Install Cython with python3 in Docker

Question

I'm using a Docker image from tensorflow with python3:

FROM tensorflow/tensorflow:latest-gpu-py3

I need Cython for a 3rd party library to be there, so I do

RUN curl -O https://bootstrap.pypa.io/get-pip.py && \
    python get-pip.py && \
    rm get-pip.py

RUN \ 
    pip install --no-cache-dir Cython

The problem is that after that I can see Cython from python, but not from python3:

root@fdb5bb783cf9:/darkflow# python3 -c "import Cython; print(Cython.__version__)"
Traceback (most recent call last):
  File "<string>", line 1, in <module>
ImportError: No module named 'Cython'
root@fdb5bb783cf9:/darkflow# python -c "import Cython; print(Cython.__version__)"
0.25.2

Solution

I have found that the solution was to use pip3 to run Cython install as well as python3 to run the setup.py of the library, so:

RUN apt-get update && apt-get install -y \
    python3-pip

and

RUN \ 
    pip3 install --no-cache-dir Cython

and the library layer

RUN \
    cd lib && \
    python3 setup.py

The last one could have been pip3 install . to install globally using pip3.

This time doing

RUN python3 -c "import Cython; print(Cython.__version__)"

I had Cython there: 0.25.2

Comments

[OscarAkaElvis]

Are you sure the image you are using has python3? is tagged as it is... but I repeat, are you sure?

[loretoparisi]

Thanks I have just realized I have missed something: apt-get install python3-pip, and pip3 install --no-cache-dir Cython, after that it worked!

[OscarAkaElvis]

Ok so put the answer yourself and mark it as resolved.