An example Dockerfile which spits out an RPM package on build.

FPM Dockerfile example

FROM centos:centos7

# Yum packages to install.
ENV YUM_PACKAGES \
    which \
    gcc \
    libffi-devel \
    openssl-devel \
    git \
    ruby-devel \
    python-devel \
    rubygems \
    rpm-build \
    make \
    curl \
    python-setuptools \
    python-setuptools-devel

# Gems to install.
ENV GEM_PACKAGES \
    fpm

# fpm argument vars.
ENV PACKAGE_NAME         "MyPackage"
ENV PACKAGE_VERSION      "1.0.0-0"
ENV PACKAGE_ARCH         "noarch"
ENV WORKSPACE_PATH       "/tmp"
ENV PACKAGE_INSTALL_PATH "/opt"

# Install YUM packages.
RUN yum makecache && \
    yum install -y $YUM_PACKAGES

# Install Gems.
RUN gem install $GEM_PACKAGES

# Install pip.
RUN curl "https://bootstrap.pypa.io/get-pip.py" -o "get-pip.py" && \
    python get-pip.py

# Create the workspace and output directories.
RUN mkdir -p "${WORKSPACE_PATH}${PACKAGE_INSTALL_PATH}" && \
    mkdir /output

WORKDIR "${WORKSPACE_PATH}"

ADD $PACKAGE_NAME "${PACKAGE_INSTALL_PATH#/}/${PACKAGE_NAME}" && \
    fpm -f \
        --verbose \
        -t rpm \
        -s python \
        --provides $PACKAGE_NAME \
        -n $PACKAGE_NAME \
        -v $PACKAGE_VERSION \
        -a all \
        -p "/output/${PACKAGE_NAME}-${PACKAGE_VERSION}.${PACKAGE_ARCH}.rpm" \
        --before-install "${PACKAGE_INSTALL_PATH#/}/${PACKAGE_NAME}/before-install.sh" \
        --after-install "${PACKAGE_INSTALL_PATH#/}/${PACKAGE_NAME}/after-install.sh" \
        -d 'gcc' \
        -d 'libffi-devel' \
        -d 'openssl-devel' \
        -d 'python-setuptools' \
        -d 'python-devel' \
        -d 'python-urllib3' \
        "${PACKAGE_INSTALL_PATH#/}/${PACKAGE_NAME}/setup.py"

# The RPM should extract our Python somewhere like:
# /usr/lib/python2.7/site-packages/${PACKAGE_NAME}/