Tutorial 2023: Creating Your First API with FastAPI in Python

Creating your very first API with FastAPI in Python is a great way to get started with web development and building modern, efficient web applications. FastAPI is a fast (high-performance), easy to use, and flexible web framework for building APIs with Python. In this tutorial, we will go through the step-by-step process of creating your very first API with FastAPI in Python.

Before we get started, make sure you have Python installed on your computer. You can download and install Python from the official Python website. Once you have Python installed, you will also need to install FastAPI and Uvicorn, which is a lightning-fast ASGI server implementation, using pip, the package manager for Python. You can install FastAPI and Uvicorn by running the following commands in your terminal:

pip install fastapi
pip install uvicorn

Now that you have FastAPI and Uvicorn installed, let’s create our very first API with FastAPI in Python. First, create a new Python file called app.py. In this file, we will define our FastAPI application and create our API endpoints.

from fastapi import FastAPI

app = FastAPI()

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

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

In the code above, we first import the FastAPI class from the fastapi module, and then create a new instance of FastAPI called app. We then define two API endpoints using the @app.get decorator. The read_root function returns a simple JSON response with a message "Hello, World!", while the read_item function expects an item_id parameter and an optional q query parameter, and returns a JSON response with the values of these parameters.

Next, we need to run our FastAPI application using the Uvicorn server. To do this, open your terminal and run the following command:

uvicorn app:app --reload

This command tells Uvicorn to run the FastAPI application defined in the app.py file with automatic code reloading enabled. Once the server is running, you should see output similar to the following:

INFO:     Uvicorn running on http://127.0.0.1:8000 (Press CTRL+C to quit)
INFO:     Started reloader process [12345]
INFO:     Started server process [12346]
INFO:     Waiting for application startup.
INFO:     Application startup complete.

Now, open your web browser and navigate to http://127.0.0.1:8000/. You should see a JSON response with the message "Hello, World!". You can also try accessing different endpoints, such as http://127.0.0.1:8000/items/1 with or without a query parameter to test the read_item endpoint.

Congratulations! You have successfully created your very first API with FastAPI in Python. You can now build upon this example to create more complex APIs with FastAPI and explore its many features and capabilities. Happy coding!