Dockerfile to build a specific version of Python and set it as the default using Deadsnakes

Dockerfile.deadsnakes

# syntax=docker/dockerfile:1.7

FROM ubuntu:20.04

ARG PYTHON_VERSION="3.11"
ENV TZ=US/Chicago
ARG DEBIAN_FRONTEND=noninteractive

RUN <<EOF
#!/usr/bin/env bash
apt-get update -qq
apt-get install -qq --no-install-recommends -y \
    software-properties-common
add-apt-repository ppa:deadsnakes/ppa -y
apt-get update -qq
apt-get install -qq --no-install-recommends -y \
    python3-pip \
    python3.11 \
    python3.11-venv
apt-get clean
rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/*
EOF

RUN update-alternatives --install \
    /usr/bin/python3 python /usr/bin/python${PYTHON_VERSION} 1 \
    && update-alternatives --set python /usr/bin/python${PYTHON_VERSION} \
    && update-alternatives --set python /usr/bin/python${PYTHON_VERSION}