TL;DR Docker is a great tool for managing software environments, but we found that it’s just too slow, especially for… More on reddit.com

If you're using pycharm or vsc or similar you might need to set the python version to use in the settings. More on reddit.com

One thing about pip is it lets you easily choose which version of a module you want, so it helps you in a scenario where you want to easily upgrade ("pip --upgrade mymodule"), or choose a specific version ("pip install mymodule==2.3" ). More on reddit.com

How do I know which python is being used when I call this command That would depend on a few things: The shebang (the first line in the file normally) The PATH variable in the env of the running command What is installed on that container In this case, the ENTRYPOINT as that is non-default Normally I would suggest running something like: docker run -it cytopia/mypy sh However, I tried it and it didn't work for me, because they have configured a custom ENTRYPOINT, instead you can do this: docker run -it --entrypoint '/bin/sh' cytopia/mypy This gives me a shell that I can use to check out the env: /data # echo $PATH /usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin /data # which python /usr/bin/python /data # python Python 3.10.9 (main, Dec 10 2022, 13:54:12) [GCC 11.2.1 20220219] on linux Anyway, the files they use to create the image can be found here I think (this one is for 3.10): https://github.com/cytopia/docker-mypy/blob/master/Dockerfiles/Dockerfile.python3.10 and how can I install the required dependencies to this particular python installation so mypy can run properly The normal way to do this would be to create a new DockerFile, which uses the image you want as the FROM and then adds dependencies. The image itself is based on alpine linux (a secure and lightweight focused linux often used for building small images) and so you would want to install stuff using apk I believe: FROM cytopia/mypy RUN apk add py3-pip && pip install numpy For example will create a new image with numpy installed for you I am not sure why I had to install pip... I can see it gets installed in the DockerFile and when I tried to use pip in my container, I got an error that it couldn't be found... Beware, that each time you use RUN, it creates a new layer. If you create a new layer and create a load of cache files on that layer they will make your image very big, you will want to tidy up each layer as you go (but I guess that's something you will learn as you go) You would then be able to run your previous docker run with the new image you have built with the dependencies installed More on reddit.com