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Building a Python API with FastAPI

Basic API Setup with FastAPI

by Jarrett Retz

March 24th, 2021


    This article in the series will cover setting up a basic FastAPI project. The best tutorial for learning FastAPI is on their website. However, for the sake of continuity, I'll detail some steps here:

    • Setting up a virtual environment
    • Downloading necessary modules
    • Creating project files
    • Inserting starter code

    Virtual Environment

    First, create a new directory. Or, you can navigate (in a terminal or command shell) to the directory where you wish to create the project.

    I made a directory called fastapi_tutorial.

    Next, if you don't have it downloaded already, download virtualenv.

    $ pip3 install virtualenv

    This should install the package into your global Python interpreter or your current activated environment.

    Now, we can create a new virtual environment for the project.

    Why Create a Virtual Environment?

    We need a separate virtual environment for the project so that when we deploy, we know the minimum number of modules that are required to build the API.

    Creating a new environment will allow us to use the command pip freeze later to easily grab or package names and version.

    In the terminal run the command:

    $ virtualenv venv

    After the command is done, a new virtual environment folder is added to our project folder. The name of our new environment is venv.

    Finally, we need to activate the environment with:

    $ source venv/bin/activate

    Install Packages

    Next, we need to install the packages necessary to run FastAPI locally.

    $ pip3 install fastapi uvicorn

    The uvicorn package is for running the local server. Additionally, installing fastapi installed:

    • pydantic
    • starlette
    • typing-extensions

    Create the Server File

    Inside the root of the project, create the file Paste the below code into the file:

    from fastapi import FastAPI
    app = FastAPI()
    async def root():
        return {"message": "Hello World"}

    In this file, we create our API and store it in the app variable.

    The "/" route is the index of our API. We add this route as the only route available. If you visit this route, you'll receive the return value, {"message": "Hello World"}.

    Start the Server

    With the virtual environment active, we can start the development server to run locally.

    In the terminal, in the root directory, run the command:

    uvicorn main:app --reload

    You'll see some output and the line:

    Uvicorn running on (Press CTRL+C to quit)

    Open up a browser and enter http://localhost:8000 for the URL.

    You should see our return value, {"message":"Hello World"}, and that means that we are successful!

    In the next article, we'll explore FastAPI more and build out the information for our routes. Thanks for reading!

    Jarrett Retz

    Jarrett Retz is a freelance web application developer and blogger based out of Spokane, WA.

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