FastAPI: High-Performance Python Web Framework for Building APIs

Introduction

FastAPI is a modern, fast, high-performance web framework for building APIs with Python, based on standard Python type hints. It's designed to be easy to learn, fast to code, and ready for production environments.

Key features of FastAPI include:

• Fast: Achieves very high performance, on par with NodeJS and Go, thanks to its foundations in Starlette and Pydantic.
• Fast to code: Significantly increases the speed of feature development.
• Fewer bugs: Helps reduce human-induced errors through strong type checking and validation.
• Intuitive: Offers great editor support with completion everywhere, leading to less debugging time.
• Easy: Designed for ease of use and learning, minimizing time spent reading documentation.
• Robust: Provides production-ready code with automatic interactive documentation.
• Standards-based: Fully compatible with open standards for APIs, including OpenAPI (formerly Swagger) and JSON Schema.

FastAPI stands on the shoulders of giants, leveraging the power of Starlette for its web parts and Pydantic for data handling.

Installation

To get started with FastAPI, it's recommended to use a virtual environment. Once activated, you can install FastAPI along with its standard dependencies using pip:

$ pip install "fastapi[standard]"

Make sure to include fastapi[standard] in quotes to ensure it works correctly across different terminals. This command installs FastAPI, Uvicorn (for serving the application), and other useful tools for development.

Examples

Let's create a simple FastAPI application. Save the following code in a file named main.py:

from typing import Union
from fastapi import FastAPI

app = FastAPI()

@app.get("/")
def read_root():
    return {"Hello": "World"}

@app.get("/items/{item_id}")
def read_item(item_id: int, q: Union[str, None] = None):
    return {"item_id": item_id, "q": q}

To run this application, execute the following command in your terminal:

$ fastapi dev main.py

This will start a development server, typically accessible at http://127.0.0.1:8000. You can then visit http://127.0.0.1:8000/items/5?q=somequery in your browser to see the JSON response.

FastAPI automatically generates interactive API documentation. You can access it at:

• Swagger UI: http://127.0.0.1:8000/docs
• ReDoc: http://127.0.0.1:8000/redoc

Why Use It

FastAPI offers a compelling set of advantages for API development:

• Exceptional Performance: Independent TechEmpower benchmarks consistently show FastAPI applications, running under Uvicorn, as one of the fastest Python frameworks available.
• Developer Productivity: By leveraging Python type hints, FastAPI provides excellent editor support, including auto-completion and type checks, significantly speeding up development and reducing errors.
• Automatic Data Handling: It handles automatic data validation, serialization, and deserialization for various data sources like JSON bodies, path parameters, query parameters, headers, and more. This means less boilerplate code for you.
• Interactive Documentation Out-of-the-Box: With Swagger UI and ReDoc integrated, your API documentation is always up-to-date and interactive, making it easy for other developers to understand and consume your API.
• Robust Ecosystem: Built on Starlette and Pydantic, FastAPI benefits from their stability and extensive features, including WebSockets, CORS, and a powerful Dependency Injection system.
• Industry Adoption: FastAPI is trusted and used by major companies like Microsoft, Uber, and Netflix for their critical services, a testament to its reliability and capabilities.

Links

• Official Documentation: https://fastapi.tiangolo.com
• GitHub Repository: https://github.com/fastapi/fastapi