DockerDockerizing Applications
Dockerizing A Basic Python Flask Application
Create a Docker image for a simple Flask application and run it with port mapping.
Python Flask applications are straightforward to dockerize.
The image needs Python, application files, dependencies from requirements.txt, and a command to start the Flask app.
Example project
flask-app/
app.py
requirements.txt
Dockerfilerequirements.txt:
flaskSimple app.py:
from flask import Flask
app = Flask(__name__)
@app.route("/")
def home():
return "Hello from Flask in Docker"
if __name__ == "__main__":
app.run(host="0.0.0.0", port=5000)The host must be 0.0.0.0 so the app can accept traffic from outside the container.
Dockerfile
FROM python:3.12-slim
WORKDIR /app
COPY requirements.txt .
RUN pip install --no-cache-dir -r requirements.txt
COPY . .
EXPOSE 5000
CMD ["python", "app.py"]Build and run
docker build -t flask-app:1.0 .
docker run -d -p 5000:5000 --name flask-web flask-app:1.0Open:
http://localhost:5000Common Flask mistake
If Flask runs only on 127.0.0.1, it listens inside the container only.
Use:
app.run(host="0.0.0.0", port=5000)This allows Docker port mapping to reach it.
For web apps inside containers, the app should listen on 0.0.0.0, and Docker should map the container port to a host port.
Written By: Shiva Srivastava
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