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Editing: miscellaneous.rst
.. _Automatic Resource Extraction: Automatic Resource Extraction ----------------------------- If you are using tools that expect your resources to be "real" files, or your project includes non-extension native libraries or other files that your C extensions expect to be able to access, you may need to list those files in the ``eager_resources`` argument to ``setup()``, so that the files will be extracted together, whenever a C extension in the project is imported. This is especially important if your project includes shared libraries *other* than distutils-built C extensions, and those shared libraries use file extensions other than ``.dll``, ``.so``, or ``.dylib``, which are the extensions that setuptools 0.6a8 and higher automatically detects as shared libraries and adds to the ``native_libs.txt`` file for you. Any shared libraries whose names do not end with one of those extensions should be listed as ``eager_resources``, because they need to be present in the filesystem when he C extensions that link to them are used. The ``pkg_resources`` runtime for compressed packages will automatically extract *all* C extensions and ``eager_resources`` at the same time, whenever *any* C extension or eager resource is requested via the ``resource_filename()`` API. (C extensions are imported using ``resource_filename()`` internally.) This ensures that C extensions will see all of the "real" files that they expect to see. Note also that you can list directory resource names in ``eager_resources`` as well, in which case the directory's contents (including subdirectories) will be extracted whenever any C extension or eager resource is requested. Please note that if you're not sure whether you need to use this argument, you don't! It's really intended to support projects with lots of non-Python dependencies and as a last resort for crufty projects that can't otherwise handle being compressed. If your package is pure Python, Python plus data files, or Python plus C, you really don't need this. You've got to be using either C or an external program that needs "real" files in your project before there's any possibility of ``eager_resources`` being relevant to your project. Defining Additional Metadata ---------------------------- Some extensible applications and frameworks may need to define their own kinds of metadata to include in eggs, which they can then access using the ``pkg_resources`` metadata APIs. Ordinarily, this is done by having plugin developers include additional files in their ``ProjectName.egg-info`` directory. However, since it can be tedious to create such files by hand, you may want to create a distutils extension that will create the necessary files from arguments to ``setup()``, in much the same way that ``setuptools`` does for many of the ``setup()`` arguments it adds. See the section below on :ref:`Creating ``distutils\`\` Extensions` for more details, especially the subsection on :ref:`Adding new EGG-INFO Files`. Setting the ``zip_safe`` flag ----------------------------- For some use cases (such as bundling as part of a larger application), Python packages may be run directly from a zip file. Not all packages, however, are capable of running in compressed form, because they may expect to be able to access either source code or data files as normal operating system files. So, ``setuptools`` can install your project as a zipfile or a directory, and its default choice is determined by the project's ``zip_safe`` flag. You can pass a True or False value for the ``zip_safe`` argument to the ``setup()`` function, or you can omit it. If you omit it, the ``bdist_egg`` command will analyze your project's contents to see if it can detect any conditions that would prevent it from working in a zipfile. It will output notices to the console about any such conditions that it finds. Currently, this analysis is extremely conservative: it will consider the project unsafe if it contains any C extensions or datafiles whatsoever. This does *not* mean that the project can't or won't work as a zipfile! It just means that the ``bdist_egg`` authors aren't yet comfortable asserting that the project *will* work. If the project contains no C or data files, and does no ``__file__`` or ``__path__`` introspection or source code manipulation, then there is an extremely solid chance the project will work when installed as a zipfile. (And if the project uses ``pkg_resources`` for all its data file access, then C extensions and other data files shouldn't be a problem at all. See the :ref:`Accessing Data Files at Runtime` section above for more information.) However, if ``bdist_egg`` can't be *sure* that your package will work, but you've checked over all the warnings it issued, and you are either satisfied it *will* work (or if you want to try it for yourself), then you should set ``zip_safe`` to ``True`` in your ``setup()`` call. If it turns out that it doesn't work, you can always change it to ``False``, which will force ``setuptools`` to install your project as a directory rather than as a zipfile. In the future, as we gain more experience with different packages and become more satisfied with the robustness of the ``pkg_resources`` runtime, the "zip safety" analysis may become less conservative. However, we strongly recommend that you determine for yourself whether your project functions correctly when installed as a zipfile, correct any problems if you can, and then make an explicit declaration of ``True`` or ``False`` for the ``zip_safe`` flag, so that it will not be necessary for ``bdist_egg`` to try to guess whether your project can work as a zipfile.
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