Rename proposed files from .pkg into .pth. Drop
claims that this extends the .pkg mechanism.
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pep-0382.txt
45
pep-0382.txt
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@ -49,8 +49,8 @@ invoked independent of which portion of the package gets imported
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first. As a consequence, the package's ``__init__.py`` cannot
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practically define any names as it depends on the order of the package
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fragments on sys.path which portion is imported first. As a special
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feature, extend_path reads files named ``*.pkg`` which allow to
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declare additional portions.
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feature, extend_path reads files named ``<packagename>.pkg`` which
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allow to declare additional portions.
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setuptools provides a similar function pkg_resources.declare_namespace
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that is used in the form::
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@ -91,29 +91,27 @@ Specification
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Rather than using an imperative mechanism for importing packages, a
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declarative approach is proposed here, as an extension to the existing
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``*.pkg`` mechanism.
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``*.pth`` mechanism available on the top-level python path.
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The import statement is extended so that it directly considers ``*.pkg``
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files during import; a directory is considered a package if it either
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contains a file named __init__.py, or a file whose name ends with
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".pkg".
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The import statement is extended so that it directly considers
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``*.pth`` files during import; a directory is considered a package if
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it either contains a file named __init__.py, or a file whose name ends
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with ".pth". Unlike .pth files on the top level, lines starting with
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"import" are not supported in per-package .pth files.
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In addition, the format of the ``*.pkg`` file is extended: a line with
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In addition, the format of the ``*.pth`` file is extended: a line with
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the single character ``*`` indicates that the entire sys.path will
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be searched for portions of the namespace package at the time the
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namespace packages is imported.
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Importing a package will immediately compute the package's __path__;
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the ``*.pkg`` files are not considered anymore after the initial import.
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If a ``*.pkg`` package contains an asterisk, this asterisk is prepended
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to the package's __path__ to indicate that the package is a namespace
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package (and that thus further extensions to sys.path might also
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want to extend __path__). At most one such asterisk gets prepended
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to the path. In addition, the (possibly dotted) names of all namespace
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packages are added to the set sys.namespace_packages.
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extend_path will be extended to recognize namespace packages according
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to this PEP, and avoid adding directories twice to __path__.
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the ``*.pth`` files are not considered anymore after the initial
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import. If a ``*.pth`` package contains an asterisk, this asterisk is
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prepended to the package's __path__ to indicate that the package is a
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namespace package (and that thus further extensions to sys.path might
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also want to extend __path__). At most one such asterisk gets
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prepended to the path. In addition, the (possibly dotted) names of all
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namespace packages are added to the set sys.namespace_packages.
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No other change to the importing mechanism is made; searching modules
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(including __init__.py) will continue to stop at the first module
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@ -122,22 +120,22 @@ this:
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1. sys.path is search for a directory foo, or a file foo.<ext>.
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If a file is found, it is treated as a module, and imported.
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2. if it is a directory, it checks for \*.pkg files. If it finds
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2. if it is a directory, it checks for \*.pth files. If it finds
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any, a package is created, and its __path__ is extended.
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3. The __init__ module is imported; this import will search the
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__path__ that got computed already.
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4. If neither a \*.pkg file nor an __init__.py was found, the
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4. If neither a \*.pth file nor an __init__.py was found, the
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directory is skipped, and search for the module/package
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continues.
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Discussion
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==========
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With the addition of ``*.pkg`` files to the import mechanism, namespace
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With the addition of ``*.pth`` files to the import mechanism, namespace
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packages can stop filling out the namespace package's __init__.py.
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As a consequence, extend_path and declare_namespace become obsolete.
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It is recommended that distributions put a file <distribution>.pkg
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It is recommended that distributions put a file <distribution>.pth
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into their namespace packages, with a single asterisk. This allows
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vendor packages to install multiple portions of namespace package
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into a single directory, with no risk of overlapping files.
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@ -160,9 +158,6 @@ having users and tools starting to special-case 2.7). Prospective
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users of this feature are encouraged to comment on this particular
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question.
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It also has been proposed to rename the extension from .pkg to
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something else.
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Copyright
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=========
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