Save docker output file in workdir

Question

I am a newby in docker My Dockerfile

FROM python:3
WORKDIR /app
COPY . /app
RUN pip install numpy
RUN pip install pandas
CMD ["python", "app.py"]

And in app.py I have a line

pd.DataFrame(predictions, columns=['predictions']).to_csv('output.csv')

I build and run the image, that's ok but I can not to save this dataframe in my work directory. How to change Dockerfile so that I can do it?

What do you want to achieve exactly? Do you need the output on your host machine? Or is output.csv not being created in /app at all? — bellackn
– bellackn, Commented May 1, 2019 at 15:46

bellackn · Accepted Answer · 2019-05-01 16:05:14Z

2

Probably the best way to get output.csv out of the container onto your host machine is using a volume. Volumes are storage paths that can be shared between host and container, much like shared folders for VMs.

In your case:

docker run --rm -v $(pwd)/volume:/app your_image

You should then find everything from the container's /app path in your working directory under ./volume.

answered May 1, 2019 at 16:05

bellackn

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7 Comments

Proyag Over a year ago

It looks like /app is not empty, from to the COPY instruction in the Dockerfile. The original contents of /app would get hidden when the volume is mounted this way. Using any other path to mount the volume instead of /app should be fine in this case.

Edward Over a year ago

@Proyag can I delete COPY or change WORKDIR in Dockerfile?

bellackn Over a year ago

I agree, @Proyag. @Edward, you could change your Python code to save your CSV somewhere else, e.g. /home/your_user/output.csv. Then you would change the volume definition to -v $(pwd)/volume:/home/your_user.

Edward Over a year ago

I use docker run --rm -v $(pwd)/volume:/e/test my_image It works but the output is not saved. If I channge in app.py `to_csv('/e/test/output.csv') I get error

Edward Over a year ago

No such file or directory

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