//github.com/wallix/awless in GoLang
AWS CLI is written in Python, and is also open source
aws/aws-cli: Universal Command Line Interface for Amazon Web Services @GitHub
$ complete -C aws_completer aws//aws.amazon.com/cli/
What Is the AWS Command Line Interface? - AWS Command Line Interface
All IaaS (infrastructure as a service) AWS administration, management, and access functions in the AWS Management Console are available in the AWS API and CLI. New AWS IaaS features and services provide full AWS Management Console functionality through the API and CLI at launch or within 180 days of launch.
Python Boto3 API reference