================================================================================
PRACTICAL PYTHON SCRIPTING - CHALLENGE 1 SOLUTION
Chapter 2: Configuration & Environment Variables
Challenge: Load and Display Configuration
================================================================================

PROBLEM:
Create a script that:
1. Creates a .env file with database settings
2. Loads it with load_dotenv()
3. Displays all settings (except the password)

SOLUTION:
================================================================================

from dotenv import load_dotenv
import os
from pathlib import Path

# Step 1: Create a .env file (if it doesn't exist)
env_file = Path(__file__).parent / ".env"

if not env_file.exists():
    print("📝 Creating .env file...")
    env_content = """# Database Configuration
DB_HOST=localhost
DB_NAME=learning_blog
DB_USER=philip
DB_PASS=AsT@1sAd3mon
DB_PORT=3306
DB_CHARSET=utf8mb4

# Application Settings
DEBUG=false
LOG_LEVEL=info
"""
    env_file.write_text(env_content)
    print(f"✅ Created .env file at {env_file}\n")
else:
    print(f"✅ .env file already exists at {env_file}\n")

# Step 2: Load the .env file
load_dotenv(env_file)
print("📂 Loading configuration from .env...\n")

# Step 3: Display configuration (except password)
print("=" * 60)
print("CONFIGURATION")
print("=" * 60)

# Database settings
print("\n🗄️ Database Settings:")
print(f"   Host: {os.environ.get('DB_HOST')}")
print(f"   Name: {os.environ.get('DB_NAME')}")
print(f"   User: {os.environ.get('DB_USER')}")
print(f"   Port: {os.environ.get('DB_PORT')}")
print(f"   Charset: {os.environ.get('DB_CHARSET')}")
print(f"   Password: {'*' * 10} (hidden for security)")

# Application settings
print("\n⚙️ Application Settings:")
print(f"   Debug: {os.environ.get('DEBUG')}")
print(f"   Log Level: {os.environ.get('LOG_LEVEL')}")

print("\n" + "=" * 60)
print("✅ Configuration loaded successfully!")
print("=" * 60)

================================================================================

HOW IT WORKS:
================================================================================

Step 1: CREATE THE .ENV FILE
if not env_file.exists():
    env_file.write_text(env_content)

- Check if .env exists using .exists()
- If not, create it with .write_text()
- This makes the script self-contained (creates its own config)

Step 2: LOAD THE CONFIGURATION
load_dotenv(env_file)

- Specify the exact path to the .env file
- Reads the file and loads all KEY=VALUE pairs
- Now all variables are available in os.environ

Step 3: DISPLAY SETTINGS
os.environ.get('DB_HOST')

- Use .get() to safely access variables
- Display all settings except the password
- Password is replaced with asterisks for security

Why hide the password?
- Good security practice
- Shows that you're thinking about secrets
- Prevents accidental exposure in logs/output

================================================================================

TESTING THE SOLUTION:
================================================================================

1. Create a file called "config_loader.py" with the solution

2. Run it:
   python config_loader.py

   Output on first run:
   📝 Creating .env file...
   ✅ Created .env file at /path/to/script/.env

   📂 Loading configuration from .env...

   ============================================================
   CONFIGURATION
   ============================================================

   🗄️ Database Settings:
      Host: localhost
      Name: learning_blog
      User: philip
      Port: 3306
      Charset: utf8mb4
      Password: ********** (hidden for security)

   ⚙️ Application Settings:
      Debug: false
      Log Level: info

   ============================================================
   ✅ Configuration loaded successfully!
   ============================================================

3. Run it again (second run):
   ✅ .env file already exists at /path/to/script/.env

   (The file is only created once)

4. Check that the .env file exists:
   ls -la .env
   cat .env

   Should show:
   # Database Configuration
   DB_HOST=localhost
   ...

================================================================================

WHAT EACH PART DOES:
================================================================================

from dotenv import load_dotenv
- Import the load_dotenv function
- This function reads .env files

import os
- Import os module for accessing environment variables
- os.environ is a dictionary of all environment variables

from pathlib import Path
- Import Path for file operations

Path(__file__).parent
- Get the directory containing this script
- Used to find/create .env in the script's directory

env_file.exists()
- Check if the .env file exists
- Returns True/False

env_file.write_text(content)
- Create the file and write text to it
- Creates the file if it doesn't exist
- Overwrites if it does exist (use with care!)

load_dotenv(env_file)
- Load variables from the specified .env file
- After this, variables are available in os.environ

os.environ.get('KEY')
- Get an environment variable safely
- Returns None if the variable doesn't exist
- Doesn't crash like os.environ['KEY'] would

================================================================================

ALTERNATIVE APPROACHES:
================================================================================

Approach 1: Load .env without creating it
from dotenv import load_dotenv
import os

load_dotenv()  # Searches for .env in current directory and parents

# Just load it, don't create it
# .env must already exist

Approach 2: Multiple environment-specific .env files
from dotenv import load_dotenv
import os

# Load based on environment
env = os.environ.get('APP_ENV', 'development')
load_dotenv(f'.env.{env}')

# Uses: .env.development, .env.production, etc.

Approach 3: Display all variables
from dotenv import load_dotenv
import os

load_dotenv()

print("All loaded variables:")
for key, value in os.environ.items():
    if key.startswith('DB_') or key.startswith('APP_'):
        print(f"  {key}: {value}")

================================================================================

SECURITY CONSIDERATIONS:
================================================================================

1. HIDING THE PASSWORD
   print(f"Password: {'*' * 10}")

   Don't accidentally print the actual password!
   This is why we explicitly hide it.

2. FILE PERMISSIONS
   After running this script:
   chmod 600 .env

   Make sure only the owner can read the file.

3. .gitignore
   Make sure .env is in .gitignore:
   echo ".env" >> .gitignore

   Never commit real credentials to Git!

4. .env.example
   Create a template for other developers:
   DB_HOST=localhost
   DB_NAME=learning_blog
   DB_USER=your_username
   DB_PASS=your_password_here

   Commit this to Git (without real values).

================================================================================

REAL-WORLD USAGE:
================================================================================

In actual scripts, you'd do this once at startup:

def load_configuration():
    from dotenv import load_dotenv
    import os

    load_dotenv()  # Load from .env

    config = {
        'db_host': os.environ.get('DB_HOST', 'localhost'),
        'db_name': os.environ.get('DB_NAME'),
        'db_user': os.environ.get('DB_USER'),
        'db_pass': os.environ.get('DB_PASS'),
        'db_port': int(os.environ.get('DB_PORT', '3306')),
    }

    return config

# At the start of your script:
config = load_configuration()

# Then use throughout your script:
print(f"Connecting to {config['db_host']}...")

================================================================================

KEY TAKEAWAYS:
================================================================================

✅ load_dotenv() loads .env files into os.environ
✅ os.environ.get() safely accesses variables
✅ Always hide passwords in output
✅ Create .env files outside web root
✅ Never commit .env to Git
✅ Create .env.example as a template
✅ Use chmod 600 on .env for security
✅ This pattern works on Windows, Mac, and Linux

The pattern you've learned:
1. Create/load .env file
2. Use load_dotenv() to load it
3. Access with os.environ.get()
4. Display safely (hide secrets)

This is how ALL production Python scripts handle configuration!

================================================================================