examples: add Devenv usage examples

examples/python-web-app/.dockerignore

@@ -0,0 +1,4 @@
+.geonix/*
+.result
+.venv/*
+src/python_app/__pycache__/*

examples/python-web-app/.gitignore

@@ -0,0 +1,13 @@
+# devenv
+.devenv*
+devenv.local.nix
+
+# direnv
+.direnv
+
+# pre-commit
+.pre-commit-config.yaml
+
+# python app
+src/python_app/__pycache__/*
+tests/__pycache__/

examples/python-web-app/Dockerfile

@@ -0,0 +1,25 @@
+# Get python-app-base image:
+#   nix build .#container
+#   docker load < ./result
+
+# Build image:
+#   docker build -t python-app:latest 
+
+FROM python-app-base
+
+RUN mkdir -p /opt/python-app
+WORKDIR /opt/python-app
+
+COPY src ./src
+COPY pyproject.toml poetry.* README.md ./
+
+RUN poetry install --without=dev
+
+RUN printf '#!/usr/bin/env bash \n\
+set -euo pipefail \n\
+source .venv/bin/activate \n\
+flask --app src/python_app run --host 0.0.0.0 --port 8000 \n\
+' > entrypoint.bash
+
+ENTRYPOINT [ "bash", "/opt/python-app/entrypoint.bash" ]
+EXPOSE 8000

examples/python-web-app/README.md

@@ -0,0 +1,146 @@
+# Example Python web application
+
+This is a example web application demonstrating development of Python
+application using dependencies provided by multiple sources.
+
+Application data can be generated by local Python server or by
+PostgreSQL/PostGIS database backend.
+
+Application is packaged in container image using traditional `Dockerfile`.
+
+## Dependencies
+
+### Provided by Geonix
+
+* shapely
+
+### Provided by Nixpkgs
+
+* matplotlib
+
+### Provided by Poetry
+
+* black
+* flask
+* isort
+* pytest
+
+
+## Template initialization
+
+```
+mkdir my-project
+cd my-project
+
+git init
+
+nix flake init --accept-flake-config --template github:imincik/geonix#python-web-app
+
+nix flake lock
+git add *
+```
+
+
+## Usage
+
+### Development (with local data backend)
+
+* Enter development shell
+
+```
+nix develop
+```
+
+* Install Python virtual environment using Poetry
+
+```
+poetry env use $(which python)
+poetry install
+```
+
+* Launch Python development server
+
+```
+poetry run flask --app src/python_app run --reload
+```
+
+* Exit development shell
+
+```
+exit
+```
+
+### Development (with database data backend)
+
+* Launch PostgreSQL database
+
+```
+nix develop .#postgresql
+```
+
+* Enter development shell (run in new terminal window)
+
+```
+nix develop
+```
+
+* Launch Python development server
+
+```
+BACKEND=db poetry run flask --app src/python_app run --reload
+```
+
+* Connect to PostgreSQL DB container (optional)
+
+```
+psql
+```
+
+* Exit development shell
+
+```
+exit
+```
+
+
+### Geonix CLI
+
+* Search for additional packages (run in development shell)
+
+```
+geonix search <PACKAGE>
+```
+
+
+## Deployment
+
+* Build and load base container image
+
+```
+nix build .#container
+docker load < ./result
+```
+
+* Build application container image
+
+```
+docker build -t python-app:latest .
+```
+
+* Run container
+
+```
+docker run --rm -p 8000:8000 python-app:latest
+```
+
+
+## Customized packages
+
+See
+[Customized packages](https://github.com/imincik/geonix/wiki/Customized-packages)
+for instructions how to customize packages.
+
+
+## More info
+
+* [Zero to Nix](https://zero-to-nix.com/)