Creating Our First App Using FastAPI

Get started with creating your first app using FastAPI.

We'll cover the following

Creating a simple FastAPI app

Let’s now create a basic FastAPI application.

from fastapi import FastAPI

app = FastAPI()

@app.get("/")
def root():
  return {"message": "Hello World"}
Simple app using FastAPI

Explanation

To learn how to execute the FastAPI application on your local machine, refer to the Appendix section.

  • In line 1, we import the FastAPI, which is a Python class that provides all the functionality for the API.

  • In line 3, we create an instance of the class FastAPI and name it app. This app is the same one called by uvicorn in the above terminal.

  • In line 5, we create a GET path/route. This is the default route or the route after /. For example, in a URL like https://example.com/items/foo, the path would be /items/foo.

  • In line 6, we define the function that will be executed whenever someone visits the above-mentioned route.

  • In line 7, we finally return a response to the client whenever this route is accessed.

Points to remember

  • If we create our app like this:

    my_awesome_api = FastAPI()

    And put it in a file main.py, then you would call uvicorn like this:

    uvicorn main:my_awesome_api --reload

  • We can also use the other operations instead of GET:

    • @app.post() can be used if we want the client application to access the route in a POST manner.
    • @app.put() can be used if we want the client application to access the route in a PUT manner.
    • @app.delete() can be used if we want the client application to access the route in a DELETE manner.

    There are four more operation types that could also be used. They are @app.options(), @app.head(), @app.patch(), and @app.trace().