Getting started with FastAPI and Docker

Joachim Watkidog — Sun, 14 Nov 2021 10:47:26 +0000

In this beginner’s guide, I will take you through the basic steps to get your first application running using FastAPI and Docker.

Table of contents

FastAPI
Docker
Building a FastAPI application with Docker

FastAPI

FastAPI is a fast, modern, high performance, open source Python web framework used to build APIs with Python 3.6+. It is a minimalistic framework and quite new with a smaller community compared to Django and Flask but when it comes to performance, it is the fastest by far. It supports asynchronous programming, which is a plus. To learn more about fastAPI, visit their official docs here

Docker

Docker is a containerization platform. It enables you to build, run and ship your application, packages your code and all its dependencies enabling your application to run consistently across different computing environments.

A container is a virtualized environment for running an application. It includes everything needed for an application to run.

Docker uses the client-server architecture. The client component communicates with the server (the Docker Engine) using a RESTful API. The Docker Engine builds and runs the Docker containers.

Building your first FastAPI and Docker application

In this section, we are going to dockerize a simple python application.

Requirements

Linux or Mac computer. You can also use Windows but some commands are different.
Python 3.6+

We shall start by installing a virtual environment in which we will create our application.

Install a virtual environment - virtualenv

pip3 install virtualenv

Navigate to a directory of choice and create the virtual environment.

python3 -m virtualenv hello-app-env

Activate the virtual environment

source hello-app-env/bin/activate

Change directory into the virtual environment created and install fasAPI and uvicorn. We'll use uvicorn to run our application.

pip3 install fastapi uvicorn

Create a requirements.txt file. This lists all the packages required by our application.

pip3 freeze > requirements.txt

Now that we are all set up. Let's create a python file main.py in your src directory and add the following code:
/src/main.py

from fastapi import FastAPI

app = fastAPI()

@app.get("/")
def index():
    return {"Greeting": "Hello World!"}

Note: use @app.post() if you're accepting sensitive data from the user like usernames and passwords.

Create a Docker file called Dockerfile

FROM python:3.9

COPY ./src /app/src
COPY requirements.txt /app

WORKDIR /app

RUN pip3 install -r requirements.txt

EXPOSE 8000

CMD ["uvicorn", "main:app", "--host=0.0.0.0", "--reload"]

Note: --reload will automatically update changes when made so you won't have to re-run the container.

To build your Docker image, open your terminal and enter:

docker build -t hello-world-env .

Run the docker image

docker run -p 8000:8000 --name hello-app hello-world-env

Note: In this case, hello-app is the name I'm giving to the container, hello-world-env is the image

To verify that the image and container exist, run these commands in your terminal. The directory you are in does not matter:

docker image ls

docker container ls

The docker run command will spin up your local server and you can view your results through this URL http://localhost:8000 or http://127.0.0.1:8000 ``

Conclusion