Install python in docker

Dockerfile

FROM ubuntu:focal

RUN : \
    && apt-get update \
    && DEBIAN_FRONTEND=noninteractive apt-get install -y --no-install-recommends \
        gnupg2 \
        python3-pip \
        software-properties-common \
    && add-apt-repository ppa:deadsnakes \
    && DEBIAN_FRONTEND=noninteractive apt-get install -y --no-install-recommends \
        python3.9-dev \
        python3.9-distutils \
    && apt-get clean \
    && rm -rf /var/lib/apt/lists/*

CMD ["python3.9", "-m", "pip", "--help"]