For Loops with Lists

Iterate over lists with for loops

For Loops with Lists — Processing Every Item

What Is a For Loop?

A for loop lets you do something with every item in a list (or any collection). Instead of writing item[0], item[1], item[2]... manually, the loop handles the repetition for you.

� **Analogy:** A for loop is like a conveyor belt. Each item passes by, you grab it, do something with it, and the next one comes along.

Syntax

python

fruits = ["apple", "banana", "cherry"]

for fruit in fruits:
    print(fruit)

Output:

apple
banana
cherry

Part	What it means
`for`	Keyword that starts the loop
`fruit`	Loop variable — you name this! It takes each item's value, one at a time
`in`	Keyword meaning "take each item from"
`fruits`	The collection to loop over
`:`	Colon ends the loop header
`print(fruit)`	Body — runs once for each item (must be indented!)

How It Works

python

numbers = [10, 20, 30]

for n in numbers:
    result = n * 2
    print(f"{n} doubled is {result}")

Step by step execution:

Iteration	`n` equals	Code runs	Output
1st	`10`	`10 * 2 = 20`	"10 doubled is 20"
2nd	`20`	`20 * 2 = 40`	"20 doubled is 40"
3rd	`30`	`30 * 2 = 60`	"30 doubled is 60"

The loop body runs 3 times total — once for each item. When there are no more items, the loop ends and Python continues with whatever follows.

� **You choose the variable name.** `for fruit in fruits:` or `for item in items:` or `for x in xs:` — pick something descriptive!

Why Use Loops?

Without loops, you'd have to write the same code over and over — one line per item. With loops:

**Process a shopping cart** — calculate total price of every item

**Send emails** — loop through a list of recipients

**Search** — check every item for a match

**Calculate stats** — sum, average, min, max of all numbers

**Generate reports** — format and output every row of data

Common Mistakes

❌ Wrong	Why	✅ Right
`for fruit in fruits:` then `print(fruits)`	Prints the full list each time instead of item	Use the loop variable: `print(fruit)`
`for fruit in fruits:` with no indented body	Colon requires at least one indented line	Indent the code you want repeated
`for i in range(len(list)):` used unnecessarily	More complex than needed	`for item in list:` is cleaner
Modifying a list while looping over it	Skips items or causes bugs	Loop over a copy: `for item in list[:]:`

Your Turn!

Create a list names = ["Alice", "Bob", "Charlie"]. Write a for loop that prints: "Hello, {name}! 👋" for each name.

💡Need a hint? (3 available)

#1The loop variable takes each item's value one at a time

#2Use the loop variable inside the body

#3Everything inside the loop must be indented

🔑Show solution (try it yourself first!)

names = ["Alice", "Bob", "Charlie"]
for name in names:
    print(f"Hello, {name}! 👋")

✏️ Code Editor

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📤 Output

Write your solution and click "Run Code" to test it!

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