In this post we will run through setting up a virtual environment, install FastAPI and write a simple script to test the installation.

Setup a virtual environment

Before starting any new project make sure you create and use a virtual environment. Follow these steps

# create a new directory
mkdir install-fastapi
cd install-fastapi

# create the virtual environment
python -m venv .venv

# activate the virtual environment
. .venv/bin/activate # macos/linux
.venv/Scripts/Activate.bat # windows

Once activated, you’ll notice that the command prompt changes to indicate you’re now inside the virtual environment.

Installing FastAPI

There are two main ways to install FastAPI:

  1. standard: automatically installs some additional dependencies.
  2. non-standard: just installs FastAPI without the additional dependencies.

I would recommend standard, as this avoids having to install other libraries later on and also avoids unnecessary bugs and things not working.

# standard install
pip install "fastapi[standard]"

# non-standard install
pip install fastapi

Testing the FastAPI Installation

Assuming you don’t see any pip errors FastAPI and all the additional dependencies should be installed. Finally, we should check to make sure everything works. Below is a simple API which tests the basic operation. Create a new file called api.py with the following contents:

from fastapi import FastAPI

app = FastAPI()

@app.get("/")
async def root():
  return {"message": "Success!"}

Now, let’s run the script in development mode:

fastapi dev api.py

Again, assuming you don’t see any error messages you should get an output looking like this:

INFO     Using path api.py
INFO     Resolved absolute path /Users/jwfranklin/dev/mdev/tmp/install-fastapi/api.py
INFO     Searching for package file structure from directories with __init__.py files
INFO     Importing from /Users/jwfranklin/dev/mdev/tmp/install-fastapi

 ╭─ Python module file ─╮
 │                      │
 │  🐍 api.py           │
 │                      │
 ╰──────────────────────╯

INFO     Importing module api
INFO     Found importable FastAPI app

 ╭─ Importable FastAPI app ─╮
 │                          │
 │  from api import app     │
 │                          │
 ╰──────────────────────────╯

INFO     Using import string api:app

 ╭────────── FastAPI CLI - Development mode ───────────╮
 │                                                     │
 │  Serving at: http://127.0.0.1:8000                  │
 │                                                     │
 │  API docs: http://127.0.0.1:8000/docs               │
 │                                                     │
 │  Running in development mode, for production use:   │
 │                                                     │
 │  fastapi run                                        │
 │                                                     │
 ╰─────────────────────────────────────────────────────╯

INFO:     Will watch for changes in these directories: ['/Users/jwfranklin/dev/mdev/tmp/install-fastapi']
INFO:     Uvicorn running on http://127.0.0.1:8000 (Press CTRL+C to quit)
INFO:     Started reloader process [61773] using WatchFiles
INFO:     Started server process [61824]
INFO:     Waiting for application startup.
INFO:     Application startup complete.

Towards the end of the output is a locally accessible web address. Run the following command in a new terminal window:

curl http://127.0.0.1:8000

You should see the following, showing that everything has worked successfully:

{"message":"Success!"}%