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I want to run a Docker container on my Raspberry PI 2 with a Python script that uses numpy. For this I have the following Dockerfile:

FROM python:3.7
COPY numpy_script.py /
RUN pip install numpy

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

But when I want to import numpy, I get the error message that libf77blas.so.3 was not found. I have also tried to install numpy with a wheel from www.piwheels.org, but the same error occurs.

The Google search revealed that I need to install the liblapack3. How do I need to modify my Dockerfile for this?

Inspired by the answer of om-ha, this worked for me:

FROM python:3.7
COPY numpy_script.py /
RUN apt-get update \
    && apt-get -y install libatlas-base-dev \
    && pip install numpy

CMD ["python", "numpy_script.py"]
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4
  • A. What's your host OS? B. From a host perspective, do you want this to be cross-platform (Windows/Linux)? Commented Apr 14, 2021 at 18:43
  • It's Raspberry Pi OS. Just want a lightweight docker container with a python script, not cross-platform Commented Apr 14, 2021 at 19:05
  • 1
    Done with my changes, check the answer if it works for you. Commented Apr 14, 2021 at 19:37
  • Thanks a lot, I am in bed now, but will give it a try as soon as I wake up Commented Apr 14, 2021 at 20:13

1 Answer 1

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2

Working Dockerfile

# Python image (debian-based)
FROM python:3.7

# Create working directory
WORKDIR /app

# Copy project files
COPY numpy_script.py numpy_script.py

# RUN command to update packages & install dependencies for the project
RUN apt-get update \
    && apt-get install -y \
    && pip install numpy

# Commands to run within the container
CMD ["python", "numpy_script.py"]

Explanation

  1. You have an extra trailing \ in your dockerfile, this is used for multi-line shell commands actually. You can see this used in-action here. I used this in my answer above. Beware the last shell command (in this case pip) does not need a trailing \, a mishap that was done in the code you showed.
  2. You should probably use a working directory via WORKDIR /app
  3. Run apt-get update just to be sure everything is up-to-date.
  4. It's recommended to group multiple shell commands within ONE RUN directive using &&. See best practices and this discussion.

Resources sorted by order of use in this dockerfile

  1. FROM
  2. WORKDIR
  3. COPY
  4. RUN
  5. CMD
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6 Comments

Hi, om-ha, thank you for given the working Dockerfile. I tried to build with above working Dockerfile in windows 10, which is working. However when I copied over image, and use docker to run the image on the Raspberry Pi 4, it says "The requested image's platform (linux/amd64) does not match the detected host platform (linux/arm/v7) and no specific platform was requested." I tried add build parameter --platform linux/armv7, which takes hour to build on windows 10. Is this behavior expected?
@WangYufan When building, specify the platform like this docker build --platform linux/arm/v7
Also refer to this issue for some inspiration.
You can specify the platform in the dockerfile, refer to [--platform=<platform>] in FROM documentation e.g. FROM --platform=linux/arm/v7 python:3.7
Finally, this could prove useful too: Multi-Platform Docker Builds.
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