Creating a Basic RESTful API with FastAPI in Python

In this tutorial, we will go through the process of building a simple REST API using FastAPI in Python. FastAPI is a modern web framework for building APIs with Python 3.6+ based on standard Python type hints. It is fast, easy to use, and highly efficient. We will create a simple API with basic CRUD operations for a fictional "todo" application.

Step 1: Setting up the Environment

First, make sure you have Python installed on your machine. You can download and install Python from the official website (https://www.python.org/). Next, create a new directory for your project and navigate to it in your terminal.

To create a new virtual environment, run the following command:

python -m venv env

Activate the virtual environment by running the appropriate command for your operating system:

For Windows:

.envScriptsactivate

For MacOS/Linux:

source env/bin/activate

Install FastAPI and Uvicorn (ASGI server) using pip:

pip install fastapi uvicorn

Step 2: Creating the API

Create a new Python file, for example, main.py, and import necessary modules:

from fastapi import FastAPI
from pydantic import BaseModel

app = FastAPI()

Define the data model for a todo item using Pydantic:

class TodoItem(BaseModel):
    id: int
    title: str
    description: str
    done: bool

Now, let’s create a list to store todo items:

todo_list = []

Create API routes for CRUD operations:

@app.get("/todos")
def get_all_todos():
    return todo_list

@app.get("/todos/{todo_id}")
def get_todo(todo_id: int):
    for todo in todo_list:
        if todo["id"] == todo_id:
            return todo
    return {"error": "Todo not found"}

@app.post("/todos")
def create_todo(todo: TodoItem):
    todo_dict = todo.dict()
    todo_list.append(todo_dict)
    return todo_dict

@app.put("/todos/{todo_id}")
def update_todo(todo_id: int, todo: TodoItem):
    for index, item in enumerate(todo_list):
        if item["id"] == todo_id:
            todo_list[index] = todo.dict()
            return {"message": "Todo updated"}
    return {"error": "Todo not found"}

@app.delete("/todos/{todo_id}")
def delete_todo(todo_id: int):
    for index, item in enumerate(todo_list):
        if item["id"] == todo_id:
            del todo_list[index]
            return {"message": "Todo deleted"}
    return {"error": "Todo not found"}

Step 3: Running the API

To run the API, use the following command:

uvicorn main:app --reload

You can now access the API endpoints on http://localhost:8000/docs to interact with the API using the Swagger UI. You can test the CRUD operations for todo items by sending requests to the appropriate endpoints.

That’s it! You have successfully built a simple REST API using FastAPI in Python. FastAPI makes it easy to create APIs with Python, providing built-in validation, automatic documentation generation, and high performance. There are many more features and capabilities of FastAPI that you can explore to build complex APIs for your applications.