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How to create an API with FastAPI and Docker

First, create repo that will contain all the files. Then open the repo from VScode.

Create a new python file. In the python file, we can create a simple API like the following:

import uvicorn
from fastapi import FastAPI

app = FastAPI()

inventory = {
    1: {
        "name": "Milk",
        "price": 3.99,
        "brand": "dospinos"
    2: {
        "name": "Milk",
        "price": 4.99,
        "brand": "coronado"

def get_item(item_id: int):
    return inventory[item_id]

# if __name__ == '__main__':
#, host='', port=8000)

Once the file is created, before running the file, I have to create the environment:

pipenv install

Then, let's activate the environment

pipenv shell

Let's check the environment

pipenv --venv

Everything setup, with the last lines of code in the python file with the API we can run it with:


That will serve the API in port 8000. We can go and check if it's running on localhost:8000

If, those lines are not present, we can use the uvicorn package to serve the API:

uvicorn api_example_1:app

Note that there is no .py in the name of the file we want to run.


Now that we have build the API and were able to serve it, we can dockerized.

For this, with the Docker extension in VScode, we can press Fn + F1 to create a file. If the extension throws an error about no connection to daemon socket, we need to aggregate Docker to sudo permissions:

sudo usermod -aG docker ${USER}

I had to restart computer to make this work. After that I was able to use the Docker extension. After opening the options, I look for add docker file and wrote the options asked.

After this, a Docker file was created and also the requirements.txt file to be used during the image build process with venv (I think).

The Docker file looks like the following:

# For more information, please refer to
FROM python:3.10-slim


# Keeps Python from generating .pyc files in the container

# Turns off buffering for easier container logging

# Install pip requirements
COPY requirements.txt .
RUN python -m pip install -r requirements.txt

COPY . /app

# Creates a non-root user with an explicit UID and adds permission to access the /app folder
# For more info, please refer to
RUN adduser -u 5678 --disabled-password --gecos "" appuser && chown -R appuser /app
USER appuser

# During debugging, this entry point will be overridden. For more information, please refer to
CMD ["gunicorn", "--bind", "", "-k", "uvicorn.workers.UvicornWorker", "api_example_1:app"]

Now, the next step is to build the image and run it:

docker built -t test-api .

Then, run the container:

docker run -p 8000:8090 test-api

The instruction will bind the port 8000 on the host with the port 8090 in the container.

Now we can check the container service in localhost:8000