Support Python packaging

.github/workflows/python-package-tests.yml

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+name: Python Package Tests
+
+on:
+  push:
+    branches: [ master ]
+  pull_request:
+    branches: [ master ]
+
+jobs:
+  build-wheel:
+    runs-on: ubuntu-latest
+    container: ghcr.io/gridtools/gridtools-base:${{ matrix.compiler }}
+    strategy:
+        matrix:
+            python-version: ["3.10"]
+            compiler: [gcc-10]
+            build_type: [release]
+    steps:
+    - uses: actions/checkout@v2
+    - name: Set up Python ${{ matrix.python-version }}
+      uses: actions/setup-python@v2
+      with:
+        python-version: ${{ matrix.python-version }}
+    - name: install nox
+      run: |
+        python -m pip install --upgrade pip setuptools
+        python -m pip install nox
+    - name: run tests
+      working-directory: ./.python_package
+      run: nox -s test_src
+    - name: build and test wheel
+      working-directory: ./.python_package
+      run: nox -s build_wheel test_wheel_with_python-${{ matrix.python-version }}
+    - name: archive wheel
+      uses: actions/upload-artifact@v3
+      with:
+        name: gridtools-cpp-wheel
+        path: .python_package/.nox/.cache/dist/gridtools_cpp-*.whl
+
+  test-wheel:
+    needs: build-wheel
+    runs-on: ubuntu-latest
+    container: ghcr.io/gridtools/gridtools-base:${{ matrix.compiler }}
+    strategy:
+      matrix:
+        python-version: ["3.8", "3.9", "3.11"]
+        compiler: [gcc-10]
+    steps:
+    - uses: actions/checkout@v2
+    - name: Set up Python ${{ matrix.python-version }}
+      uses: actions/setup-python@v2
+      with:
+        python-version: ${{ matrix.python-version }}
+    - name: install nox
+      run: |
+        python -m pip install --upgrade pip setuptools
+        python -m pip install nox
+    - name: download wheel
+      uses: actions/download-artifact@v3
+      with:
+        name: gridtools-cpp-wheel
+        path: .python_package/.nox/.cache/dist
+    - name: test wheel
+      working-directory: ./.python_package
+      run: nox -s test_wheel_with_python-${{ matrix.python-version }}

.python_package/README.md

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+# Python package for GridTools headers and CMake files
+
+## Usage
+
+Use the following when compiling C++ code with GridTools programmatically from Python.
+Either by calling a compiler directly or by generating a CMake project and calling CMake on it.
+
+```python
+import gridtools_cpp
+include_dir = gridtools_cpp.get_include_dir()   # header files can be found here
+cmake_dir = gridtools_cpp.get_cmake_dir()       # cmake files can be found here
+```
+
+## Development
+
+In order to be able to work on this package, it is necessary to run a preparation step.
+This will generate the `setup.cfg` file from `setup.cfg.in` and install the gridtools header distribution into the package data.
+It will read the version number from the top-level `version.txt` and copy the `LICENSE` file to where packaging tools can find it.
+
+All of this requires `nox`, the preparation step runs in an isolated environment and installs additional requirements `cmake` and `ninja` at runtime.
+
+```bash
+pip install nox
+nox -s prepare
+```
+
+To delete all generated files run
+
+```bash
+nox -s clean clean_cache
+```
+
+where `clean_cache` deletes chached files from Nox sessions like CMake builds and testing wheels (found in `.nox/.cache`), and `clean` deletes visible artifacts like `dist/`, `build/`, `.egg-info/`.
+`setup.cfg` will not be deleted for convenience, to make sure tools keep functioning as expected.
+
+### Installing
+
+As always it is recommended to carry out the following steps in a virtual environment:
+
+```bash
+nox -s build -- --wheel .
+pip install dist/gridtools_cpp-2.2.0-py3-none-any.whl
+```
+
+### Testing
+
+Using nox, the tests will be carried out in isolated python environments for you:
+
+```bash
+nox -s test_src
+```
+
+To test the wheel distribution specifically:
+
+```bash
+nox -s build_wheel test_wheel_with_python-3.10  # replace 3.10 with the Python version you are running
+```
+
+### Advanced testing (all supported versions)
+
+The following requires you to have Python interpreters for Python 3.8, 3.9, 3.10 and 3.11 in your system path.
+
+```bash
+nox
+```
+
+### Building for distribution
+
+Uses (`build`)[https://pypa-build.readthedocs.io/en/latest/], follow the link for available options.
+
+```bash
+nox -s build -- <build options>
+```

.python_package/noxfile.py

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+# GridTools
+#
+# Copyright (c) 2014-2021, ETH Zurich
+# All rights reserved.
+#
+# Please, refer to the LICENSE file in the root directory.
+# SPDX-License-Identifier: BSD-3-Clause
+
+import configparser
+import pathlib
+import shutil
+
+import nox
+
+
+_RELATIVE_DATA_DIR = pathlib.Path("src/gridtools_cpp/data")
+
+
+nox.options.sessions = ["test_src", "test_wheel"]
+
+
+@nox.session
+def prepare(session: nox.Session):
+    session.install("cmake>=3.18.1")
+    session.install("ninja")
+    build_path = session.cache_dir.joinpath("build").absolute()
+    build_path.mkdir(exist_ok=True)
+    install_path = pathlib.Path(".").absolute() / _RELATIVE_DATA_DIR
+    source_path = pathlib.Path("..").absolute()
+    with session.chdir(build_path):
+        session.run(
+            "cmake",
+            "-DBUILD_TESTING=OFF",
+            "-DGT_INSTALL_EXAMPLES:BOOL=OFF",
+            f"-DCMAKE_INSTALL_PREFIX={install_path}",
+            "-GNinja",
+            str(source_path),
+        )
+        session.run("cmake", "--install", ".")
+        session.log("installed gridttols sources")
+    version_path = source_path / "version.txt"
+    config = configparser.ConfigParser()
+    config.read("setup.cfg.in")
+    config["metadata"]["version"] = version_path.read_text().strip()
+    with open("setup.cfg", mode="w") as setup_fp:
+        config.write(setup_fp)
+    session.log("updated version metadata")
+    shutil.copy(source_path / "LICENSE", ".")
+    session.log("copied license file")
+
+
+def get_wheel(session: nox.Session) -> pathlib.Path:
+    return list(session.cache_dir.joinpath("dist").glob("gridtools_cpp-*.whl"))[0]
+
+
+@nox.session
+def build_wheel(session: nox.Session):
+    prepare(session)
+    dist_path = session.cache_dir.joinpath("dist").absolute()
+    nox_workdir = pathlib.Path(".").absolute()
+    session.install("build[virtualenv]")
+    with session.chdir(session.cache_dir):
+        session.run(
+            "python",
+            "-m",
+            "build",
+            "--no-isolation",
+            "--wheel",
+            "-o",
+            str(dist_path),
+            str(nox_workdir),
+        )
+    session.log(f"built wheel in {dist_path}")
+    session.log("\n".join(str(path) for path in dist_path.iterdir()))
+
+
+@nox.session
+def test_src(session: nox.Session):
+    prepare(session)
+    session.install(".")
+    session.install("pytest")
+    session.run("pytest", "tests", *session.posargs)
+
+
+@nox.session
+def test_wheel(session: nox.Session):
+    session.notify("build_wheel")
+    session.notify("test_wheel_with_python-3.8")
+    session.notify("test_wheel_with_python-3.9")
+    session.notify("test_wheel_with_python-3.10")
+    session.notify("test_wheel_with_python-3.11")
+
+
+@nox.session(python=["3.8", "3.9", "3.10", "3.11"])
+def test_wheel_with_python(session: nox.Session):
+    wheel_path = get_wheel(session)
+    session.install("pytest")
+    session.install(str(wheel_path))
+    session.run("pytest", "tests", *session.posargs)
+
+
+@nox.session
+def clean_cache(session: nox.Session):
+    for subtree in session.cache_dir.iterdir():
+        shutil.rmtree(subtree, True)
+
+
+@nox.session
+def build(session: nox.Session):
+    prepare(session)
+    session.install("build[virtualenv]")
+    session.run("python", "-m", "build", "--no-isolation", *session.posargs)
+
+
+@nox.session
+def clean(session: nox.Session):
+    data_dir = _RELATIVE_DATA_DIR
+    session.log(f"rm -r {data_dir}")
+    shutil.rmtree(data_dir, True)
+    session.log("rm -r src/*.egg-info")
+    for egg_tree in pathlib.Path("src").glob("*.egg-info"):
+        shutil.rmtree(egg_tree, True)
+    session.log("rm -r dist")
+    shutil.rmtree("dist", True)
+    session.log("rm -r build")
+    shutil.rmtree("build", True)

.python_package/pyproject.toml

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+[build-system]
+requires = ["setuptools>=64", "wheel"]
+build-backend = "setuptools.build_meta"

.python_package/setup.cfg.in

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+[metadata]
+name = gridtools-cpp
+author = ETH Zurich
+author_email = gridtools@cscs.ch
+license_files = LICENSE # this file is automatically copied from the top level
+long_description = file: README.md
+long_description_content_type = text/markdown; charset=UTF-8
+url = https://gridtools.github.io
+project_urls = 
+	Source Code = https://github.com/GridTools/gridtools
+platforms = any
+version = # leave empty, automatically generated
+classifiers = 
+	Development Status :: 5 - Production/Stable
+	Intended Audience :: Science/Research
+	License :: OSI Approved :: BSD License
+	Operating System :: OS Independent
+	Programming Language :: Python :: 3 :: Only
+	Topic :: Scientific/Engineering :: Atmospheric Science
+	Topic :: Scientific/Engineering :: Mathematics
+	Topic :: Scientific/Engineering :: Physics
+
+[options]
+packages = find_namespace:
+package_dir = 
+	= src
+python_requires = >=3.8
+
+[options.package_data]
+* = 
+	*.hpp
+	*.h
+	*.cmake
+
+[options.packages.find]
+where = src
+exclude = tests
+
+[tools:isort]
+line_length = 100
+
+[flake8]
+max-line-length = 100
+

.python_package/src/gridtools_cpp/__init__.py

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+# GridTools
+#
+# Copyright (c) 2014-2021, ETH Zurich
+# All rights reserved.
+#
+# Please, refer to the LICENSE file in the root directory.
+# SPDX-License-Identifier: BSD-3-Clause
+
+import pathlib
+
+
+_file = pathlib.Path(__file__)
+
+
+def get_cmake_dir() -> pathlib.Path:
+    return _file.parent / "data" / "lib" / "cmake" / "GridTools"
+
+
+def get_include_dir() -> pathlib.Path:
+    return _file.parent / "data" / "include"

.python_package/tests/test_dirs.py

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+# GridTools
+#
+# Copyright (c) 2014-2021, ETH Zurich
+# All rights reserved.
+#
+# Please, refer to the LICENSE file in the root directory.
+# SPDX-License-Identifier: BSD-3-Clause
+
+import gridtools_cpp
+
+
+def test_cmake_dir_contains_gridtools_cmake():
+    main_config_file = gridtools_cpp.get_cmake_dir() / "GridToolsConfig.cmake"
+    assert main_config_file.exists()
+    assert main_config_file.read_text()
+
+
+def test_include_dir_contains_headers():
+    include_path = gridtools_cpp.get_include_dir()
+    assert include_path.exists()
+    assert len(list(include_path.rglob("*.hpp"))) > 0