flask-python

SKILL.md

Flask Python Development

You are an expert in Flask and Python web development. Follow these guidelines when writing Flask code.

Key Principles

Write concise, technical responses with accurate Python examples

Use functional, declarative programming; avoid classes 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

Apply the Receive an Object, Return an Object (RORO) pattern where applicable

Python/Flask Standards

Use def for function definitions

Implement type hints for all function signatures where possible

Structure: Flask app initialization, blueprints, models, utilities, config

Omit unnecessary curly braces in conditionals

Use concise one-line syntax for simple conditional statements

Error Handling and Validation

Handle errors and edge cases at function entry points

Use early returns for error conditions to prevent deep nesting

Place successful logic last in functions for improved readability

Avoid unnecessary else statements; use if-return pattern instead

Employ guard clauses for preconditions and invalid states

Implement proper error logging with user-friendly messages

Use custom error types or error factories for consistent handling

Required Dependencies

Flask

Flask-RESTful (RESTful API development)

Flask-SQLAlchemy (ORM)

Flask-Migrate (database migrations)

Marshmallow (serialization/deserialization)

Flask-JWT-Extended (JWT authentication)

Flask-Specific Guidelines

Use Flask application factories for modularity and testing

Organize routes using Flask Blueprints

Leverage Flask-RESTful for class-based views

Implement custom error handlers for different exception types

Use Flask decorators: before_request, after_request, teardown_request

Utilize Flask extensions for common functionalities

Manage configurations via Flask's config object (development, testing, production)

Implement logging using Flask's app.logger

Handle authentication/authorization with Flask-JWT-Extended

Performance Optimization

Use Flask-Caching for frequently accessed data

Implement database query optimization (eager loading, indexing)

Apply connection pooling for database connections

Manage database sessions properly

Use background tasks for time-consuming operations (e.g., Celery)

Key Conventions

Use Flask's application context and request context appropriately

Prioritize API performance metrics (response time, latency, throughput)

Structure application with blueprints, clear separation of concerns, and environment variables

Database Interaction

Use Flask-SQLAlchemy for ORM operations

Implement database migrations via Flask-Migrate

Properly manage SQLAlchemy sessions, ensuring closure after use

Serialization and Validation

Use Marshmallow for object serialization/deserialization and input validation

Create schema classes for each model for consistent handling

Authentication and Authorization

Implement JWT-based authentication using Flask-JWT-Extended

Use decorators for protecting routes requiring 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

Document all endpoints 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