The problem comes when you need things like ciso8601, or some libraries, requiring build process. Build tools are not "incorporated" into the both slim and alpine variants, for low-size footprint.

So to install deps, you'll have to:

• Install build tools
• Deploy dependencies from Pipfile.lock system-wide
• Uninstall build tools and clean caches

And do that 3 actions inside a single RUN layer, like following:

FROM python:3.7-slim

WORKDIR /app

# both files are explicitly required!
COPY Pipfile Pipfile.lock ./

RUN pip install pipenv && \
  apt-get update && \
  apt-get install -y --no-install-recommends gcc python3-dev libssl-dev && \
  pipenv install --deploy --system && \
  apt-get remove -y gcc python3-dev libssl-dev && \
  apt-get autoremove -y && \
  pip uninstall pipenv -y

COPY app ./

CMD ["python", "app.py"]

• Manipulating build system would cost you around 300MiB and some extra time
• Uninstalling pipenv would save you another 20MiB (which is 10% of resulting size).
• Separating RUN commands would not delete data from layers, and would result in ~500MiB image. That's docker specifics.

So that would result in perfectly working ~200MiB sized image, which is

• 5 times less than original python:3.7, (that is >1.0GiB)
• Has no alpine incompabilities (these are typically tied to glibc replacement)

At the time, we're fine with slim (debian buster) build variants, preferring slim over alpine (for most compatibility). If you're really up to further size optimization, I'd recommend you to take a look at some excellent builds of these guys:

• Alpine Python
• 12.7MiB MariaDB

If your environment is restricted enough that you can't use sudo to install packages, you won't be able to use Docker: if you can run any docker run command at all you can trivially get unrestricted root access on the host.

My python scripts needs a bit more modules which I can't install due to lack of sudo access & moreover, I dont want to screw up with the default Py which is needed for host to function.

That sounds like a perfect use for a virtual environment: it gives you an isolated local package tree that you can install into as an unprivileged user and doesn't interfere with the system Python. For Python 2 you need a separate tool for it, with a couple of steps to install:

export PYTHONUSERBASE=$HOME
pip install --user virtualenv
~/bin/virtualenv vpy
. vpy/bin/activate

pip install ... # installs into vpy/lib/python2.7/site-packages

RUN apt-get update

RUN apt-get install -y python3

As hinted by:

Acquire (13: Permission denied)

I believe this is due to your base image:

https://github.com/SeleniumHQ/docker-selenium/blob/master/NodeChrome/Dockerfile

As you can see it swaps from the default user context of 'root' to 'seluser'.

You can either:

1. wear this as a consequence of the base image (i.e. use sudo)
2. swap back: USER root
3. or consider creating your own docker image to avoid swapping in the first place

Using sudo is best avoided in Dockerfiles where possible, so it would be preferable to go with option #2 or #3, rather than #1.

Hope that helps mate.