Dockerfile

FROM alpine:3.5

# ensure local python is preferred over distribution python
ENV PATH /usr/local/bin:$PATH

# http://bugs.python.org/issue19846
# > At the moment, setting "LANG=C" on a Linux system *fundamentally breaks Python 3*, and that's not OK.
ENV LANG C.UTF-8

# install ca-certificates so that HTTPS works consistently
# the other runtime dependencies for Python are installed later
RUN apk add --no-cache ca-certificates

ENV GPG_KEY 0D96DF4D4110E5C43FBFB17F2D347EA6AA65421D
ENV PYTHON_VERSION 3.6.1

# if this is called "PIP_VERSION", pip explodes with "ValueError: invalid truth value '<VERSION>'"
ENV PYTHON_PIP_VERSION 9.0.1
ENV PYTHON_SETUPTOOLS_VERSION 35.0.1
ENV PYTHON_WHEEL_VERSION 0.29.0

COPY musl-find_library.patch /

RUN set -ex \
	&& apk add --no-cache --virtual .fetch-deps \
		gnupg \
		libressl \
		tar \
		xz \
		patch \
	\
	&& wget -O python.tar.xz "https://www.python.org/ftp/python/${PYTHON_VERSION%%[a-z]*}/Python-$PYTHON_VERSION.tar.xz" \
	&& wget -O python.tar.xz.asc "https://www.python.org/ftp/python/${PYTHON_VERSION%%[a-z]*}/Python-$PYTHON_VERSION.tar.xz.asc" \
	&& export GNUPGHOME="$(mktemp -d)" \
	&& gpg --keyserver ha.pool.sks-keyservers.net --recv-keys "$GPG_KEY" \
	&& gpg --batch --verify python.tar.xz.asc python.tar.xz \
	&& rm -r "$GNUPGHOME" python.tar.xz.asc \
	&& mkdir -p /usr/src/python \
	&& tar -xJC /usr/src/python --strip-components=1 -f python.tar.xz \
	&& rm python.tar.xz \
	&& patch /usr/src/python/Lib/ctypes/util.py < musl-find_library.patch \
	&& rm musl-find_library.patch \
	\
	&& apk add --no-cache --virtual .build-deps  \
		bzip2-dev \
		gcc \
		gdbm-dev \
		musl-dev \
		linux-headers \
		make \
		ncurses-dev \
		libressl \
		libressl-dev \
		pax-utils \
		readline-dev \
		sqlite-dev \
		tcl-dev \
		tk \
		tk-dev \
		xz-dev \
		zlib-dev \
		libffi-dev \
		expat-dev \
# add build deps before removing fetch deps in case there's overlap
	&& apk del .fetch-deps \
	\
	&& cd /usr/src/python \
	&& rm -r Modules/expat \
		Modules/zlib \
		Modules/_ctypes/darwin* \
		Modules/_ctypes/libffi* \
	&& ./configure \
		--prefix=/usr \
		--enable-ipv6 \
		--enable-loadable-sqlite-extensions \
		--enable-shared \
		--enable-optimizations \
		--with-lto \
		--with-computed-gotos \
		--with-dbmliborder=gdbm:ndbm \
		--with-system-expat \
		--with-system-ffi \
		--with-threads \
	&& make -j$(getconf _NPROCESSORS_ONLN) \
	&& make install \
	\
# explicit path to "pip3" to ensure distribution-provided "pip3" cannot interfere
	&& if [ ! -e /usr/local/bin/pip3 ]; then : \
		&& wget -O /tmp/get-pip.py 'https://bootstrap.pypa.io/get-pip.py' \
		&& python3 /tmp/get-pip.py "pip==$PYTHON_PIP_VERSION" \
		&& rm /tmp/get-pip.py \
	; fi \
# we use "--force-reinstall" for the case where the version of pip we're trying to install is the same as the version bundled with Python
# ("Requirement already up-to-date: pip==8.1.2 in /usr/local/lib/python3.6/site-packages")
# https://github.com/docker-library/python/pull/143#issuecomment-241032683
	&& pip3 install --no-cache-dir --upgrade --force-reinstall \
		"pip==$PYTHON_PIP_VERSION" \
		"setuptools==$PYTHON_SETUPTOOLS_VERSION" \
		"wheel==$PYTHON_WHEEL_VERSION" \
	\
	&& find /usr/local -depth \
		\( \
			\( -type d -a -name test -o -name tests \) \
			-o \
			\( -type f -a -name '*.pyc' -o -name '*.pyo' \) \
		\) -exec rm -rf '{}' + \
	&& runDeps="$( \
		scanelf --needed --nobanner --recursive /usr/local \
			| awk '{ gsub(/,/, "\nso:", $2); print "so:" $2 }' \
			| sort -u \
			| xargs -r apk info --installed \
			| sort -u \
	)" \
	&& apk add --virtual .python-rundeps $runDeps \
	&& apk del .build-deps \
	&& rm -rf /usr/src/python ~/.cache

# make some useful symlinks that are expected to exist
RUN cd /usr/local/bin \
	&& { [ -e easy_install ] || ln -s easy_install-* easy_install; } \
	&& ln -s idle3 idle \
	&& ln -s pydoc3 pydoc \
	&& ln -s python3 python \
	&& ln -s python3-config python-config

CMD ["python3"]