Docker Hands-on: Learn Dockerfile, Container, Port Forwarding with Sample Flask Project

This tutorial demonstrates building and deploying a simple Flask application using Docker. We'll cover creating a Dockerfile, building the image, running a container, and even pushing the image to Docker Hub. For those unfamiliar with Docker fundamentals, check out this previous post:

• Docker Tutorial

Let's get started with a hands-on example:

Project Setup:

1. Create a directory named "flask-app".
2. Inside "flask-app", create index.py containing this simple Flask application:

<code class="language-python"># index.py
from flask import Flask
app = Flask(__name__)
@app.route("/")
def hello():
    return "Hello World!"
if __name__ == "__main__":
    app.run(host="0.0.0.0", port=int("5000"), debug=True)</code>

3. Also in "flask-app", create a Dockerfile (no extension) with the following content:

<code class="language-dockerfile">FROM python:3.13.1-alpine3.21
WORKDIR /app
COPY . /app
RUN pip install -r requirements.txt
EXPOSE 5000
CMD ["python", "index.py"]</code>

4. Finally, create requirements.txt in the "flask-app" directory:

<code>Flask==2.3.2</code>

Your directory structure should now look like this:

<code>flask-app/
├── Dockerfile
├── index.py
└── requirements.txt</code>

Building and Running the Docker Image:

1. Navigate to the "flask-app" directory in your terminal.
2. Build the Docker image using this command:

<code class="language-bash">docker build -t flask-app .</code>

3. Verify the image was built successfully:

<code class="language-bash">docker images</code>

4. Run the Docker container, mapping port 5000 on your host machine to port 5000 in the container:

<code class="language-bash">docker run --name my-flask-app -d -p 5000:5000 flask-app</code>

5. Check the running container:

<code class="language-bash">docker ps -a</code>

6. Test the application by accessing http://127.0.0.1:5000 in your browser or using curl:

<code class="language-bash">curl http://127.0.0.1:5000</code>

7. To stop and remove the container:

<code class="language-bash">docker container rm -f my-flask-app</code>

8. To remove the image:

<code class="language-bash">docker image rm -f flask-app</code>

Pushing to Docker Hub:

Before pushing to Docker Hub, create an account if you don't have one already. Then:

1. Tag the image for Docker Hub (replace omerbsezer with your Docker Hub username):

<code class="language-bash">docker tag flask-app omerbsezer/dev-to-flask-app:latest</code>

2. Push the image:

<code class="language-bash">docker push omerbsezer/dev-to-flask-app:latest</code>

You can then see your image on Docker Hub. A screenshot would be placed here.

Conclusion:

This practical example demonstrates a complete workflow for containerizing a simple Python application with Docker. For more Docker tutorials, AWS, Kubernetes, Linux, DevOps, Ansible, Machine Learning, Generative AI, and SAAS content, follow these links:

• GitHub
• LinkedIn

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