Enumerate & Zip

Enumerate for index and value

Use enumerate() when you need a counter and the item itself.

python
names = ["Ali", "Mona", "Sara"]
for i, name in enumerate(names):
    print(i, name)

Starting from 1

You can start counting at any number.

python
for i, name in enumerate(names, start=1):
    print(i, name)

Zip for parallel lists

zip() pairs items from multiple lists.

python
letters = ["a", "b", "c"]
numbers = [1, 2, 3]
for letter, number in zip(letters, numbers):
    print(letter, number)

zip() stops at the shortest list.

Unzipping with the star operator

You can turn pairs back into two lists.

python
pairs = [("x", 1), ("y", 2)]
letters, numbers = zip(*pairs)
print(list(letters))
print(list(numbers))

Build a dict with zip

This is a clean way to combine keys and values.

python
keys = ["name", "age"]
values = ["Lina", 28]
user = dict(zip(keys, values))

Common mistakes to avoid

• Forgetting that enumerate() starts at 0 by default.
• Assuming zip() will keep going past the shortest list.
• Forgetting to convert the result of zip() into a list if you want to print it.

What you should understand after this lesson

• How to use enumerate() for index + value.
• How to use zip() to walk lists together.
• How to build dictionaries from paired data.