Fast API

Mainly notes for myself to not forget

FastAPI is a modern, high-performance web framework for building APIs with Python 3.7+ that is designed with RESTful principles in mind (REST API) Source: https://fastapi.tiangolo.com/tutorial/first-steps/

Operations

GET

• Used to define an endpoint that handles HTTP GET requests

from fastapi import FastAPI
 
app = FastAPI()
 
#this is a decorator
@app.get("/")
def read_root():
    return {"message": "Hello World"}
 
@app.get("/items/{item_id}")
def read_item(item_id: int, q: str = None):
    return {"item_id": item_id, "q": q}

• When a client (such as a web browser or another application) sends an HTTP GET request to a FastAPI endpoint, the server processes the request, executes the corresponding handler function, and returns the response to the client.
• read_root()
  • When you open your browser and navigate to the root URL of your FastAPI server, it will return a JSON response {"message": "Hello World"}.

POST

app = FastAPI()
 
@app.post("/items/")
async def create_item(item: dict):
    return item

Middleware

• A “middleware” is a function that works with every request before it is processed by any specific path operation. And also with every response before returning it.
• Not mandatory, but highly recommended and often necessary
• It enhances functionality by providing mechanisms for logging, authentication, validation, error handling, etc
• https://fastapi.tiangolo.com/tutorial/middleware/?h=middleware

import time
 
from fastapi import FastAPI, Request
 
app = FastAPI()
 
 
@app.middleware("http")
async def add_process_time_header(request: Request, call_next):
    start_time = time.time() #can add code before and after handling the request
    
    response = await call_next(request)
    
    process_time = time.time() - start_time
    response.headers["X-Process-Time"] = str(process_time)
    return response

CORSMiddleware

• If your FastAPI backend and Vite frontend are running on different ports (or domains), you need to enable CORS on your backend to allow requests from your frontend.
• For example, if your backend is running on http://127.0.0.1:8000 and your frontend (Vite) is running on http://127.0.0.1:3000, they are considered different origins, and CORS needs to be configured.
• https://fastapi.tiangolo.com/tutorial/cors/