Building APIs with FastAPI

Key Concepts

When building APIs with FastAPI, it's essential to understand the following key concepts:

• Endpoints: The specific URLs where your API can be accessed.
• Request Methods: The HTTP methods (GET, POST, PUT, DELETE) used to interact with your API.
• Path Parameters and Query Parameters: Variables in the URL and query string that provide additional context to your API.

1. Endpoints

Endpoints are the specific URLs where your API can be accessed. Each endpoint corresponds to a different functionality or resource in your API. For example, you might have an endpoint to retrieve a list of users and another to create a new user.

Here is an example of defining endpoints in FastAPI:

from fastapi import FastAPI

app = FastAPI()

@app.get("/users")
def get_users():
    return {"message": "List of users"}

@app.post("/users")
def create_user():
    return {"message": "User created"}
    

2. Request Methods

Request methods define the type of action you want to perform on a resource. The most common methods are GET (retrieve data), POST (create data), PUT (update data), and DELETE (remove data).

Here is an example of using different request methods in FastAPI:

from fastapi import FastAPI

app = FastAPI()

@app.get("/items/{item_id}")
def read_item(item_id: int):
    return {"item_id": item_id}

@app.post("/items/")
def create_item(item: dict):
    return {"item": item}

@app.put("/items/{item_id}")
def update_item(item_id: int, item: dict):
    return {"item_id": item_id, "updated_item": item}

@app.delete("/items/{item_id}")
def delete_item(item_id: int):
    return {"message": f"Item {item_id} deleted"}
    

3. Path Parameters and Query Parameters

Path parameters are variables in the URL path that are used to identify a specific resource. Query parameters, on the other hand, are used to filter or provide additional context to the request.

Here is an example of using path and query parameters in FastAPI:

from fastapi import FastAPI

app = FastAPI()

@app.get("/items/{item_id}")
def read_item(item_id: int, q: str = None):
    return {"item_id": item_id, "query": q}
    

In this example, item_id is a path parameter that identifies the item, and q is a query parameter that provides additional context or filtering options.

Analogies

Think of building an API with FastAPI as creating a menu for a restaurant. Each endpoint is a dish on the menu, and the request methods are the actions you can take with each dish (order, modify, cancel). Path parameters are like the dish name, and query parameters are like the special instructions you give to the chef.

By understanding these key concepts, you can effectively build and manage APIs with FastAPI, providing a robust and user-friendly interface for your applications.