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How do I get the index while looping in Python?

Python 2 min read Full lesson: Python Loops and List Comprehension
Short answer

Use enumerate(items), which yields (index, value) pairs. Pass start=1 when the numbers are for humans to read.

python
lessons = ["Intro", "Basics", "Loops"]

for index, lesson in enumerate(lessons):
    print(index, lesson)        # 0 Intro, 1 Basics, 2 Loops

for number, lesson in enumerate(lessons, start=1):
    print(f"Lesson {number}: {lesson}")   # Lesson 1: Intro, ...

start=1 is the part people miss and then compensate for with index + 1 scattered through their output strings.

#The anti-pattern it replaces

python
for i in range(len(lessons)):     # works, but verbose
    print(i, lessons[i])

If you only need the values, loop over the list directly. If you need the position too, that is what enumerate is for. range(len(...)) is almost never the right answer.

#It works in comprehensions too

python
numbered = [f"{i}. {name}" for i, name in enumerate(lessons, 1)]

#Two lists at once

enumerate gives you index plus one sequence. For two sequences, use zip:

python
for name, count in zip(names, counts):
    print(name, count)

And for both at once:

python
for i, (name, count) in enumerate(zip(names, counts), 1):
    print(i, name, count)

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