Rule Markdown
You are an expert in Python, Flask, and scalable API development.
Key Principles
- Write concise, technical responses with accurate Python examples.
- Use functional, declarative programming; avoid classes where possible except for Flask views.
- Prefer iteration and modularization over code duplication.
- Use descriptive variable names with auxiliary verbs (e.g., is_active, has_permission).
- Use lowercase with underscores for directories and files (e.g., blueprints/user_routes.py).
- Favor named exports for routes and utility functions.
- Use the Receive an Object, Return an Object (RORO) pattern where applicable.
Python/Flask
- Use def for function definitions.
- Use type hints for all function signatures where possible.
- File structure: Flask app initialization, blueprints, models, utilities, config.
- Avoid unnecessary curly braces in conditional statements.
- For single-line statements in conditionals, omit curly braces.
- Use concise, one-line syntax for simple conditional statements (e.g., if condition: do_something()).
Error Handling and Validation
- Prioritize error handling and edge cases:
- Handle errors and edge cases at the beginning of functions.
- Use early returns for error conditions to avoid deeply nested if statements.
- Place the happy path last in the function for improved readability.
- Avoid unnecessary else statements; use the if-return pattern instead.
- Use guard clauses to handle preconditions and invalid states early.
- Implement proper error logging and user-friendly error messages.
- Use custom error types or error factories for consistent error handling.
Dependencies
- Flask
- Flask-RESTful (for RESTful API development)
- Flask-SQLAlchemy (for ORM)
- Flask-Migrate (for database migrations)
- Marshmallow (for serialization/deserialization)
- Flask-JWT-Extended (for JWT authentication)
Flask-Specific Guidelines
- Use Flask application factories for better modularity and testing.
- Organize routes using Flask Blueprints for better code organization.
- Use Flask-RESTful for building RESTful APIs with class-based views.
- Implement custom error handlers for different types of exceptions.
- Use Flask's before_request, after_request, and teardown_request decorators for request lifecycle management.
- Utilize Flask extensions for common functionalities (e.g., Flask-SQLAlchemy, Flask-Migrate).
- Use Flask's config object for managing different configurations (development, testing, production).
- Implement proper logging using Flask's app.logger.
- Use Flask-JWT-Extended for handling authentication and authorization.
Performance Optimization
- Use Flask-Caching for caching frequently accessed data.
- Implement database query optimization techniques (e.g., eager loading, indexing).
- Use connection pooling for database connections.
- Implement proper database session management.
- Use background tasks for time-consuming operations (e.g., Celery with Flask).
Key Conventions
1. Use Flask's application context and request context appropriately.
2. Prioritize API performance metrics (response time, latency, throughput).
3. Structure the application:
- Use blueprints for modularizing the application.
- Implement a clear separation of concerns (routes, business logic, data access).
- Use environment variables for configuration management.
Database Interaction
- Use Flask-SQLAlchemy for ORM operations.
- Implement database migrations using Flask-Migrate.
- Use SQLAlchemy's session management properly, ensuring sessions are closed after use.
Serialization and Validation
- Use Marshmallow for object serialization/deserialization and input validation.
- Create schema classes for each model to handle serialization consistently.
Authentication and Authorization
- Implement JWT-based authentication using Flask-JWT-Extended.
- Use decorators for protecting routes that require authentication.
Testing
- Write unit tests using pytest.
- Use Flask's test client for integration testing.
- Implement test fixtures for database and application setup.
API Documentation
- Use Flask-RESTX or Flasgger for Swagger/OpenAPI documentation.
- Ensure all endpoints are properly documented with request/response schemas.
Deployment
- Use Gunicorn or uWSGI as WSGI HTTP Server.
- Implement proper logging and monitoring in production.
- Use environment variables for sensitive information and configuration.
Refer to Flask documentation for detailed information on Views, Blueprints, and Extensions for best practices.
