Help with Dockerfile (Image for running Python file)

Dr. Will0hlep · July 15, 2025

So, I've wrote this dockerfile and it does the bare minimum. It allows a python coded discord bot to be run inside a docker container.

FROM python:3.10
ADD bot.py .
RUN pip install --upgrade pip
RUN pip install discord {other packages}
CMD [ "python", "./bot.py" ]

However, whenever I want to make changes to the code of the discord bot, I have to come back to this dockerfile and rebuild the image, then go into docker and build a new container from the newly rebuilt image. In an Ideal world, it would be great if all I had to do was replace the python file and, if needed, alter another file or an enviroment variable to add any new packages.

Problem is, I'm very new to this and I have very little idea how it would be done.

Anyone able to point me in the right direction?

AwesomeBFM · July 15, 2025

Docker Compose would be great for this
compose.yaml

services:
	bot:
    	build:
        	context: .
            dockerfile: Dockerfile

(indentation is wrong here, I can't get it quite right but just Google it)

This command builds and deploys the image & container

docker compose up --build

This command takes it down

docker compose down

igormp · July 15, 2025

1 hour ago, Dr. Will0hlep said:
So, I've wrote this dockerfile and it does the bare minimum. It allows a python coded discord bot to be run inside a docker container.
FROM python:3.10
ADD bot.py .
RUN pip install --upgrade pip
RUN pip install discord {other packages}
CMD [ "python", "./bot.py" ]
However, whenever I want to make changes to the code of the discord bot, I have to come back to this dockerfile and rebuild the image, then go into docker and build a new container from the newly rebuilt image. In an Ideal world, it would be great if all I had to do was replace the python file and, if needed, alter another file or an enviroment variable to add any new packages.

Problem is, I'm very new to this and I have very little idea how it would be done.

Anyone able to point me in the right direction?

First, it'd be nice if you gave a read at how a dockerfile works, specially when it comes to layers and caching. This is a great resource with an overview:

https://docs.docker.com/build/cache/

A container is immutable, so once it's built, you should not edit it. With that said, what's taking place is that, given how your "bot.py" file is on the first line, it will throw away most of the cache and rebuild everything from that point onwards.

First of all, it'd be nice for you to have at least a "requirements.txt" file, with your dependencies and their versions stored in there. This way you could first copy this, and then install the required dependencies.

Let's say you now have such file, with the following contents:

discord.py==2.5.2
requests==2.32.4

You could have your Dockerfile looking like so:

FROM python:3.10
RUN pip install --upgrade pip

# The below will only copy and install your dependencies
COPY requirements.txt ./requirements.txt
# Will create a cached layer with your installed dependencies. If no changes happen to the requirements.txt file, this will just be reused in other build calls
RUN pip install -r requirements.txt

# Copy only your actual code. Any changes that you do to this file will only update this layer, while re-using the above ones that already exist
COPY bot.py ./bot.py

CMD [ "python", "./bot.py" ]

It will still require you to rebuild the image and re-deploy it, but that's exactly how it's meant to be done.

You could either automate this process with some sort of CI/CD pipeline, or you could just not use Docker and use something else instead, like a VM or just running your code straight out of a venv.

1 hour ago, AwesomeBFM said:

Docker Compose would be great for this

I don't think compose is a good suggestion, specially when we're talking about a single container.

Kilrah · July 15, 2025

Mount an external folder (or single file) to the container.

e.g. don't do "ADD bot.py ." in the Dockerfile, but when you run the container add a

-v /hostpath/to/bot.py:/innerpath/bot.py

with

CMD [ "python", "/innerpath/bot.py" ]

Dr. Will0hlep · July 18, 2025

On 7/15/2025 at 9:25 PM, Kilrah said:

Mount an external folder (or single file) to the container.

e.g. don't do "ADD bot.py ." in the Dockerfile, but when you run the container add a

-v /hostpath/to/bot.py:/innerpath/bot.py

with

CMD [ "python", "/innerpath/bot.py" ]

After a bit of fiddeling, practice, and trial and error, I've ended up with this yaml script:

services:
  inglewood:
    build:
      context: /mnt/Pool/Storage/Inglewood/
      dockerfile: Dockerfile
    container_name: inglewood
    environment:
      - PYTHONUNBUFFERED=1
    restart: unless-stopped
    volumes:
      - /mnt/Pool/Storage/Inglewood:/app

which I can use to create a custom app on TrueNAS Scale. It uses this dockerfile:

FROM python:3.10
RUN pip install --upgrade pip
RUN pip install discord mcstatus pytz
CMD [ "python3", "/app/inglewood.py" ]

,which is saved at "/mnt/Pool/Storage/Inglewood/Dockerfile", to create a container that runs my discord bot, or any python script saved at "/mnt/Pool/Storage/Inglewood/inglewood.py".

This achieves exactly what I wanted. In order to alter the behaviour of my discord bot, I now only need to change the python script (and maybe the dockerfile if I need to add new packages) and then restart the app in the TrueNAS Scale web UI. Perfect.