbers)):
    numbers[i] = numbers[i] * 2  # Double each number
print(numbers)  # [2, 4, 6, 8]

Example 3: Calculate total

prices = [10.99, 5.50, 25.00]
total = 0
for price in prices:
    total = total + price
print(f"Total: ${total}")  # Total: $41.49

🔍 Getting Both Index and Value with enumerate()

fruits = ["apple", "banana", "orange"]
for index, fruit in enumerate(fruits):
    print(f"{index}: {fruit}")
# Output:
# 0: apple
# 1: banana
# 2: orange

🎨 Practical Applications

Example 1: Find position of item

grades = ["A", "B", "C", "B", "A"]
for index, grade in enumerate(grades):
    if grade == "C":
        print(f"C grade at position {index}")

Example 2: Update specific items

items = ["apple", "banana", "orange"]
for index, item in enumerate(items):
    if item == "banana":
        items[index] = "pear"
print(items)  # ['apple', 'pear', 'orange']

📊 Iteration Methods

🔑 Key Takeaways

🔗 What's Next?

Learn Loop Patterns for common use cases!

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