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enumerate() in Python: the item and its index at once

Sometimes you need both the item and its position in the loop. enumerate() hands you both — no clumsy counter to maintain by hand.

The big idea

enumerate(seq) yields (index, item) pairs, so a loop gets each item together with its position.

See it in code

1The basics

enumerate(seq) yields (index, item) pairs. Unpack them into i and the item, and the loop gets each value together with its position:

python
names = ["Blaze", "Nova", "Rex"]
for i, name in enumerate(names):
    print(i, name)
Run it — each item arrives with its index:
0 Blaze
1 Nova
2 Rex

No counter to maintain — enumerate handed back 0, 1, 2 alongside each name, in one clean step.

2A step further

The index is a number, so you can compute with it. Here we turn each enemy's place in line into an evenly spaced x-position:

python
wave = ["enemy", "enemy", "enemy"]
for i, e in enumerate(wave):
    print(f"enemy {i} -> x={55 + i * 74}")
Run it — each index becomes a position:
enemy 0 -> x=55
enemy 1 -> x=129
enemy 2 -> x=203

55 + i * 74 maps each index to a spot. Now let's run that on real Enemy objects and actually place them.

3In our world

We have a list of enemies stacked at the same spot and want to spread them out. enumerate(wave) gives us i alongside each enemy, so we set each one's x from its place in line — the exact formula from the warm-up:

python
from game import Stage, Enemy

screen = Stage.create()
Stage.clear(screen)

wave = [Enemy(0, 90) for _ in range(6)]
for i, enemy in enumerate(wave):
    enemy.x = 55 + i * 74
    print(f"enemy {i} -> x={enemy.x}")
    enemy.draw(screen)
Run it — each enemy is placed by its index:
enemy 0 -> x=55
enemy 1 -> x=129
enemy 2 -> x=203
enemy 3 -> x=277
enemy 4 -> x=351
enemy 5 -> x=425
A row of six purple enemy sprites evenly spaced near the top of a dark play area.

enumerate unpacked each pair into i and enemy in one clean step. It starts at 0 by default, but enumerate(wave, start=1) would number them from 1 — handy for human-facing lists.

The same idea, everywhere

Any time you loop and need positions, enumerate beats a manual counter: numbering menu options, labeling rows of data, finding the index of a match, laying out a grid. It's clearer than tracking i += 1 yourself, and impossible to forget to increment.

Try it yourself

Add start=1 and watch the printed numbers shift. Then use the index to alternate color or spacing — if i % 2 == 0 for every other enemy — a common 'stripe' pattern.

The common mistake

Falling back to for i in range(len(wave)) and indexing wave[i] everywhere. It works, but it's noisier and error-prone. When you need both the index and the item, enumerate is the idiomatic, less-buggy choice.

What it unlocks

enumerate sharpens for loops over lists, and pairs naturally with list indexing.

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