Can I install python 3.7 in ubuntu 18.04 without having python 3.6 in the system?

Question

Please read the question carefully before closing as duplicate, I believe the use case to be unique.

I'm trying to create a docker image that only has python 3.7 installed, the problem is that if I try to install pip, the command also installs python 3.6 which I do not want.

The relevant part of the ideal docker file I'm tinkering is as follows

FROM ubuntu:18.04

# Upgrade installed packages
RUN apt-get update && apt-get upgrade -y && apt-get clean

# (...)

# Python package management and basic dependencies
RUN apt-get install -y python3.7 python3.7-dev python3.7-pip

# Register the version in alternatives
RUN update-alternatives --install /usr/bin/python python /usr/bin/python3.7 1

# Set python 3 as the default python
RUN update-alternatives --set python /usr/bin/python3.7

# Upgrade pip to latest version
RUN python -m ensurepip --upgrade

# (...)

This would fail as python3.7-pip doesn't seem to exist; only python3-pip does, which is what installs python 3.6 for some reason.

I tried not installing pip at all and doing it manually, like so

# (...)

RUN apt-get install -y python3.7 python3.7-dev

# (...)

RUN curl 'https://bootstrap.pypa.io/get-pip.py' > get-pip.py

RUN python get-pip.py pip --no-setuptools --no-wheel

Which fails with this error:

Traceback (most recent call last):
  File "get-pip.py", line 21492, in <module>
    main()
  File "get-pip.py", line 197, in main
    bootstrap(tmpdir=tmpdir)
  File "get-pip.py", line 82, in bootstrap
    import pip._internal
  File "/tmp/tmpbez2vju9/pip.zip/pip/_internal/__init__.py", line 40, in <module>
  File "/tmp/tmpbez2vju9/pip.zip/pip/_internal/cli/autocompletion.py", line 8, in <module>
  File "/tmp/tmpbez2vju9/pip.zip/pip/_internal/cli/main_parser.py", line 8, in <module>
  File "/tmp/tmpbez2vju9/pip.zip/pip/_internal/cli/cmdoptions.py", line 14, in <module>
ModuleNotFoundError: No module named 'distutils.util'

Again, installing python3-distutils results in python 3.6 appearing in the system

So, is there a way to install ONLY a fully functional python 3.7 in ubuntu 18.04, WITHOUT having to install python 3.6?

Answer 1

In case someone else is ok with getting Python3.6 installed as a side effect (python3.7-distutils introduces it as pointed out by OP). This will install Python3.7 making it default and have the latest available pip using your python3.7 installation

FROM ubuntu:18.04

# Upgrade installed packages
RUN apt-get update && apt-get upgrade -y && apt-get clean

# (...)

# Python package management and basic dependencies
RUN apt-get install -y curl python3.7 python3.7-dev python3.7-distutils

# Register the version in alternatives
RUN update-alternatives --install /usr/bin/python python /usr/bin/python3.7 1

# Set python 3 as the default python
RUN update-alternatives --set python /usr/bin/python3.7

# Upgrade pip to latest version
RUN curl -s https://bootstrap.pypa.io/get-pip.py -o get-pip.py && \
    python get-pip.py --force-reinstall && \
    rm get-pip.py


# (...)

Answer 2

I see two choices:

1. Using a Ubuntu image, leave the Python from system untouched. Install pyenv (https://github.com/pyenv/pyenv), then download a python 3.7 install, completely separated from system's Python.

or

2. Use the official Python image labeled 3.7.3-stretch or 3.7.3-slim-stretch (Debian)