Tools in Data Science

REST APIs#

REST (Representational State Transfer) APIs are the standard way to build web services that allow different systems to communicate over HTTP. They use standard HTTP methods and JSON for data exchange.

Watch this comprehensive introduction to REST APIs (52 min):

Key Concepts:

HTTP Methods
- GET: Retrieve data
- POST: Create new data
- PUT/PATCH: Update existing data
- DELETE: Remove data
Status Codes
- 2xx: Success (200 OK, 201 Created)
- 4xx: Client errors (400 Bad Request, 404 Not Found)
- 5xx: Server errors (500 Internal Server Error)

Here’s a minimal REST API using FastAPI. Run this server.py script via uv run server.py:

# /// script
# requires-python = ">=3.13"
# dependencies = [
#     "fastapi",
#     "uvicorn",
# ]
# ///
from fastapi import FastAPI, HTTPException
from typing import Dict, List

app = FastAPI()

# Create a list of items that will act like a database
items: List[Dict[str, float | int | str]] = []


# Create a GET endpoint that returns all items
@app.get("/items")
async def get_items() -> List[Dict[str, float | int | str]]:
    return items


# Create a GET endpoint that returns a specific item by ID
@app.get("/items/{item_id}")
async def get_item(item_id: int) -> Dict[str, float | int | str]:
    if item := next((i for i in items if i["id"] == item_id), None):
        return item
    raise HTTPException(status_code=404, detail="Item not found")


# Create a POST endpoint that creates a new item
@app.post("/items")
async def create_item(item: Dict[str, float | str]) -> Dict[str, float | int | str]:
    new_item = {"id": len(items) + 1, "name": item["name"], "price": float(item["price"])}
    items.append(new_item)
    return new_item


if __name__ == "__main__":
    import uvicorn

    uvicorn.run(app, host="0.0.0.0", port=8000)

Test the API with curl:

# Get all items
curl http://localhost:8000/items

# Create an item
curl -X POST http://localhost:8000/items \
  -H "Content-Type: application/json" \
  -d '{"name": "Book", "price": 29.99}'

# Get specific item
curl http://localhost:8000/items/1

Best Practices:

Use Nouns for Resources
- Good: /users, /posts
- Bad: /getUsers, /createPost
Version Your API
```
/api/v1/users
/api/v2/users
```

Handle Errors Consistently

{"error": "Not Found", "message": "User 123 not found", "status_code": 404}

Use Query Parameters for Filtering

/api/posts?status=published&category=tech

Implement Pagination
```
/api/posts?page=2&limit=10
```

Tools:

Postman: API testing and documentation
Swagger/OpenAPI: API documentation
HTTPie: Modern command-line HTTP client
JSON Schema: API request/response validation

Learn more about REST APIs: