Answers by Sentry

Access the index of a for loop

David Y.

The Problem

How do I access the index when iterating over a sequence inside a for loop?

The Solution

We can use Python’s built-in enumerate() function to do this. For each item in an iterable sequence such as a list, this function will return a tuple containing the item’s index and the item itself. Therefore, our code will look like this:

products = ["Apples", "Oranges", "Bananas"]

for idx, product in enumerate(products):
    print(f"{idx}: {product}")

This code will produce the following output:

0: Apples
1: Oranges
2: Bananas

If we would prefer to start the index from 1 (or any other number), we can specify this using enumerate()’s start parameter, as below:

products = ["Apples", "Oranges", "Bananas"]

for idx, product in enumerate(products, start=1):
    print(f"{idx}: {product}")

This will produce the following output:

1: Apples
2: Oranges
3: Bananas

The index can also be accessed without using the enumerate() function by iterating over the length of the iterable sequence as below:

products = ["Apples", "Oranges", "Bananas"]

for idx in range(len(products)):
    print(f"{idx}: {products[idx]}")

This code will produce the following output:

0: Apples
1: Oranges
2: Bananas

Get Started With Sentry

Get actionable, code-level insights to resolve Python performance bottlenecks and errors.

  1. Create a free Sentry account

  2. Create a Python project and note your DSN

  3. Grab the Sentry Python SDK

pip install --upgrade sentry-sdk
  1. Configure your DSN
import sentry_sdk

sentry_sdk.init(
    "https://<key>@sentry.io/<project>",

    # Set traces_sample_rate to 1.0 to capture 100%
    # of transactions for performance monitoring.
    # We recommend adjusting this value in production.
    traces_sample_rate=1.0,
)

Loved by over 4 million developers and more than 90,000 organizations worldwide, Sentry provides code-level observability to many of the world’s best-known companies like Disney, Peloton, Cloudflare, Eventbrite, Slack, Supercell, and Rockstar Games. Each month we process billions of exceptions from the most popular products on the internet.

learn more about sentryjoin our discord
Share on Twitter
Bookmark this page
Ask a questionJoin the discussion

Related Answers

A better experience for your users. An easier life for your developers.

Try Sentry For FreeRequest a Demo
    TwitterGitHubDribbbleLinkedinDiscord
© 2024 • Sentry is a registered Trademark
of Functional Software, Inc.