Region Configuration Standard

Do not hard-code AWS region (or other environment-specific settings) inside scripts or service logic. Instead, make region resolution consistent, configurable, and source-of-truth driven.

Practical rules:

• Prefer the standard environment variable: AWS_REGION (or AWS_DEFAULT_REGION).
• If not set, infer from the active AWS credentials/session (e.g., boto3 Session().region_name).
• Allow an explicit override via CLI/config (e.g., --region) when the environment differs from the default.
• Keep service-specific conditionals data-driven (e.g., handle us-east-1 LocationConstraint) but do not embed fixed regions as the primary configuration.

Example pattern:

import os
import boto3
import argparse


def resolve_region(cli_region: str | None) -> str:
    if cli_region:
        return cli_region
    return (
        os.getenv("AWS_REGION")
        or os.getenv("AWS_DEFAULT_REGION")
        or boto3.session.Session().region_name
        or "us-west-2"  # only if you truly want a documented fallback
    )


def main():
    parser = argparse.ArgumentParser()
    parser.add_argument("--region", help="AWS region for all AWS clients")
    args = parser.parse_args()

    region = resolve_region(args.region)
    s3 = boto3.client("s3", region_name=region)

Impact: fewer “works in my account” failures, consistent behavior across deployments (us-east-1 vs us-west-2), and clearer configuration management.