Hands-on LabIT Fundamentals · Module 05

Lab: Module 05: JSON, YAML, and Configuration Files

Lab 09: Working with JSON and YAML

Objective

Practice reading, writing, and validating JSON and YAML documents. Convert between formats and work with environment variables.

Duration

20 to 30 minutes

Prerequisites

  • Windows: Git Bash, WSL, or PowerShell. Python 3 installed.
  • macOS: Terminal.app. Python 3 installed (brew install python3 or from python.org).
  • Linux: Any terminal. Python 3 installed (sudo apt install python3).

Instructions

Part 1: JSON Validation

  1. Create a file called server-config.json. Type it manually to build muscle memory:
{
  "server": {
    "host": "0.0.0.0",
    "port": 3000,
    "debug": false
  },
  "database": {
    "engine": "postgres",
    "host": "localhost",
    "port": 5432,
    "name": "bootcamp",
    "credentials": {
      "username": "admin",
      "password": "changeme"
    }
  },
  "features": {
    "enableCache": true,
    "maxConnections": 100,
    "allowedOrigins": ["https://example.com", "https://app.example.com"]
  }
}
  1. Validate it:

macOS / Linux / WSL / Git Bash:

python3 -m json.tool < server-config.json

Windows PowerShell:

Get-Content server-config.json | python -m json.tool
# Or use Python directly:
python -c "import json; json.load(open('server-config.json')); print('Valid JSON')"
  1. Intentionally break the JSON (remove a comma, use single quotes, add a trailing comma) and observe the error messages. Fix each one.

Part 2: YAML Conversion

  1. Create a file called server-config.yaml that represents the exact same data as the JSON above, but in YAML format:
server:
  host: "0.0.0.0"
  port: 3000
  debug: false

database:
  engine: postgres
  host: localhost
  port: 5432
  name: bootcamp
  credentials:
    username: admin
    password: changeme

features:
  enableCache: true
  maxConnections: 100
  allowedOrigins:
    - https://example.com
    - https://app.example.com
  1. Validate your YAML:

macOS / Linux / WSL / Git Bash:

python3 -c "import yaml; print(yaml.safe_load(open('server-config.yaml')))"

💡Note: If you get ModuleNotFoundError: No module named 'yaml', install it first:

pip3 install pyyaml

Windows PowerShell:

python -c "import yaml; print(yaml.safe_load(open('server-config.yaml')))"
  1. Compare the two files: which is more readable? Which is shorter? Which supports comments?

Part 3: AWS IAM Policy (JSON)

  1. Create a file called s3-read-policy.json:
{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Action": [
        "s3:GetObject",
        "s3:ListBucket"
      ],
      "Resource": [
        "arn:aws:s3:::my-bootcamp-bucket",
        "arn:aws:s3:::my-bootcamp-bucket/*"
      ]
    }
  ]
}

  1. Answer these questions by reading the policy:

    • What actions are allowed?
    • What resource(s) can be accessed?
    • Can this policy delete objects? Why or why not?

  2. Modify the policy to also allow s3:PutObject (uploading files). Validate the JSON.

Part 4: Environment Variables

macOS / Linux / WSL / Git Bash

# Set environment variables
export APP_ENV="development"
export DB_HOST="localhost"
export DB_PORT="5432"
export SECRET_KEY="my-super-secret-key-123"

# Verify they're set
echo $APP_ENV
echo $DB_HOST
env | grep DB_

Windows PowerShell

# Set environment variables (session only)
$env:APP_ENV = "development"
$env:DB_HOST = "localhost"
$env:DB_PORT = "5432"
$env:SECRET_KEY = "my-super-secret-key-123"

# Verify
echo $env:APP_ENV
echo $env:DB_HOST
Get-ChildItem env: | Where-Object { $_.Name -like "DB_*" }

Windows Command Prompt (cmd)

set APP_ENV=development
set DB_HOST=localhost
echo %APP_ENV%

Read Variables in Python (all platforms)

Create read_env.py:

import os

env = os.getenv("APP_ENV", "production")
db_host = os.getenv("DB_HOST", "127.0.0.1")
db_port = os.getenv("DB_PORT", "5432")

print(f"Environment: {env}")
print(f"Database: {db_host}:{db_port}")

Run it:

python3 read_env.py       # macOS / Linux / WSL
python read_env.py        # Windows

Now unset APP_ENV and run again to see the default value:

macOS / Linux / WSL:

unset APP_ENV
python3 read_env.py

Windows PowerShell:

Remove-Item env:APP_ENV
python read_env.py

Validation

  • Created and validated server-config.json (and fixed intentional errors)
  • Converted to server-config.yaml and validated
  • Read and modified an IAM policy JSON document
  • Set, read, and used environment variables on your platform
  • Ran a Python script that reads environment variables with defaults

AWS Bootcamp: From Novice to Architect Author: Samuel Ogunti License: CC BY-NC 4.0

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