Is the enumerate, zip, range lesson free?

Yes. The first 5 lessons on PyRun are free forever — no signup, no card. enumerate, zip, range runs real Python in your browser via Pyodide.

How long does the enumerate, zip, range lesson take?

About 6 minutes end-to-end. It's a hands-on lesson — you read a paragraph, edit the code, and run it in the same tab.

Do I need to install Python to try the enumerate, zip, range lesson?

No install required. PyRun runs real CPython in your browser via Pyodide (Python compiled to WebAssembly). Works on Chrome, Firefox, Safari, and Edge — desktop or mobile.

What level is the enumerate, zip, range lesson?

Beginner level. No prior Python required — good starting point.

← All lessons

Beginner·6 min·basics · iteration

enumerate, zip, range

You’ll be able to

Iterate with enumerate() for indexed loops
Loop over multiple sequences in parallel with zip()
Reverse iteration with reversed()
Sort iterables by custom keys with sorted(..., key=...)

Why this matters

enumerate and zip are the mark of Pythonic code; reviewers flag for i in range(len(x)) on sight. dict.items() shows up in every config loader, template renderer, and ORM serializer in the ecosystem.

Common pitfalls

Writing for i in range(len(lst)): lst[i] instead of enumerate(lst). It works but reads as non-Pythonic in code review.
Assuming zip errors on unequal lengths. It silently truncates; use zip(a, b, strict=True) on Python 3.10+ to catch mismatches.
Calling .items() and unpacking wrong: for k, v in d.items() is correct; for k in d.items() gives you tuples.

Three iteration patterns you'll reach for every day.

`enumerate(seq, start=0)`

Gives you (index, value) tuples. Stop writing for i in range(len(x)).

`zip(a, b)`

Walks multiple sequences in parallel. Stops at the shortest one.

`range(start, stop, step)`

Lazy sequence of integers. Convert with list(range(...)) if you need a list.

Try it

Use zip to build a dict from names and years.
Print every other item of a list using enumerate + a check on the index.

Practice

3 graded exercises

Write the code, click Check. We’ll tell you exactly what to fix.

Progress0 / 3

Exercise 1
Given fruits = ["apple", "banana", "cherry"], use enumerate (starting at 1) to print each fruit as "1. apple", "2. banana", "3. cherry" — one per line.
Exercise 2
Use zip to pair names = ["Ada", "Grace", "Linus"] with years = [1815, 1906, 1969], build a dict name→year, and print it. Expected: {'Ada': 1815, 'Grace': 1906, 'Linus': 1969}.
Exercise 3
Using range and a step, print every odd number from 1 to 15 inclusive on a single line separated by spaces. Expected exactly: 1 3 5 7 9 11 13 15.

← PreviousTruthiness & None Next →Functions

enumerate, zip, range

You’ll be able to

Iterate with enumerate() for indexed loops
Loop over multiple sequences in parallel with zip()
Reverse iteration with reversed()
Sort iterables by custom keys with sorted(..., key=...)

Why this matters

Common pitfalls

Writing for i in range(len(lst)): lst[i] instead of enumerate(lst). It works but reads as non-Pythonic in code review.
Assuming zip errors on unequal lengths. It silently truncates; use zip(a, b, strict=True) on Python 3.10+ to catch mismatches.
Calling .items() and unpacking wrong: for k, v in d.items() is correct; for k in d.items() gives you tuples.

Three iteration patterns you'll reach for every day.

`enumerate(seq, start=0)`

Gives you (index, value) tuples. Stop writing for i in range(len(x)).

`zip(a, b)`

Walks multiple sequences in parallel. Stops at the shortest one.

`range(start, stop, step)`

Lazy sequence of integers. Convert with list(range(...)) if you need a list.

Try it

Use zip to build a dict from names and years.
Print every other item of a list using enumerate + a check on the index.

Practice

3 graded exercises

Write the code, click Check. We’ll tell you exactly what to fix.

Progress0 / 3

Exercise 1
Given fruits = ["apple", "banana", "cherry"], use enumerate (starting at 1) to print each fruit as "1. apple", "2. banana", "3. cherry" — one per line.
Exercise 2
Use zip to pair names = ["Ada", "Grace", "Linus"] with years = [1815, 1906, 1969], build a dict name→year, and print it. Expected: {'Ada': 1815, 'Grace': 1906, 'Linus': 1969}.
Exercise 3
Using range and a step, print every odd number from 1 to 15 inclusive on a single line separated by spaces. Expected exactly: 1 3 5 7 9 11 13 15.