Changing the version of Python in Dockerfile

General
1

Hi all

I am using Ubuntu 16.04; I am trying to run a nodejs program from docker. Within this program I need to be able to spawn a python script (which is only compatible with python 3.6 and above).

In order to test that the correct version of python is being used from within the node program I have a very simple piece of code

 const { spawn } = require('child_process');
 var proc = spawn('python3', ['--version']);

 proc.stdout.on('data', (data) => {
        console.log(`stdout: ${data}`);
 });

However, try as I might, this program always produces the output:

stdout: Python 3.5.3

I have been unable to find a way to get the version of python up to 3.6

My Dockerfile:

FROM ubuntu:16.04
RUN apt-get update && apt-get install -y software-properties-common && add-apt-repository ppa:deadsnakes/ppa && apt-get update && apt-get install -y python3.7 python3.7-dev python3-pip

RUN ln -sfn /usr/bin/python3.7 /usr/bin/python3 && ln -sfn /usr/bin/python3 /usr/bin/python && ln -sfn /usr/bin/pip3 /usr/bin/pip

FROM node:12
ADD demo ./demo
ADD aries_cloudagent ./aries_cloudagent
ADD ./demo/runners/nodejs/ ./nodejs
ADD bin ./bin

RUN npm install --prefix ./nodejs

CMD node ./nodejs/alice.js

`
I get the same result regardless of whether the first two RUN lines are there: they seem to have no effect.

I am at a loss to know how to fix this. Any ideas?

2

Hi

The reason for this is that you use multistage builds
And you dont actually benefit from it, these kind of builds is good if you compile/build something in the first stage, and then copy that to the last stage, that way you remove a bit of program/files used for the building part.

So, this wont work (imo) for you.

What i would do, is to take the node 12 image, that uses debian. fx: node:12-buster, and only that, and install python whinin the node image, if i remember correctly, the default python version in buster is 3.7

Hope it makes sense :slight_smile:

3

Thank you Martin, I tried the same Dockerfile with node:13.12.0-buster and it now uses python 3.7.3 correctly.

You’re right about the multistage build, I think that was just something I put in as one of those “try it and see” moments.

Much appreciated
Mike

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