docker构建python3.7镜像：https://zhuanlan.zhihu.com/p/137288195

1. FROM：需要什么环境

   ENV：修改path，即增加/usr/local/bin这个环境变量

   ADD：将本地代码放到虚拟容器中，它有两个参数，第一个是 .
   ，代表本地当前路径；第二个参数是/code，代表虚拟容器中的路径，即将本地项目的所有内容放到虚拟容器的/code目录下，以便在虚拟容器中运行代码

   WORKDIR：指定工作目录，也就是刚才的/code，在虚拟容器中的目录

   RUN：执行某些环境准备工作，docker容器中只有python3环境，还需要python的库，这里安装那些库

   CMD：运行项目的命令行命令

打开python镜像地址
https://hub.docker.com/_/python

点击红色部分出现：

#
# NOTE: THIS DOCKERFILE IS GENERATED VIA "apply-templates.sh"
#
# PLEASE DO NOT EDIT IT DIRECTLY.
#

FROM buildpack-deps:bullseye

# 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

# runtime dependencies
RUN set -eux; \
	apt-get update; \
	apt-get install -y --no-install-recommends \
		libbluetooth-dev \
		tk-dev \
		uuid-dev \
	; \
	rm -rf /var/lib/apt/lists/*

ENV GPG_KEY 0D96DF4D4110E5C43FBFB17F2D347EA6AA65421D
ENV PYTHON_VERSION 3.7.13

RUN set -eux; \
	\
	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"; \
	GNUPGHOME="$(mktemp -d)"; export GNUPGHOME; \
	gpg --batch --keyserver hkps://keys.openpgp.org --recv-keys "$GPG_KEY"; \
	gpg --batch --verify python.tar.xz.asc python.tar.xz; \
	command -v gpgconf > /dev/null && gpgconf --kill all || :; \
	rm -rf "$GNUPGHOME" python.tar.xz.asc; \
	mkdir -p /usr/src/python; \
	tar --extract --directory /usr/src/python --strip-components=1 --file python.tar.xz; \
	rm python.tar.xz; \
	\
	cd /usr/src/python; \
	gnuArch="$(dpkg-architecture --query DEB_BUILD_GNU_TYPE)"; \
	./configure \
		--build="$gnuArch" \
		--enable-loadable-sqlite-extensions \
		--enable-optimizations \
		--enable-option-checking=fatal \
		--enable-shared \
		--with-system-expat \
		--with-system-ffi \
		--without-ensurepip \
	; \
	nproc="$(nproc)"; \
	make -j "$nproc" \
# setting PROFILE_TASK makes "--enable-optimizations" reasonable: https://bugs.python.org/issue36044 / https://github.com/docker-library/python/issues/160#issuecomment-509426916
		PROFILE_TASK='-m test.regrtest --pgo \
			test_array \
			test_base64 \
			test_binascii \
			test_binhex \
			test_binop \
			test_bytes \
			test_c_locale_coercion \
			test_class \
			test_cmath \
			test_codecs \
			test_compile \
			test_complex \
			test_csv \
			test_decimal \
			test_dict \
			test_float \
			test_fstring \
			test_hashlib \
			test_io \
			test_iter \
			test_json \
			test_long \
			test_math \
			test_memoryview \
			test_pickle \
			test_re \
			test_set \
			test_slice \
			test_struct \
			test_threading \
			test_time \
			test_traceback \
			test_unicode \
		' \
	; \
	make install; \
	\
# enable GDB to load debugging data: https://github.com/docker-library/python/pull/701
	bin="$(readlink -ve /usr/local/bin/python3)"; \
	dir="$(dirname "$bin")"; \
	mkdir -p "/usr/share/gdb/auto-load/$dir"; \
	cp -vL Tools/gdb/libpython.py "/usr/share/gdb/auto-load/$bin-gdb.py"; \
	\
	cd /; \
	rm -rf /usr/src/python; \
	\
	find /usr/local -depth \
		\( \
			\( -type d -a \( -name test -o -name tests -o -name idle_test \) \) \
			-o \( -type f -a \( -name '*.pyc' -o -name '*.pyo' -o -name '*.a' \) \) \
			-o \( -type f -a -name 'wininst-*.exe' \) \
		\) -exec rm -rf '{}' + \
	; \
	\
	ldconfig; \
	\
	python3 --version

# make some useful symlinks that are expected to exist ("/usr/local/bin/python" and friends)
RUN set -eux; \
	for src in idle3 pydoc3 python3 python3-config; do \
		dst="$(echo "$src" | tr -d 3)"; \
		[ -s "/usr/local/bin/$src" ]; \
		[ ! -e "/usr/local/bin/$dst" ]; \
		ln -svT "/usr/local/bin/$src" "/usr/local/bin/$dst"; \
	done

# if this is called "PIP_VERSION", pip explodes with "ValueError: invalid truth value '<VERSION>'"
ENV PYTHON_PIP_VERSION 22.0.4
# https://github.com/docker-library/python/issues/365
ENV PYTHON_SETUPTOOLS_VERSION 57.5.0
# https://github.com/pypa/get-pip
ENV PYTHON_GET_PIP_URL https://github.com/pypa/get-pip/raw/38e54e5de07c66e875c11a1ebbdb938854625dd8/public/get-pip.py
ENV PYTHON_GET_PIP_SHA256 e235c437e5c7d7524fbce3880ca39b917a73dc565e0c813465b7a7a329bb279a

RUN set -eux; \
	\
	wget -O get-pip.py "$PYTHON_GET_PIP_URL"; \
	echo "$PYTHON_GET_PIP_SHA256 *get-pip.py" | sha256sum -c -; \
	\
	export PYTHONDONTWRITEBYTECODE=1; \
	\
	python get-pip.py \
		--disable-pip-version-check \
		--no-cache-dir \
		--no-compile \
		"pip==$PYTHON_PIP_VERSION" \
		"setuptools==$PYTHON_SETUPTOOLS_VERSION" \
	; \
	rm -f get-pip.py; \
	\
	pip --version

CMD ["python3"]