Python Iterate over a List with for Loops

A packing list must print one instruction for each item.

What You Need to Understand

A for loop visits each element of a list in sequence. The loop variable is assigned to the current value; you do not need to manage an index unless you actually need positions.

When to Use It

A packing list must print one instruction for each item.

Step-by-Step Python Example

items = ["cable", "adapter", "mouse"]
for item in items:
    print(f"Pack: {item}")

How the Example Works

The loop body runs once for each of the three list elements. Indentation controls which statement belongs to the loop.

Example Output

Pack: cable
Pack: adapter
Pack: mouse
1 red
2 blue

A Second Example

Compare this smaller variation with the main example, then experiment with your own values.

for position, item in enumerate(["red", "blue"], start=1):
    print(position, item)

Important Behavior and Edge Cases

Changing the collection while looping can skip or repeat items. Do not write for index in range(len(items)) unless position access is needed.

Try It Yourself

Print each item with an increasing number using enumerate(items, start=1).

Common Beginner Mistakes

Changing the collection while looping can skip or repeat items. Do not write for index in range(len(items)) unless position access is needed.
Assuming every sequence operation modifies the original data or that a tuple makes nested mutable objects immutable.

Key Takeaways

A for loop visits each element of a list in sequence.
The loop body runs once for each of the three list elements.
Changing the collection while looping can skip or repeat items.