FastAPI Basics

Introduction

from fastapi import FastAPI
 
app = FastAPI()
 
@app.get("/")
async def root():
	return {"message": "Hello World"}

• *FastAPI is a Python class that provides all the functionality for our API
• The @app.get("/)is a path operation decorator (A decorator takes the function below and does something with it)
• In the above example,
  • path: is /
  • operation: is get
  • function: is the function below the “decorator”

Technical Details

FastAPI is a class that inherits directly from Starlette
Starlette is a lightweight ASGI framework/toolkit, which is ideal for building async web services in Python
ASGI (Asynchronous Server Gateway Interface) is a spiritual successor to WSGI(Web Server Gateway Interface), intended to provide a standard interface between async-capable Python web servers, frameworks, and applications.

Common HTTP methods : POST: to create data GET: to read data PUT: to update data DELETE: to delte data

Dependencies

FastAPI has a very powerful and intuitive Dependency Injection system

• Dependency Injection means, in programming, that there is a way for our code (in our reference, the path operation functions) to declare things that it requires to work and use: “dependencies”
• And then, the system (FastAPI) will take care of doing whatever is needed to provide our code with those dependencies (“inject” the dependencies)
• Useful when we need to:
  • Have shared logic (Minimizes code repetition)
  • Share database connections
  • Enforce security, authentication, role requirements, etc.
• Any python Callable (Python class or function) can be declared as a Dependency

from fastapi import Depends,FastAPI #Imports Depends

Dependencies with yield

• Dependencies can do some extra steps after finishing
• To do this, we use yield, and write the extra steps (code) after
• We can use yield one single time pr dependency

asynd def get_db():
	db = DBSession()
	try:
		yield db
	finally:
		db.close()

In the above code, only the code prior to and including the yield statement will execute before creating a response (The yielded value is what is injected into path operations and other dependencies)

• The code following the yield statement is executed after creating the response but before sending it