Environment Variables Reference - Muebles Roble

Overview

The Muebles Roble application uses environment variables for configuration management, loaded from a .env file using python-dotenv.

Environment variables allow you to configure the application without hardcoding values, making it easy to switch between development, testing, and production environments.

Environment File Setup

Creating the .env File

Copy the template:

cp .env-template .env

Edit .env with your configuration

Never commit .env to version control. It’s already included in .gitignore.

Template File

The .env-template provides a reference:

.env-template

FLASK_APP=app.py
FLASK_ENV=development

DB_USER=example_user
DB_PASSWORD=example_password
DB_HOST=localhost
DB_PORT=3306
DB_NAME=example_db

Configuration Variables

Flask Configuration

FLASK_APP

string

default:"app.py"

Specifies the application entry point for Flask CLI commands.

FLASK_APP=app.py

FLASK_ENV

string

default:"development"

Sets the Flask environment mode.Options:

development - Enable debug mode, auto-reload
production - Disable debug, optimize for performance

# Development
FLASK_ENV=development

# Production
FLASK_ENV=production

Never use FLASK_ENV=development in production. It exposes debugging information and is a security risk.

Database Configuration

DB_USER

string

required

MySQL database username.

DB_USER=muebles_user

DB_PASSWORD

string

required

MySQL database password.

DB_PASSWORD=secure_password_here

Use strong passwords in production. Consider using a password manager.

DB_HOST

string

default:"localhost"

MySQL server hostname or IP address.

# Local development
DB_HOST=localhost

# Remote server
DB_HOST=192.168.1.100

# Cloud database
DB_HOST=mysql.example.com

DB_PORT

integer

default:"3306"

MySQL server port.

DB_PORT=3306

DB_NAME

string

required

MySQL database name.

DB_NAME=muebles_roble_db

Security Configuration

SECRET_KEY

string

required

Secret key for session management and CSRF protection.Critical for:

Session encryption
CSRF token generation
Cookie signing

SECRET_KEY=your-very-secure-random-secret-key-here

The application requires SECRET_KEY in production and will raise an error if not set.

Generating a Secure SECRET_KEY

Generate a cryptographically secure key:

import secrets
print(secrets.token_hex(32))

Example output:

9f86d081884c7d659a2feaa0c55ad015a3bf4f1b2b0b822cd15d6c15b0f00a08

Configuration Loading

How Config is Loaded

The application loads configuration in config.py:

config.py

import os
from dotenv import load_dotenv

load_dotenv()

class Config:
    # Database configuration
    DB_USER = os.getenv("DB_USER")
    DB_PASSWORD = os.getenv("DB_PASSWORD")
    DB_HOST = os.getenv("DB_HOST")
    DB_PORT = os.getenv("DB_PORT")
    DB_NAME = os.getenv("DB_NAME")

    # Build database URI
    SQLALCHEMY_DATABASE_URI = (
        f"mysql+pymysql://{DB_USER}:{DB_PASSWORD}@{DB_HOST}:{DB_PORT}/{DB_NAME}"
    )

    SQLALCHEMY_TRACK_MODIFICATIONS = False

    # SECRET_KEY is required for session management and CSRF protection
    SECRET_KEY = os.getenv("SECRET_KEY")
    if not SECRET_KEY:
        # Only allow default in development
        if os.getenv("FLASK_ENV") == "production":
            raise ValueError("SECRET_KEY must be set in production environment")
        SECRET_KEY = "dev-secret-key-change-in-production"

Loading Order

Load .env file

load_dotenv() reads .env file and loads variables

Access with os.getenv()

Variables are accessed using os.getenv("VAR_NAME")

Build config values

Config class builds database URI and other settings

Validate production

Raises error if SECRET_KEY missing in production

Environment-Specific Configurations

Development Environment

.env (development)

FLASK_APP=app.py
FLASK_ENV=development

# Local database
DB_USER=dev_user
DB_PASSWORD=dev_password
DB_HOST=localhost
DB_PORT=3306
DB_NAME=muebles_roble_dev

# Optional in development (auto-generated)
# SECRET_KEY=dev-secret-key

Production Environment

.env (production)

FLASK_APP=app.py
FLASK_ENV=production

# Production database
DB_USER=prod_user
DB_PASSWORD=very_strong_production_password
DB_HOST=prod-mysql-server.example.com
DB_PORT=3306
DB_NAME=muebles_roble_production

# REQUIRED in production
SECRET_KEY=9f86d081884c7d659a2feaa0c55ad015a3bf4f1b2b0b822cd15d6c15b0f00a08

Production checklist:

FLASK_ENV=production
Strong SECRET_KEY set
Strong database password
.env file not committed to version control

Database URI Construction

The database URI is automatically constructed from environment variables:

mysql+pymysql://{DB_USER}:{DB_PASSWORD}@{DB_HOST}:{DB_PORT}/{DB_NAME}

Example URIs

# Development
mysql+pymysql://dev_user:dev_password@localhost:3306/muebles_roble_dev

# Production
mysql+pymysql://prod_user:strong_password@prod-server:3306/muebles_roble_prod

SQLAlchemy Configuration

SQLALCHEMY_DATABASE_URI

Automatically built from database environment variables (see above).

SQLALCHEMY_TRACK_MODIFICATIONS

SQLALCHEMY_TRACK_MODIFICATIONS = False

Disables Flask-SQLAlchemy event system (not needed and saves resources).

Accessing Environment Variables

In Python Code

import os

# Get environment variable
db_user = os.getenv("DB_USER")

# With default value
db_port = os.getenv("DB_PORT", "3306")

# Required variable (raises error if not set)
db_user = os.environ["DB_USER"]

In Application Config

Variables are accessed through the Config class:

from config import Config

app.config.from_object(Config)

# Access in application
db_uri = app.config['SQLALCHEMY_DATABASE_URI']
secret = app.config['SECRET_KEY']

Environment Variable Best Practices

Never commit .env files

Always add .env to .gitignore:

.gitignore

.env
.env.local
.env.*.local

Use .env-template for documentation

Keep .env-template updated with all required variables:

.env-template

FLASK_APP=app.py
FLASK_ENV=development
DB_USER=example_user
# ... all variables with example values

Use strong secrets in production

Generate cryptographically secure keys:

import secrets
secrets.token_hex(32)

Validate required variables

Check for required variables at startup:

if not SECRET_KEY and FLASK_ENV == "production":
    raise ValueError("SECRET_KEY required in production")

Document all variables

Comment your .env-template file:

# Flask application entry point
FLASK_APP=app.py

# Environment: development or production
FLASK_ENV=development

Troubleshooting

Common Issues

SECRET_KEY must be set error

Error: ValueError: SECRET_KEY must be set in production environmentSolution: Add SECRET_KEY to your .env file:

SECRET_KEY=$(python -c "import secrets; print(secrets.token_hex(32))")
echo "SECRET_KEY=$SECRET_KEY" >> .env

Database connection failed

Error: Can’t connect to MySQL serverCheck:

Verify DB_HOST, DB_PORT, DB_USER, DB_PASSWORD in .env
Ensure MySQL is running: sudo systemctl status mysql
Test connection: mysql -h $DB_HOST -u $DB_USER -p
Check firewall rules

Environment variables not loading

Problem: Variables from .env not availableSolutions:

Ensure .env file is in project root
Check file is named exactly .env (not .env.txt)
Verify load_dotenv() is called in config.py
Restart the application

Wrong database selected

Problem: Using wrong database (dev vs prod)Solution: Check FLASK_ENV and DB_NAME:

echo $FLASK_ENV
echo $DB_NAME

Quick Reference

Required Variables

Variable	Required	Default	Description
`DB_USER`	Yes	-	Database username
`DB_PASSWORD`	Yes	-	Database password
`DB_HOST`	Yes	-	Database host
`DB_PORT`	Yes	-	Database port
`DB_NAME`	Yes	-	Database name
`SECRET_KEY`	Prod	dev-key	Secret key for sessions
`FLASK_APP`	No	`app.py`	Application entry point
`FLASK_ENV`	No	`development`	Environment mode

Example .env File

.env

FLASK_APP=app.py
FLASK_ENV=development

DB_USER=muebles_user
DB_PASSWORD=secure_password
DB_HOST=localhost
DB_PORT=3306
DB_NAME=muebles_roble_db

SECRET_KEY=your-secret-key-here

Next Steps

Setup Guide

Complete environment setup instructions

Deployment

Deploy to production

Project Structure

Understand the application architecture

Coding Conventions

Follow best practices

Developer Guide

Templates & Forms

Deployment

​Overview

​Environment File Setup

​Creating the .env File

​Template File

​Configuration Variables

​Flask Configuration

​FLASK_APP

​FLASK_ENV

​Database Configuration

​DB_USER

​DB_PASSWORD

​DB_HOST

​DB_PORT

​DB_NAME

​Security Configuration

​SECRET_KEY

​Generating a Secure SECRET_KEY

​Configuration Loading

​How Config is Loaded

​Loading Order

​Environment-Specific Configurations

​Development Environment

​Production Environment

​Database URI Construction

​Example URIs

​SQLAlchemy Configuration

​SQLALCHEMY_DATABASE_URI

​SQLALCHEMY_TRACK_MODIFICATIONS

​Accessing Environment Variables

​In Python Code

​In Application Config

​Environment Variable Best Practices

​Troubleshooting

​Common Issues

​Quick Reference

​Required Variables

​Example .env File

​Next Steps

Setup Guide

Deployment

Project Structure

Coding Conventions

Build docs developers (and LLMs) love

Overview

Environment File Setup

Creating the .env File

Template File

Configuration Variables

Flask Configuration

FLASK_APP

FLASK_ENV

Database Configuration

DB_USER

DB_PASSWORD

DB_HOST

DB_PORT

DB_NAME

Security Configuration

SECRET_KEY

Generating a Secure SECRET_KEY

Configuration Loading

How Config is Loaded

Loading Order

Environment-Specific Configurations

Development Environment

Production Environment

Database URI Construction

Example URIs

SQLAlchemy Configuration

SQLALCHEMY_DATABASE_URI

SQLALCHEMY_TRACK_MODIFICATIONS

Accessing Environment Variables

In Python Code

In Application Config

Environment Variable Best Practices

Troubleshooting

Common Issues

Quick Reference

Required Variables

Example .env File

Next Steps