Build: PocketAWS—A Simple, Friendly Way to Parse AWS ARNs

Build: PocketAWS—A Simple, Friendly Way to Parse AWS ARNs

Table of Contents

• Introduction
• Setup and Usage
• Troubleshooting
• Closing Thoughts

Introduction

If you've worked in AWS for any length of time, you've run across ARNs (Amazon Resource Names). They seem to be everywhere—popping up in logs, templates, resource screens, and permissions policies. But even though ARNs are essential, they aren't always easy to understand at a glance.

That's why we built the PocketAWS ARN Parser: a lightweight, human-friendly tool that helps you break down any AWS ARN into its key parts. Whether you're troubleshooting, documenting, or just learning, this tool makes the invisible structure of ARNs visible, quickly and cleanly.

AWS offers plenty of services, but no simple meta-tool for understanding ARNs across the platform. PocketAWS is our small but mighty answer to that gap.

Setup and Usage

Requirements:

• Python 3.7 or higher
• No external Python packages needed (pure built-in Python)

Download the PocketAWS ARN Parser: 

Download pocketaws_arn.py here:  Github Gist  

Optional: Set Up a Virtual Environment

While the PocketAWS ARN Parser has no external dependencies, we recommend using a Python virtual environment for best practices and future expansion. 

Bash

# Create a virtual environment 
python3 -m venv pocketaws_env
 
# Activate it (Linux/Mac) 
source pocketaws_env/bin/activate 

# Activate it (Windows) 
pocketaws_env\Scripts\activate   

Once inside the virtual environment, you’re ready to go.

Running the Parser

After saving the script (pocketaws_arn.py), simply run: 

Bash

python3 pocketaws_arn.py \
    "arn:aws:lambda:us-west-2:123456789012:function:my-test-func"   

Optional: Use --tree to see the output in a friendly tree format: 

Bash

python3 pocketaws_arn.py "arn:aws:s3:::example-bucket" --tree   

What the Tool Will Do

• Parse and validate the provided AWS ARN
• Display parsed parts clearly in the terminal
• Warn about missing fields (like region or account ID)
• Save the parsed output automatically to a file called parsed_arn_output.json

Important Notes

• No AWS authentication is needed — this tool only analyzes the ARN format.
• If you modify or extend the script in the future (for example, adding color support), you can easily install packages inside the virtual environment.

Troubleshooting

If you run into any issues, here are some quick tips:

"command not found" when trying to run the script

Try using python3 instead of python:

Bash

python3 pocketaws_arn.py "your-arn-here"   

"Permission denied" or script won't execute

Make the script executable:

 

Bash

chmod +x pocketaws_arn.py   

"Module not found" error

Ensure your virtual environment is activated:

Bash

source pocketaws_env/bin/activate   

"[ERROR] Invalid ARN format"

Double-check your ARN. It should look like: 

Bash

arn:partition:service:region:account-id:resource   

Example: 

Bash

arn:aws:lambda:us-east-1:123456789012:function:my-function   

Parsed output not saved to file

Check that you have write permissions in the current directory.

Closing Thoughts

Thank you for trying out the PocketAWS ARN Parser!

We built this tool with a simple goal: to make working with AWS ARNs a little easier, a little friendlier, and a lot more human. AWS can be overwhelming, but once you have a clean way to understand and work with ARNs, you're well on your way to mastering your cloud environment.

Stay tuned — PocketAWS is just getting started! We're already building companion tools like the PocketAWS Fetcher to help you gather ARNs even faster across services and regions.

If you find PocketAWS helpful, we’d love for you to share it, suggest ideas, or even build on it yourself. Here's to a more open, practical, and empowering AWS experience—one small tool at a time.

Happy ARN hunting! 🚀🔎

Need AWS Expertise?

We'd love to help you with your AWS projects.  Feel free to reach out to us at info@pacificw.com.

Written by Aaron Rose, software engineer and technology writer at Tech-Reader.blog.