Dockerfile for Python Application

What is Dockerfile

A Dockerfile is used to create a docker image. The Dockerfile contains all the commands that can be executed on command line to build an image. It's just a group of all commands that gets executed all together.

There are some common steps that are required to build an images for an application.

Point a base image

To build a Dockerfile for python application, a python base image should pointed. In the below example I have used python 3.9.7 image. There are different flavors of a python image like <code>python:<version></code>, <code>python:<version>-slim</code>, <code>python:<version>-alpine</code> and <code>python:<version>-windowsservercore</code>.

shell
1FROM python:3.9.7

Create application directory

The base image comes with some directories but always create your application directory. Create an application folder using below command.

shell
1RUN mkdir -p /home/app

Set root directory

Set the root directory where all the commands gets executed without telling the path. It should be absolute path.

shell
1WORKDIR /home/app

Copy source code

Now the source code from your local directory should be copied to the application directory created inside the Dockerfile.

shell
1COPY ./src/. /home/app/

Install dependencies

Install all python module dependencies. Python dependencies can be defined in requirements.txt file like package.json file. Use the below command to install all python dependencies.

shell
1RUN pip install --no-cache-dir -r requirements.txt

Command to init the application

A command the inits the application should be defined and that should run when the docker image runs. The <code>CMD</code> instruction is used to define such commands.

shell
1CMD [ "python", "index.py" ]

Complete Dockerfile

Here is the complete Dockerfile.

shell
1FROM python:3.9.7 LABEL maintainer="Onkar " RUN mkdir -p /home/app WORKDIR /home/app COPY ./src/. /home/app/ RUN pip install --no-cache-dir -r requirements.txt CMD [ "python", "index.py" ]

Once you create a Dockerfile, put that file in the root of your application.

Create Image

The <code>docker build</code> command is used to create a build. The below command will create a python application image (python_app_image) that your can run.

shell
1docker build -t python_app_image .

Run a Dockerfile

The <code>docker run</code> command is used to run a docker image. The below command will run the python image as container and the application will be accessible on 8000 port on localhost.

shell
1docker run -p 8000:8000 python_app