Python API Development — REST APIs with FastAPI

FastAPI is the modern Python framework for building APIs. It is fast, easy to learn, and production-ready.

Learning Objectives

• Build REST APIs with FastAPI
• Validate data with Pydantic models
• Add authentication and middleware
• Deploy APIs with uvicorn

Basic FastAPI App

from fastapi import FastAPI
from pydantic import BaseModel

app = FastAPI()

class User(BaseModel):
    name: str
    email: str
    age: int

users = []

@app.get("/")
def root():
    return {"message": "Welcome to the API"}

@app.post("/users")
def create_user(user: User):
    users.append(user)
    return {"status": "created", "user": user}

@app.get("/users/{user_id}")
def get_user(user_id: int):
    if user_id < len(users):
        return users[user_id]
    return {"error": "User not found"}

@app.get("/search")
def search(q: str = "", limit: int = 10):
    return {"query": q, "limit": limit}

Running the API

# Install
pip install fastapi uvicorn

# Run
uvicorn main:app --reload

# Docs at http://localhost:8000/docs

Key Takeaways

1. FastAPI auto-generates API documentation
2. Use Pydantic for request/response validation
3. Path parameters use {} syntax
4. Query parameters are function arguments
5. Use --reload for development