What is FastAPI?

FastAPI is a modern, high-performance web framework for building APIs with Python 3.7+. It’s especially popular in the machine learning and data science world for quickly creating RESTful APIs to serve ML models, but it’s powerful enough for any web backend.

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Key Features of FastAPI

1. Blazing Fast Performance
   • Built on Starlette and Pydantic under the hood.
   • Comparable to Node.js and Go in speed—one of the fastest Python frameworks.
2. Automatic Interactive Documentation
   • Generates OpenAPI (Swagger UI) and ReDoc docs automatically for your API.
   • Just run your server and visit /docs or /redoc—no extra setup.
3. Type Hints and Validation
   • Uses Python type hints for data validation, serialization, and auto-complete in editors.
   • Data models are defined using Pydantic, providing powerful request/response parsing.
4. Easy to Use
   • Simple, intuitive syntax—great for rapid prototyping and production-grade APIs.
   • Minimal boilerplate compared to Flask or Django.
5. Asynchronous Support
   • First-class support for Python async and await for handling large numbers of concurrent requests.
6. Dependency Injection
   • Robust dependency injection system for authentication, database, or shared services.
7. Production Ready
   • Designed for building scalable APIs used in production (used by companies like Uber, Microsoft, Netflix).

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Basic Example: FastAPI ML Model Serving

from fastapi import FastAPI
from pydantic import BaseModel

app = FastAPI()

class InputData(BaseModel):
    text: str

@app.post("/predict")
def predict(data: InputData):
    # Imagine loading and using your ML model here
    result = {"prediction": data.text.upper()}
    return result

• Run with:
  uvicorn myapp:app --reload
• Docs:
  http://localhost:8000/docs

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When to Use FastAPI

• Serving machine learning models (REST/gRPC API).
• Backend for web or mobile apps.
• Microservices in a cloud/Kubernetes environment.
• APIs needing automatic validation/documentation.
• Projects that require async performance.

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FastAPI vs. Flask/Django

Feature	FastAPI	Flask	Django
Type Safety	Excellent	Limited	Limited
Async Support	Excellent	Poor	Moderate
Auto Docs	Yes	No	No
Performance	High	Moderate	Moderate
Learning Curve	Easy	Very Easy	Steep
Best Use	APIs	APIs/Web	Full Web

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Summary

FastAPI is one of the fastest, easiest ways to build robust APIs in Python, with automatic docs, validation, async support, and great developer experience—making it perfect for machine learning, microservices, or any modern web backend.

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