PART IV · BACKEND

FastAPI

A Python web framework commonly used to build APIs.

What is it?

FastAPI is a Python framework for building HTTP APIs.

It provides tools for defining routes, receiving requests, validating data, and returning responses.

Simple Definition：
FastAPI helps developers build APIs with Python.

Python is the language.

FastAPI provides the API-building structure.

Python→FastAPI→API Routes→Backend

FastAPI can help:

FastAPI is used for:

from fastapi import FastAPI

app = FastAPI()

@app.get("/orders/{order_id}")
def get_order(order_id: int):
    return {"id": order_id}

The route connects an HTTP GET request with a Python function.

HTTP Request→FastAPI→Route→Python Function→Business Logic→Response

A framework used to build APIs.

The interface exposed to other systems.

FastAPI ≠ API

ENGLISH TERM	中文	SIMPLE ENGLISH	中文小白理解
FastAPI	FastAPI	A Python framework used to build HTTP APIs.	用 Python 快速开发 HTTP API 的后端框架。
API	应用程序接口	An interface used by software systems to communicate.	不同软件系统之间进行通信的接口。
Route	路由	A mapping between a URL and backend code.	把 URL 请求对应到某段后端处理代码的规则。
Decorator	装饰器	Python syntax used by FastAPI to attach behavior to functions.	FastAPI 常用来把 HTTP 路由绑定到 Python 函数的语法形式。
Request Validation	请求校验	Checking incoming data before processing it.	后端处理请求前检查传入数据是否合法。
OpenAPI	OpenAPI 规范	A standard format used to describe APIs.	FastAPI 可以自动生成的 API 标准描述格式。

FastAPI is a Python framework.

It connects HTTP routes to Python functions.

It can validate request data and generate API documentation.