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-rw-r--r--Doc/library/importlib.rst129
1 files changed, 127 insertions, 2 deletions
diff --git a/Doc/library/importlib.rst b/Doc/library/importlib.rst
index 43b34e9..1a1348f 100644
--- a/Doc/library/importlib.rst
+++ b/Doc/library/importlib.rst
@@ -256,7 +256,7 @@ ABC hierarchy::
module and *path* will be the value of :attr:`__path__` from the
parent package. If a spec cannot be found, ``None`` is returned.
When passed in, ``target`` is a module object that the finder may
- use to make a more educated about what spec to return.
+ use to make a more educated guess about what spec to return.
.. versionadded:: 3.4
@@ -306,7 +306,7 @@ ABC hierarchy::
within the :term:`path entry` to which it is assigned. If a spec
cannot be found, ``None`` is returned. When passed in, ``target``
is a module object that the finder may use to make a more educated
- about what spec to return.
+ guess about what spec to return.
.. versionadded:: 3.4
@@ -921,6 +921,10 @@ find and load modules.
Concrete implementation of :meth:`importlib.abc.Loader.load_module` where
specifying the name of the module to load is optional.
+ .. deprecated:: 3.6
+
+ Use :meth:`importlib.abc.Loader.exec_module` instead.
+
.. class:: SourcelessFileLoader(fullname, path)
@@ -960,6 +964,10 @@ find and load modules.
Concrete implementation of :meth:`importlib.abc.Loader.load_module` where
specifying the name of the module to load is optional.
+ .. deprecated:: 3.6
+
+ Use :meth:`importlib.abc.Loader.exec_module` instead.
+
.. class:: ExtensionFileLoader(fullname, path)
@@ -1300,3 +1308,120 @@ an :term:`importer`.
loader = importlib.machinery.SourceFileLoader
lazy_loader = importlib.util.LazyLoader.factory(loader)
finder = importlib.machinery.FileFinder(path, (lazy_loader, suffixes))
+
+.. _importlib-examples:
+
+Examples
+--------
+
+To programmatically import a module, use :func:`importlib.import_module`.
+::
+
+ import importlib
+
+ itertools = importlib.import_module('itertools')
+
+If you need to find out if a module can be imported without actually doing the
+import, then you should use :func:`importlib.util.find_spec`.
+::
+
+ import importlib.util
+ import sys
+
+ # For illustrative purposes.
+ name = 'itertools'
+
+ spec = importlib.util.find_spec(name)
+ if spec is None:
+ print("can't find the itertools module")
+ else:
+ # If you chose to perform the actual import ...
+ module = importlib.util.module_from_spec(spec)
+ spec.loader.exec_module(module)
+ # Adding the module to sys.modules is optional.
+ sys.modules[name] = module
+
+To import a Python source file directly, use the following recipe
+(Python 3.4 and newer only)::
+
+ import importlib.util
+ import sys
+
+ # For illustrative purposes.
+ import tokenize
+ file_path = tokenize.__file__
+ module_name = tokenize.__name__
+
+ spec = importlib.util.spec_from_file_location(module_name, file_path)
+ module = importlib.util.module_from_spec(spec)
+ spec.loader.exec_module(module)
+ # Optional; only necessary if you want to be able to import the module
+ # by name later.
+ sys.modules[module_name] = module
+
+For deep customizations of import, you typically want to implement an
+:term:`importer`. This means managing both the :term:`finder` and :term:`loader`
+side of things. For finders there are two flavours to choose from depending on
+your needs: a :term:`meta path finder` or a :term:`path entry finder`. The
+former is what you would put on :attr:`sys.meta_path` while the latter is what
+you create using a :term:`path entry hook` on :attr:`sys.path_hooks` which works
+with :attr:`sys.path` entries to potentially create a finder. This example will
+show you how to register your own importers so that import will use them (for
+creating an importer for yourself, read the documentation for the appropriate
+classes defined within this package)::
+
+ import importlib.machinery
+ import sys
+
+ # For illustrative purposes only.
+ SpamMetaPathFinder = importlib.machinery.PathFinder
+ SpamPathEntryFinder = importlib.machinery.FileFinder
+ loader_details = (importlib.machinery.SourceFileLoader,
+ importlib.machinery.SOURCE_SUFFIXES)
+
+ # Setting up a meta path finder.
+ # Make sure to put the finder in the proper location in the list in terms of
+ # priority.
+ sys.meta_path.append(SpamMetaPathFinder)
+
+ # Setting up a path entry finder.
+ # Make sure to put the path hook in the proper location in the list in terms
+ # of priority.
+ sys.path_hooks.append(SpamPathEntryFinder.path_hook(loader_details))
+
+Import itself is implemented in Python code, making it possible to
+expose most of the import machinery through importlib. The following
+helps illustrate the various APIs that importlib exposes by providing an
+approximate implementation of
+:func:`importlib.import_module` (Python 3.4 and newer for the importlib usage,
+Python 3.6 and newer for other parts of the code).
+::
+
+ import importlib.util
+ import sys
+
+ def import_module(name, package=None):
+ """An approximate implementation of import."""
+ absolute_name = importlib.util.resolve_name(name, package)
+ try:
+ return sys.modules[absolute_name]
+ except KeyError:
+ pass
+
+ path = None
+ if '.' in absolute_name:
+ parent_name, _, child_name = absolute_name.rpartition('.')
+ parent_module = import_module(parent_name)
+ path = parent_module.spec.submodule_search_locations
+ for finder in sys.meta_path:
+ spec = finder.find_spec(absolute_name, path)
+ if spec is not None:
+ break
+ else:
+ raise ImportError(f'No module named {absolute_name!r}')
+ module = importlib.util.module_from_spec(spec)
+ spec.loader.exec_module(module)
+ sys.modules[absolute_name] = module
+ if path is not None:
+ setattr(parent_module, child_name, module)
+ return module