Building REST APIs with FastAPI in Python: A Beginner-Friendly Guide

FastAPI has rapidly become one of the most popular frameworks for building APIs in Python—especially when performance and simplicity matter. It is modern, fast, and developer-friendly, making it a great choice for beginners and professionals alike.

In this blog, we’ll explore what FastAPI is, why developers prefer it, and how you can start building your first REST API.

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What is FastAPI?

FastAPI is a high-performance Python web framework for building APIs quickly and efficiently. It is based on Python type hints and built on top of Starlette (for web handling) and Pydantic (for data validation).

Why FastAPI is popular

Feature	Benefit
Extremely fast	Comparable to Node.js & Go
Auto documentation	Built-in Swagger UI & ReDoc
Type safety with Pydantic	Fewer bugs, easier maintenance
Async support	Ideal for high-concurrency apps
Easy to learn	Minimal code to build APIs

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Installing FastAPI

To install FastAPI and its production server Uvicorn, run:

pip install fastapi
pip install uvicorn

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Creating Your First REST API with FastAPI

Example: A Simple “Hello” API

from fastapi import FastAPI

app = FastAPI()

@app.get("/")
def read_root():
    return {"message": "Hello, FastAPI!"}

Running the Application

uvicorn main:app --reload

Visit in browser:

http://127.0.0.1:8000

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Creating CRUD API with FastAPI

Example: CRUD for Users

from fastapi import FastAPI
from pydantic import BaseModel

app = FastAPI()

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

users_db = []

@app.post("/users")
def create_user(user: User):
    users_db.append(user)
    return user

@app.get("/users")
def get_users():
    return users_db

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Built-In API Documentation

FastAPI automatically generates beautiful documentation:

Type	URL
Swagger UI	http://127.0.0.1:8000/docs
ReDoc	http://127.0.0.1:8000/redoc

This is extremely useful for backend + frontend collaboration.

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When to Use FastAPI

Best Use Cases

✔ High-performance APIs
✔ Microservices
✔ Asynchronous operations (e.g., chats, notifications)
✔ Machine Learning model serving
✔ Scalable backend systems

Not ideal for

❌ Heavy full-stack template rendering frameworks like Django

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FastAPI vs Flask vs Django

Feature	FastAPI	Flask	Django
Performance	⭐⭐⭐⭐⭐	⭐⭐⭐	⭐⭐⭐
Boilerplate	Low	Medium	High
Async support	Yes	Limited	Yes
Built-in Admin	No	No	Yes

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Conclusion

FastAPI is one of the most efficient and modern frameworks available for building RESTful APIs in Python. Its speed, auto documentation, and ease of use make it a perfect choice for beginners, startups, and advanced production systems.

If you haven’t tried FastAPI yet—now is the perfect time! 🚀

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Next Blog Coming Up

👉 Async Programming in Python (AsyncIO)

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