如何从 python 中的 docker 访问环境变量？

Question

I have a Docker file which list environmental variable as follows:

ENV WORKGROUP "my-workgroup"

In python file I am accessing it as follows:

os.environ['WORKGROUP']

When I build the docker it fails with the following error:

KeyError: 'WORK_GROUP'

The reason is some environmental variables have some default values which I need to set in docker. I can override these inside docker run command when needed. Any idea how can I achieve such a scenario. Thanks.

Answer 1

I am usually doing like this in Dockerfile

ENV ENV_VAR=some_default_value

to start that kind of image and override env in image you can do this

docker run --env ENV_VAR=value_to_override

ENV_VAR will have some_default_value or value_to_override when image is started. (not during image build process). and os.environ['ENV_VAR'] sees that value just fine.

you may try docker build --no_cache so you are sure that image is rebuild completely.