.. _minimal: Minimal package layout ====================== This chapter describes a minimal package layout. If you created your repository using the instructions in :ref:`using-the-template`, then your package will already be as described on this page. Read this only if you need to modify any of these files and/or want to understand the files that the template has placed in your repository. To start off, we will take a look at the minimal set of files you will need to create an installable Python package. Once you have set these up, your package directory should look like:: ├── LICENCE ├── my_package │   └── __init__.py ├── pyproject.toml ├── setup.py ├── MANIFEST.in └── README.rst where ``my_package`` is the name of your package. We will now take a look at all of these files in turn. .. _license: ``LICENSE`` ----------- Assuming that you are planning to make your package open source, the most important file you will need to add to your package is an open source license. The Roman SNPIT uses 3-clause BSD license (which is used by may packages in the scientific Python echosystem), and that is already in the ``LICENSE`` file imported from the template. If you have a good reason to want to use a different license, please contact one of the software admins for the PIT. .. _readme: ``README.rst`` -------------- Another important file to include is a README file, which briefly tells users what the package is, and either gives some information about how to install/use it or links to more extensive documentation. We recommend using the `reStructuredText (rst) `_ format for your README as this will ensure that the README gets rendered well online, e.g. on `GitHub `_ or `PyPI `_. .. _package_init: ``my_package/__init__.py`` -------------------------- Python code for your package should live in a sub-directory that has the name of the Python module you want your users to import. This module name should be a valid Python variable name, so cannot start with numbers and cannot include hyphens. Valid package names are ``example`` or ``my_package``. For the rest of this guide, we will assume the name of the module is ``my_package``. A directory structure built from this package template will have a ``__init__.py`` file all in place that may well be all that you need. If you know that you need additional things in your ``__init__.py``, add those things to the one the package template gives you. Among other things, the package template will set it up so that once your package is properly installed, your module will have a `__version__` property that is pulled from tags in the git archive. .. _pyproject: ``pyproject.toml`` ------------------ The ``pyproject.toml`` file is where we will define the metadata about the package. At a minimum, this file should contain the ``[project]`` table (defined by `PEP621 `_) and the ``[build-system]`` table (defined by `PEP518 `__). The ``pyproject.toml`` file provided by the package template will provide most of what you need, so you will seed that much of what is described below is already in place. You may need to add some dependencies to your package. ``[project]`` ^^^^^^^^^^^^^ .. code-block:: toml [project] name = "my-package" description = "My package description" readme = "README.rst" authors = [ { name = "Your Name", email = "your@email.com" } ] license = { text = "BSD 3-Clause License" } dependencies = [ "numpy", "astropy>=3.2", ] dynamic = ["version"] [project.urls] homepage = "https://link-to-your-project" The ``name`` field is the name your package will have on PyPI. It is not necessarily the same as the module name, so in this case we've set the package name to ``my-package`` even though the module name is ``my_package``. However, aside from the case where the package name has a hyphen and the module name has an underscore, we recommend making the package and the module name the same to avoid confusion. Sometimes this is impossible, as a package name may already be used on PyPI, or may otherwise be rejected by PyPI. A good second option is to add a prefix of ``roman-snpit`` to the ``name`` field of your pckage. This is done, for example, in the ``snappl`` package (`cf: the snappl pyproject.toml `_). Note that the version of the package is **not** explicitly defined in the file above, (rather, defined as ``dynamic``), because we are using the `setuptools_scm `_ package to automatically retrieve the latest version from Git tags. See :ref:`releasing` for more information. The ``description`` should be a short one-line sentence that will appear next to your package name on `PyPI `_ when users search for packages. The ``readme`` defines the ``README.rst`` file, which will be rendered nicely on the PyPI page for the package. Finally, the ``dependencies`` section is important since it is where you will be declaring the dependencies for your package. The cleanest way to do this is to specify one package per line, as shown above. You can optionally include version restrictions if needed (as shown with ``astropy>=3.2`` above). If your package has no dependencies then you don't need this option. A complete list of keywords in ``[project]`` can be found in the `Python packaging documentation `_. ``[build-system]`` ^^^^^^^^^^^^^^^^^^ In the previous section we discussed the ``dependencies`` which can be used to declare run-time dependencies for the package, which are dependencies that are needed for the package to import and run correctly. However, your package may have dependencies that are needed to build the package in the first place. For example, the :ref:`setup_py` file will only run correctly if `setuptools `_ is installed. The recommended way to specify build-time dependencies is to define the ``build-system`` table: .. code-block:: toml [build-system] requires = ["setuptools>=45", "wheel", "setuptools_scm[toml]>=6.2"] build-backend = 'setuptools.build_meta' If your package has C extensions that interface with `Numpy `_, you may also need to add Numpy to the above list - see :ref:`extensions` for more details. A complete list of keywords in ``[build-system]`` can be found in `PEP518 `__. ``[tool.setuptools]`` ^^^^^^^^^^^^^^^^^^^^^ .. code-block:: toml [tool.setuptools] zip_safe = false [tool.setuptools.packages.find] The ``zip_safe`` option should be set to ``false`` unless you understand the implications of setting it to ``true`` - this option is most relevant when producing application bundles with Python packages. The ``packages.find`` line can be left as-is - this will automatically determine the Python modules to install based on the presence of ``__init__.py`` files. A complete list of keywords in ``[tool.setuptools]`` can be found in the `setuptools documentation `_. ``[tool.setuptools_scm]`` ^^^^^^^^^^^^^^^^^^^^^^^^^ .. code-block:: toml [tool.setuptools_scm] version_file = "my_package/_version.py" The ``[tool.setuptools_scm]`` table indicates that we want to use the `setuptools_scm `_ package to set the version automatically based on git tags, which will produce version strings such as ``0.13`` for a stable release, or ``0.16.0.dev113+g3d1a8747`` for a developer version. .. _setup_py: ``setup.py`` ------------ The ``setup.py`` file used to be where project metadata was defined, before the advent of ``setup.cfg`` and then PEP621 and PEP517 (``pyproject.toml``). It is no longer necessary to include a ``setup.py`` file in your project, unless you are building C extensions in your code. However, it can increase compatibility with old versions of pip and other packaging tools. The minimal ``setup.py`` file is very simple: .. code-block:: python from setuptools import setup setup() .. _manifest: ``MANIFEST.in`` --------------- The last file needed for a minimal set-up is the ``MANIFEST.in`` file, which declares which files should be included when you release your package (see :ref:`releasing` for more details about how to do this). This file is simplified by using ``setuptools_scm``, as **everything** that is git versioned will be included **by default**. There are likely to be things you want to exclude, such as files generated by the documentation, to do this add:: prune For example a minimal ``MANIFEST.in`` file for a package using ``setuptools_scm`` might look like .. code-block:: text prune build prune docs/_build prune docs/api global-exclude *.pyc *.o which would exclude the autogenerated documentation folders and other build files from the distributions. If you have chosen not to use ``setuptools_scm``, then this file needs to list files not in the module directory and other non-standard files. So given the files we've seen above you would need to include:: include LICENSE include README.rst include pyproject.toml You can find out more about the syntax of this file in `Specifying the files to distribute `_ in the Python documentation.