Python + Poetry + Docker Example

app.py

from flask import Flask
app = Flask(__name__)

@app.route('/')
def hello_world():
    return 'Hello, Docker!'

Dockerfile

FROM python:3.10 as python-base

# https://python-poetry.org/docs#ci-recommendations
ENV POETRY_VERSION=1.2.0
ENV POETRY_HOME=/opt/poetry
ENV POETRY_VENV=/opt/poetry-venv

# Tell Poetry where to place its cache and virtual environment
ENV POETRY_CACHE_DIR=/opt/.cache

# Create stage for Poetry installation
FROM python-base as poetry-base

# Creating a virtual environment just for poetry and install it with pip
RUN python3 -m venv $POETRY_VENV \
	&& $POETRY_VENV/bin/pip install -U pip setuptools \
	&& $POETRY_VENV/bin/pip install poetry==${POETRY_VERSION}

# Create a new stage from the base python image
FROM python-base as example-app

# Copy Poetry to app image
COPY --from=poetry-base ${POETRY_VENV} ${POETRY_VENV}

# Add Poetry to PATH
ENV PATH="${PATH}:${POETRY_VENV}/bin"

WORKDIR /app

# Copy Dependencies
COPY poetry.lock pyproject.toml ./

# [OPTIONAL] Validate the project is properly configured
RUN poetry check

# Install Dependencies
RUN poetry install --no-interaction --no-cache --without dev

# Copy Application
COPY . /app

# Run Application
EXPOSE 5000
CMD [ "poetry", "run", "python", "-m", "flask", "run", "--host=0.0.0.0" ]

minimal.Dockerfile

FROM python:3.10

# Configure Poetry
ENV POETRY_VERSION=1.2.0
ENV POETRY_HOME=/opt/poetry
ENV POETRY_VENV=/opt/poetry-venv
ENV POETRY_CACHE_DIR=/opt/.cache

# Install poetry separated from system interpreter
RUN python3 -m venv $POETRY_VENV \
	&& $POETRY_VENV/bin/pip install -U pip setuptools \
	&& $POETRY_VENV/bin/pip install poetry==${POETRY_VERSION}

# Add `poetry` to PATH
ENV PATH="${PATH}:${POETRY_VENV}/bin"

WORKDIR /app

# Install dependencies
COPY poetry.lock pyproject.toml ./
RUN poetry install

# Run your app
COPY . /app
CMD [ "poetry", "run", "python", "-c", "print('Hello, World!')" ]

poetry.lock

[[package]]
name = "click"
version = "8.1.3"
description = "Composable command line interface toolkit"
category = "main"
optional = false
python-versions = ">=3.7"

[package.dependencies]
colorama = {version = "*", markers = "platform_system == \"Windows\""}

[[package]]
name = "colorama"
version = "0.4.5"
description = "Cross-platform colored terminal text."
category = "main"
optional = false
python-versions = ">=2.7, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*, !=3.4.*"

[[package]]
name = "flask"
version = "2.2.2"
description = "A simple framework for building complex web applications."
category = "main"
optional = false
python-versions = ">=3.7"

[package.dependencies]
click = ">=8.0"
itsdangerous = ">=2.0"
Jinja2 = ">=3.0"
Werkzeug = ">=2.2.2"

[package.extras]
async = ["asgiref (>=3.2)"]
dotenv = ["python-dotenv"]

[[package]]
name = "itsdangerous"
version = "2.1.2"
description = "Safely pass data to untrusted environments and back."
category = "main"
optional = false
python-versions = ">=3.7"

[[package]]
name = "jinja2"
version = "3.1.2"
description = "A very fast and expressive template engine."
category = "main"
optional = false
python-versions = ">=3.7"

[package.dependencies]
MarkupSafe = ">=2.0"

[package.extras]
i18n = ["Babel (>=2.7)"]

[[package]]
name = "markupsafe"
version = "2.1.1"
description = "Safely add untrusted strings to HTML/XML markup."
category = "main"
optional = false
python-versions = ">=3.7"

[[package]]
name = "werkzeug"
version = "2.2.2"
description = "The comprehensive WSGI web application library."
category = "main"
optional = false
python-versions = ">=3.7"

[package.dependencies]
MarkupSafe = ">=2.1.1"

[package.extras]
watchdog = ["watchdog"]

[metadata]
lock-version = "1.1"
python-versions = "^3.10"
content-hash = "181ecf21593eeadd78073fcdba99b6207d2101817871cd0a31056b4301628404"

[metadata.files]
click = [
    {file = "click-8.1.3-py3-none-any.whl", hash = "sha256:bb4d8133cb15a609f44e8213d9b391b0809795062913b383c62be0ee95b1db48"},
    {file = "click-8.1.3.tar.gz", hash = "sha256:7682dc8afb30297001674575ea00d1814d808d6a36af415a82bd481d37ba7b8e"},
]
colorama = [
    {file = "colorama-0.4.5-py2.py3-none-any.whl", hash = "sha256:854bf444933e37f5824ae7bfc1e98d5bce2ebe4160d46b5edf346a89358e99da"},
    {file = "colorama-0.4.5.tar.gz", hash = "sha256:e6c6b4334fc50988a639d9b98aa429a0b57da6e17b9a44f0451f930b6967b7a4"},
]
flask = [
    {file = "Flask-2.2.2-py3-none-any.whl", hash = "sha256:b9c46cc36662a7949f34b52d8ec7bb59c0d74ba08ba6cb9ce9adc1d8676d9526"},
    {file = "Flask-2.2.2.tar.gz", hash = "sha256:642c450d19c4ad482f96729bd2a8f6d32554aa1e231f4f6b4e7e5264b16cca2b"},
]
itsdangerous = [
    {file = "itsdangerous-2.1.2-py3-none-any.whl", hash = "sha256:2c2349112351b88699d8d4b6b075022c0808887cb7ad10069318a8b0bc88db44"},
    {file = "itsdangerous-2.1.2.tar.gz", hash = "sha256:5dbbc68b317e5e42f327f9021763545dc3fc3bfe22e6deb96aaf1fc38874156a"},
]
jinja2 = [
    {file = "Jinja2-3.1.2-py3-none-any.whl", hash = "sha256:6088930bfe239f0e6710546ab9c19c9ef35e29792895fed6e6e31a023a182a61"},
    {file = "Jinja2-3.1.2.tar.gz", hash = "sha256:31351a702a408a9e7595a8fc6150fc3f43bb6bf7e319770cbc0db9df9437e852"},
]
markupsafe = [
    {file = "MarkupSafe-2.1.1-cp310-cp310-macosx_10_9_universal2.whl", hash = "sha256:86b1f75c4e7c2ac2ccdaec2b9022845dbb81880ca318bb7a0a01fbf7813e3812"},
    {file = "MarkupSafe-2.1.1-cp310-cp310-macosx_10_9_x86_64.whl", hash = "sha256:f121a1420d4e173a5d96e47e9a0c0dcff965afdf1626d28de1460815f7c4ee7a"},
    {file = "MarkupSafe-2.1.1-cp310-cp310-manylinux_2_17_aarch64.manylinux2014_aarch64.whl", hash = "sha256:a49907dd8420c5685cfa064a1335b6754b74541bbb3706c259c02ed65b644b3e"},
    {file = "MarkupSafe-2.1.1-cp310-cp310-manylinux_2_17_x86_64.manylinux2014_x86_64.whl", hash = "sha256:10c1bfff05d95783da83491be968e8fe789263689c02724e0c691933c52994f5"},
    {file = "MarkupSafe-2.1.1-cp310-cp310-manylinux_2_5_i686.manylinux1_i686.manylinux_2_17_i686.manylinux2014_i686.whl", hash = "sha256:b7bd98b796e2b6553da7225aeb61f447f80a1ca64f41d83612e6139ca5213aa4"},
    {file = "MarkupSafe-2.1.1-cp310-cp310-musllinux_1_1_aarch64.whl", hash = "sha256:b09bf97215625a311f669476f44b8b318b075847b49316d3e28c08e41a7a573f"},
    {file = "MarkupSafe-2.1.1-cp310-cp310-musllinux_1_1_i686.whl", hash = "sha256:694deca8d702d5db21ec83983ce0bb4b26a578e71fbdbd4fdcd387daa90e4d5e"},
    {file = "MarkupSafe-2.1.1-cp310-cp310-musllinux_1_1_x86_64.whl", hash = "sha256:efc1913fd2ca4f334418481c7e595c00aad186563bbc1ec76067848c7ca0a933"},
    {file = "MarkupSafe-2.1.1-cp310-cp310-win32.whl", hash = "sha256:4a33dea2b688b3190ee12bd7cfa29d39c9ed176bda40bfa11099a3ce5d3a7ac6"},
    {file = "MarkupSafe-2.1.1-cp310-cp310-win_amd64.whl", hash = "sha256:dda30ba7e87fbbb7eab1ec9f58678558fd9a6b8b853530e176eabd064da81417"},
    {file = "MarkupSafe-2.1.1-cp37-cp37m-macosx_10_9_x86_64.whl", hash = "sha256:671cd1187ed5e62818414afe79ed29da836dde67166a9fac6d435873c44fdd02"},
    {file = "MarkupSafe-2.1.1-cp37-cp37m-manylinux_2_17_aarch64.manylinux2014_aarch64.whl", hash = "sha256:3799351e2336dc91ea70b034983ee71cf2f9533cdff7c14c90ea126bfd95d65a"},
    {file = "MarkupSafe-2.1.1-cp37-cp37m-manylinux_2_17_x86_64.manylinux2014_x86_64.whl", hash = "sha256:e72591e9ecd94d7feb70c1cbd7be7b3ebea3f548870aa91e2732960fa4d57a37"},
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    {file = "MarkupSafe-2.1.1-cp37-cp37m-musllinux_1_1_x86_64.whl", hash = "sha256:e1c0b87e09fa55a220f058d1d49d3fb8df88fbfab58558f1198e08c1e1de842a"},
    {file = "MarkupSafe-2.1.1-cp37-cp37m-win32.whl", hash = "sha256:8dc1c72a69aa7e082593c4a203dcf94ddb74bb5c8a731e4e1eb68d031e8498ff"},
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    {file = "MarkupSafe-2.1.1-cp38-cp38-manylinux_2_17_x86_64.manylinux2014_x86_64.whl", hash = "sha256:4b9fe39a2ccc108a4accc2676e77da025ce383c108593d65cc909add5c3bd601"},
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    {file = "MarkupSafe-2.1.1-cp39-cp39-musllinux_1_1_i686.whl", hash = "sha256:43093fb83d8343aac0b1baa75516da6092f58f41200907ef92448ecab8825135"},
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    {file = "MarkupSafe-2.1.1.tar.gz", hash = "sha256:7f91197cc9e48f989d12e4e6fbc46495c446636dfc81b9ccf50bb0ec74b91d4b"},
]
werkzeug = [
    {file = "Werkzeug-2.2.2-py3-none-any.whl", hash = "sha256:f979ab81f58d7318e064e99c4506445d60135ac5cd2e177a2de0089bfd4c9bd5"},
    {file = "Werkzeug-2.2.2.tar.gz", hash = "sha256:7ea2d48322cc7c0f8b3a215ed73eabd7b5d75d0b50e31ab006286ccff9e00b8f"},
]

pyproject.toml

[tool.poetry]
name = "python-poetry-docker-example"
version = "0.1.0"
description = ""
authors = ["Someone <[email protected]>"]

[tool.poetry.dependencies]
python = "^3.10"
Flask = "^2.1.2"

[tool.poetry.dev-dependencies]

[build-system]
requires = ["poetry-core>=1.0.0"]
build-backend = "poetry.core.masonry.api"

Is .lock necessary if anyway you use poetry install to generate it?

poetry install does not generate the lock file, it uses it to "know" which packages to install.
Using the poetry.lock file ensures that every time you run poetry install you will get the same set of packages* into your {,virtual} Python environment.
@Simon-The-Human, you can read all about it in the poetry docs.

Self Nit

The lockfile contains multiple soltions to your dependency tree, each solution targeting a different os, cpu arch, python version that you are using.