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FastAPI

High-performance Python framework for building APIs with standard type hints — fast to code and ready for production.

Overview​

FastAPI is a modern, high-performance web framework for building APIs with Python 3.8+ based on standard Python type hints. It is designed to be easy to use and learn, while providing production-ready performance on par with NodeJS and Go. By leveraging Starlette for the web parts and Pydantic for the data parts, FastAPI ensures that your code is both fast to execute and fast to write.

The framework's core philosophy is to minimize code duplication and maximize developer productivity. It provides automatic interactive API documentation (Swagger UI and ReDoc) based on the OpenAPI standard, allowing you to test your endpoints directly from the browser. With its robust type-checking and validation system, FastAPI helps you catch bugs early in the development cycle, leading to more stable and maintainable applications.

FastAPI stands on the shoulders of giants, being fully compatible with (and based on) the open standards for APIs: OpenAPI and JSON Schema. This compatibility enables a vast ecosystem of tools, including automatic client code generation for many programming languages. Whether you are building a simple prototype or a complex enterprise system, FastAPI provides the tools and performance needed to succeed.

Key Concepts​

  • The FastAPI Application The FastAPI Application Class: The central object used to configure your API, manage application state, and register routes.
  • Path Operations Defining HTTP Path Operations: Functions decorated with HTTP methods that define how your API responds to specific URL paths.
  • Dependency Injection Dependency Injection: A powerful engine for sharing logic, managing database sessions, and enforcing security across your endpoints.
  • Data Schemas & Validation Data Schemas and Validation: Uses Pydantic to automatically validate incoming request bodies and serialize outgoing response data.
  • Security & Authentication Security & Authentication: Built-in support for complex security requirements, including OAuth2 with scopes and JWT tokens.
  • Routing System Routing System: Allows you to modularize your application into reusable components and sub-routers for better organization.

Common Use Cases​

  • Building high-performance RESTful APIs for web, mobile, and IoT applications.
  • Developing microservices with low latency and high concurrency requirements.
  • Creating machine learning model serving endpoints with automatic input validation.
  • Implementing real-time features using WebSockets and Server-Sent Events.
  • Building secure backends with integrated OAuth2 and OpenID Connect authentication.

Getting Started​

To begin your journey with FastAPI, head over to the Getting Started section to set up your environment and create your first API. Once you're comfortable with the basics, explore Request Data & Parameters to learn how to handle user input, or dive into Dependency Injection to start building modular and testable code.