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The SWL Library Management System uses environment variables and a centralized configuration file to manage application settings. All configuration is handled through config.py.

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Environment Variables

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Security Settings

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SECRET_KEY

Required for production The secret key is used for session management, CSRF protection, and other security features. 
SECRET_KEY=your-secure-random-key-here
Never use the default development key in production. Generate a secure random key using:
python -c "import secrets; print(secrets.token_hex(32))"
Default: 'clave-secreta-para-desarrollo' (development only) Location: config.py:6

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Database Configuration

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DATABASE_URL

Specifies the database connection string. The system supports both SQLite and PostgreSQL. 
# PostgreSQL (recommended for production)
DATABASE_URL=postgresql://username:password@localhost/library_db

# SQLite (default for development)
# If not set, uses: sqlite:///instance/app.db
Default: sqlite:///instance/app.db Location: config.py:10-11
PostgreSQL is strongly recommended for production deployments due to better concurrency handling and performance.

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Business Parameters

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PENALTY_FEE_PER_DAY

Defines the daily penalty fee (in currency units) charged for overdue book loans. 
PENALTY_FEE_PER_DAY=5000.0
Default: 5000.0 Type: Float Location: config.py:21 Usage: This value is used in the Loan.penalty_fee property (models.py:89) to calculate late fees for overdue books.

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Scheduler Configuration

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SCHEDULER_TIMEZONE

Sets the timezone for scheduled tasks (e.g., overdue loan checks). 
SCHEDULER_TIMEZONE="America/Bogota"
Default: "America/Bogota" Location: config.py:15 Scheduled Tasks:
  • Overdue loan check runs daily at 00:01 AM (app/__init__.py:34)
  • Uses APScheduler with cron triggers

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SCHEDULER_API_ENABLED

Controls whether the scheduler API endpoints are exposed. 
SCHEDULER_API_ENABLED=False
Default: False Location: config.py:14
Keep this disabled in production unless you specifically need programmatic scheduler control.

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Session Configuration

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PERMANENT_SESSION_LIFETIME

Defines how long user sessions remain active. 
PERMANENT_SESSION_LIFETIME=timedelta(minutes=30)
Default: 30 minutes Location: config.py:17 Note: Sessions are made permanent by default in app/__init__.py:60-61

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Application Identity

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APP_NAME

The application display name used throughout the interface. 
APP_NAME="SWL"
Default: "SWL" Location: config.py:27

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LIBRARY_NAME

The library institution name. 
LIBRARY_NAME="SWL"
Default: "SWL" Location: config.py:28

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Logging Configuration

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LOG_FILE

Path to the application log file. Default: logs/library.log Location: config.py:24 Log Rotation Settings (app/__init__.py:49):
  • Maximum file size: 1MB
  • Backup count: 3 files
  • Format: %(asctime)s %(levelname)s: %(message)s [in %(pathname)s:%(lineno)d]

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Database Configuration Details

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SQLAlchemy Settings

SQLALCHEMY_TRACK_MODIFICATIONS=False
Default: False Location: config.py:12 Disables Flask-SQLAlchemy event system to save memory.

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Example Configuration Files

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Development (.env)

# Development configuration
SECRET_KEY=dev-key-change-in-production
DATABASE_URL=sqlite:///instance/app.db
PENALTY_FEE_PER_DAY=5000.0
SCHEDULER_TIMEZONE=America/Bogota

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Production (.env)

# Production configuration
SECRET_KEY=<generate-secure-key>
DATABASE_URL=postgresql://library_user:secure_password@localhost/library_production
PENALTY_FEE_PER_DAY=5000.0
SCHEDULER_TIMEZONE=America/Bogota
Production environment files should:
  • Never be committed to version control
  • Have restricted file permissions (600)
  • Use strong, unique values for all secrets
  • Use PostgreSQL instead of SQLite

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Configuration Class Structure

All configuration is centralized in the Config class (config.py:4): 
from config import Config

app = create_app(config_class=Config)
The configuration is loaded during application factory initialization in app/__init__.py:21.

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See Also