mirror of https://github.com/python/cpython
852 lines
30 KiB
ReStructuredText
852 lines
30 KiB
ReStructuredText
:mod:`importlib` -- An implementation of :keyword:`import`
|
|
==========================================================
|
|
|
|
.. module:: importlib
|
|
:synopsis: An implementation of the import machinery.
|
|
|
|
.. moduleauthor:: Brett Cannon <brett@python.org>
|
|
.. sectionauthor:: Brett Cannon <brett@python.org>
|
|
|
|
.. versionadded:: 3.1
|
|
|
|
|
|
Introduction
|
|
------------
|
|
|
|
The purpose of the :mod:`importlib` package is two-fold. One is to provide an
|
|
implementation of the :keyword:`import` statement (and thus, by extension, the
|
|
:func:`__import__` function) in Python source code. This provides an
|
|
implementation of :keyword:`import` which is portable to any Python
|
|
interpreter. This also provides a reference implementation which is easier to
|
|
comprehend than one implemented in a programming language other than Python.
|
|
|
|
Two, the components to implement :keyword:`import` are exposed in this
|
|
package, making it easier for users to create their own custom objects (known
|
|
generically as an :term:`importer`) to participate in the import process.
|
|
Details on custom importers can be found in :pep:`302`.
|
|
|
|
.. seealso::
|
|
|
|
:ref:`import`
|
|
The language reference for the :keyword:`import` statement.
|
|
|
|
`Packages specification <http://www.python.org/doc/essays/packages.html>`__
|
|
Original specification of packages. Some semantics have changed since
|
|
the writing of this document (e.g. redirecting based on ``None``
|
|
in :data:`sys.modules`).
|
|
|
|
The :func:`.__import__` function
|
|
The :keyword:`import` statement is syntactic sugar for this function.
|
|
|
|
:pep:`235`
|
|
Import on Case-Insensitive Platforms
|
|
|
|
:pep:`263`
|
|
Defining Python Source Code Encodings
|
|
|
|
:pep:`302`
|
|
New Import Hooks
|
|
|
|
:pep:`328`
|
|
Imports: Multi-Line and Absolute/Relative
|
|
|
|
:pep:`366`
|
|
Main module explicit relative imports
|
|
|
|
:pep:`3120`
|
|
Using UTF-8 as the Default Source Encoding
|
|
|
|
:pep:`3147`
|
|
PYC Repository Directories
|
|
|
|
|
|
Functions
|
|
---------
|
|
|
|
.. function:: __import__(name, globals=None, locals=None, fromlist=(), level=0)
|
|
|
|
An implementation of the built-in :func:`__import__` function.
|
|
|
|
.. function:: import_module(name, package=None)
|
|
|
|
Import a module. The *name* argument specifies what module to
|
|
import in absolute or relative terms
|
|
(e.g. either ``pkg.mod`` or ``..mod``). If the name is
|
|
specified in relative terms, then the *package* argument must be set to
|
|
the name of the package which is to act as the anchor for resolving the
|
|
package name (e.g. ``import_module('..mod', 'pkg.subpkg')`` will import
|
|
``pkg.mod``).
|
|
|
|
The :func:`import_module` function acts as a simplifying wrapper around
|
|
:func:`importlib.__import__`. This means all semantics of the function are
|
|
derived from :func:`importlib.__import__`, including requiring the package
|
|
from which an import is occurring to have been previously imported
|
|
(i.e., *package* must already be imported). The most important difference
|
|
is that :func:`import_module` returns the most nested package or module
|
|
that was imported (e.g. ``pkg.mod``), while :func:`__import__` returns the
|
|
top-level package or module (e.g. ``pkg``).
|
|
|
|
.. function:: find_loader(name, path=None)
|
|
|
|
Find the loader for a module, optionally within the specified *path*. If the
|
|
module is in :attr:`sys.modules`, then ``sys.modules[name].__loader__`` is
|
|
returned (unless the loader would be ``None`` or is not set, in which case
|
|
:exc:`ValueError` is raised). Otherwise a search using :attr:`sys.meta_path`
|
|
is done. ``None`` is returned if no loader is found.
|
|
|
|
A dotted name does not have its parent's implicitly imported as that requires
|
|
loading them and that may not be desired. To properly import a submodule you
|
|
will need to import all parent packages of the submodule and use the correct
|
|
argument to *path*.
|
|
|
|
.. versionadded:: 3.3
|
|
|
|
.. versionchanged:: 3.4
|
|
If ``__loader__`` is not set, raise :exc:`ValueError`, just like when the
|
|
attribute is set to ``None``.
|
|
|
|
.. function:: invalidate_caches()
|
|
|
|
Invalidate the internal caches of finders stored at
|
|
:data:`sys.meta_path`. If a finder implements ``invalidate_caches()`` then it
|
|
will be called to perform the invalidation. This function should be called
|
|
if any modules are created/installed while your program is running to
|
|
guarantee all finders will notice the new module's existence.
|
|
|
|
.. versionadded:: 3.3
|
|
|
|
|
|
:mod:`importlib.abc` -- Abstract base classes related to import
|
|
---------------------------------------------------------------
|
|
|
|
.. module:: importlib.abc
|
|
:synopsis: Abstract base classes related to import
|
|
|
|
The :mod:`importlib.abc` module contains all of the core abstract base classes
|
|
used by :keyword:`import`. Some subclasses of the core abstract base classes
|
|
are also provided to help in implementing the core ABCs.
|
|
|
|
ABC hierarchy::
|
|
|
|
object
|
|
+-- Finder (deprecated)
|
|
| +-- MetaPathFinder
|
|
| +-- PathEntryFinder
|
|
+-- Loader
|
|
+-- ResourceLoader --------+
|
|
+-- InspectLoader |
|
|
+-- ExecutionLoader --+
|
|
+-- FileLoader
|
|
+-- SourceLoader
|
|
|
|
|
|
.. class:: Finder
|
|
|
|
An abstract base class representing a :term:`finder`.
|
|
|
|
.. deprecated:: 3.3
|
|
Use :class:`MetaPathFinder` or :class:`PathEntryFinder` instead.
|
|
|
|
.. method:: find_module(fullname, path=None)
|
|
|
|
An abstact method for finding a :term:`loader` for the specified
|
|
module. Originally specified in :pep:`302`, this method was meant
|
|
for use in :data:`sys.meta_path` and in the path-based import subsystem.
|
|
|
|
.. versionchanged:: 3.4
|
|
Returns ``None`` when called instead of raising
|
|
:exc:`NotImplementedError`.
|
|
|
|
|
|
.. class:: MetaPathFinder
|
|
|
|
An abstract base class representing a :term:`meta path finder`. For
|
|
compatibility, this is a subclass of :class:`Finder`.
|
|
|
|
.. versionadded:: 3.3
|
|
|
|
.. method:: find_module(fullname, path)
|
|
|
|
An abstract method for finding a :term:`loader` for the specified
|
|
module. If this is a top-level import, *path* will be ``None``.
|
|
Otherwise, this is a search for a subpackage or module and *path*
|
|
will be the value of :attr:`__path__` from the parent
|
|
package. If a loader cannot be found, ``None`` is returned.
|
|
|
|
.. versionchanged:: 3.4
|
|
Returns ``None`` when called instead of raising
|
|
:exc:`NotImplementedError`.
|
|
|
|
.. method:: invalidate_caches()
|
|
|
|
An optional method which, when called, should invalidate any internal
|
|
cache used by the finder. Used by :func:`importlib.invalidate_caches`
|
|
when invalidating the caches of all finders on :data:`sys.meta_path`.
|
|
|
|
.. versionchanged:: 3.4
|
|
Returns ``None`` when called instead of ``NotImplemented``.
|
|
|
|
|
|
.. class:: PathEntryFinder
|
|
|
|
An abstract base class representing a :term:`path entry finder`. Though
|
|
it bears some similarities to :class:`MetaPathFinder`, ``PathEntryFinder``
|
|
is meant for use only within the path-based import subsystem provided
|
|
by :class:`PathFinder`. This ABC is a subclass of :class:`Finder` for
|
|
compatibility reasons only.
|
|
|
|
.. versionadded:: 3.3
|
|
|
|
.. method:: find_loader(fullname)
|
|
|
|
An abstract method for finding a :term:`loader` for the specified
|
|
module. Returns a 2-tuple of ``(loader, portion)`` where ``portion``
|
|
is a sequence of file system locations contributing to part of a namespace
|
|
package. The loader may be ``None`` while specifying ``portion`` to
|
|
signify the contribution of the file system locations to a namespace
|
|
package. An empty list can be used for ``portion`` to signify the loader
|
|
is not part of a namespace package. If ``loader`` is ``None`` and
|
|
``portion`` is the empty list then no loader or location for a namespace
|
|
package were found (i.e. failure to find anything for the module).
|
|
|
|
.. versionchanged:: 3.4
|
|
Returns ``(None, [])`` instead of raising :exc:`NotImplementedError`.
|
|
|
|
.. method:: find_module(fullname)
|
|
|
|
A concrete implementation of :meth:`Finder.find_module` which is
|
|
equivalent to ``self.find_loader(fullname)[0]``.
|
|
|
|
.. method:: invalidate_caches()
|
|
|
|
An optional method which, when called, should invalidate any internal
|
|
cache used by the finder. Used by :meth:`PathFinder.invalidate_caches`
|
|
when invalidating the caches of all cached finders.
|
|
|
|
|
|
.. class:: Loader
|
|
|
|
An abstract base class for a :term:`loader`.
|
|
See :pep:`302` for the exact definition for a loader.
|
|
|
|
.. method:: load_module(fullname)
|
|
|
|
An abstract method for loading a module. If the module cannot be
|
|
loaded, :exc:`ImportError` is raised, otherwise the loaded module is
|
|
returned.
|
|
|
|
If the requested module already exists in :data:`sys.modules`, that
|
|
module should be used and reloaded.
|
|
Otherwise the loader should create a new module and insert it into
|
|
:data:`sys.modules` before any loading begins, to prevent recursion
|
|
from the import. If the loader inserted a module and the load fails, it
|
|
must be removed by the loader from :data:`sys.modules`; modules already
|
|
in :data:`sys.modules` before the loader began execution should be left
|
|
alone. The :func:`importlib.util.module_for_loader` decorator handles
|
|
all of these details.
|
|
|
|
The loader should set several attributes on the module.
|
|
(Note that some of these attributes can change when a module is
|
|
reloaded.)
|
|
|
|
- :attr:`__name__`
|
|
The name of the module.
|
|
|
|
- :attr:`__file__`
|
|
The path to where the module data is stored (not set for built-in
|
|
modules).
|
|
|
|
- :attr:`__path__`
|
|
A list of strings specifying the search path within a
|
|
package. This attribute is not set on modules.
|
|
|
|
- :attr:`__package__`
|
|
The parent package for the module/package. If the module is
|
|
top-level then it has a value of the empty string. The
|
|
:func:`importlib.util.module_for_loader` decorator can handle the
|
|
details for :attr:`__package__`.
|
|
|
|
- :attr:`__loader__`
|
|
The loader used to load the module. The
|
|
:func:`importlib.util.module_for_loader` decorator can handle the
|
|
details for :attr:`__package__`.
|
|
|
|
.. versionchanged:: 3.4
|
|
Raise :exc:`ImportError` when called instead of
|
|
:exc:`NotImplementedError`.
|
|
|
|
.. method:: module_repr(module)
|
|
|
|
An optional method which when implemented calculates and returns the
|
|
given module's repr, as a string. The module type's default repr() will
|
|
use the result of this method as appropriate.
|
|
|
|
.. versionadded:: 3.3
|
|
|
|
.. versionchanged:: 3.4
|
|
Made optional instead of an abstractmethod.
|
|
|
|
|
|
.. class:: ResourceLoader
|
|
|
|
An abstract base class for a :term:`loader` which implements the optional
|
|
:pep:`302` protocol for loading arbitrary resources from the storage
|
|
back-end.
|
|
|
|
.. method:: get_data(path)
|
|
|
|
An abstract method to return the bytes for the data located at *path*.
|
|
Loaders that have a file-like storage back-end
|
|
that allows storing arbitrary data
|
|
can implement this abstract method to give direct access
|
|
to the data stored. :exc:`IOError` is to be raised if the *path* cannot
|
|
be found. The *path* is expected to be constructed using a module's
|
|
:attr:`__file__` attribute or an item from a package's :attr:`__path__`.
|
|
|
|
.. versionchanged:: 3.4
|
|
Raises :exc:`IOError` instead of :exc:`NotImplementedError`.
|
|
|
|
|
|
.. class:: InspectLoader
|
|
|
|
An abstract base class for a :term:`loader` which implements the optional
|
|
:pep:`302` protocol for loaders that inspect modules.
|
|
|
|
.. method:: get_code(fullname)
|
|
|
|
An abstract method to return the :class:`code` object for a module.
|
|
``None`` is returned if the module does not have a code object
|
|
(e.g. built-in module). :exc:`ImportError` is raised if loader cannot
|
|
find the requested module.
|
|
|
|
.. index::
|
|
single: universal newlines; importlib.abc.InspectLoader.get_source method
|
|
|
|
.. versionchanged:: 3.4
|
|
Raises :exc:`ImportError` instead of :exc:`NotImplementedError`.
|
|
|
|
.. method:: get_source(fullname)
|
|
|
|
An abstract method to return the source of a module. It is returned as
|
|
a text string using :term:`universal newlines`, translating all
|
|
recognized line separators into ``'\n'`` characters. Returns ``None``
|
|
if no source is available (e.g. a built-in module). Raises
|
|
:exc:`ImportError` if the loader cannot find the module specified.
|
|
|
|
.. versionchanged:: 3.4
|
|
Raises :exc:`ImportError` instead of :exc:`NotImplementedError`.
|
|
|
|
.. method:: is_package(fullname)
|
|
|
|
An abstract method to return a true value if the module is a package, a
|
|
false value otherwise. :exc:`ImportError` is raised if the
|
|
:term:`loader` cannot find the module.
|
|
|
|
.. versionchanged:: 3.4
|
|
Raises :exc:`ImportError` instead of :exc:`NotImplementedError`.
|
|
|
|
|
|
.. class:: ExecutionLoader
|
|
|
|
An abstract base class which inherits from :class:`InspectLoader` that,
|
|
when implemented, helps a module to be executed as a script. The ABC
|
|
represents an optional :pep:`302` protocol.
|
|
|
|
.. method:: get_filename(fullname)
|
|
|
|
An abstract method that is to return the value of :attr:`__file__` for
|
|
the specified module. If no path is available, :exc:`ImportError` is
|
|
raised.
|
|
|
|
If source code is available, then the method should return the path to
|
|
the source file, regardless of whether a bytecode was used to load the
|
|
module.
|
|
|
|
.. versionchanged:: 3.4
|
|
Raises :exc:`ImportError` instead of :exc:`NotImplementedError`.
|
|
|
|
|
|
.. class:: FileLoader(fullname, path)
|
|
|
|
An abstract base class which inherits from :class:`ResourceLoader` and
|
|
:class:`ExecutionLoader`, providing concrete implementations of
|
|
:meth:`ResourceLoader.get_data` and :meth:`ExecutionLoader.get_filename`.
|
|
|
|
The *fullname* argument is a fully resolved name of the module the loader is
|
|
to handle. The *path* argument is the path to the file for the module.
|
|
|
|
.. versionadded:: 3.3
|
|
|
|
.. attribute:: name
|
|
|
|
The name of the module the loader can handle.
|
|
|
|
.. attribute:: path
|
|
|
|
Path to the file of the module.
|
|
|
|
.. method:: load_module(fullname)
|
|
|
|
Calls super's ``load_module()``.
|
|
|
|
.. method:: get_filename(fullname)
|
|
|
|
Returns :attr:`path`.
|
|
|
|
.. method:: get_data(path)
|
|
|
|
Returns the open, binary file for *path*.
|
|
|
|
|
|
.. class:: SourceLoader
|
|
|
|
An abstract base class for implementing source (and optionally bytecode)
|
|
file loading. The class inherits from both :class:`ResourceLoader` and
|
|
:class:`ExecutionLoader`, requiring the implementation of:
|
|
|
|
* :meth:`ResourceLoader.get_data`
|
|
* :meth:`ExecutionLoader.get_filename`
|
|
Should only return the path to the source file; sourceless
|
|
loading is not supported (see :class:`SourcelessLoader` if that
|
|
functionality is required)
|
|
|
|
The abstract methods defined by this class are to add optional bytecode
|
|
file support. Not implementing these optional methods (or causing them to
|
|
raise :exc:`NotImplementedError`) causes the loader to
|
|
only work with source code. Implementing the methods allows the loader to
|
|
work with source *and* bytecode files; it does not allow for *sourceless*
|
|
loading where only bytecode is provided. Bytecode files are an
|
|
optimization to speed up loading by removing the parsing step of Python's
|
|
compiler, and so no bytecode-specific API is exposed.
|
|
|
|
.. method:: path_stats(path)
|
|
|
|
Optional abstract method which returns a :class:`dict` containing
|
|
metadata about the specifed path. Supported dictionary keys are:
|
|
|
|
- ``'mtime'`` (mandatory): an integer or floating-point number
|
|
representing the modification time of the source code;
|
|
- ``'size'`` (optional): the size in bytes of the source code.
|
|
|
|
Any other keys in the dictionary are ignored, to allow for future
|
|
extensions. If the path cannot be handled, :exc:`IOError` is raised.
|
|
|
|
.. versionadded:: 3.3
|
|
|
|
.. versionchanged:: 3.4
|
|
Raise :exc:`IOError` instead of :exc:`NotImplementedError`.
|
|
|
|
.. method:: path_mtime(path)
|
|
|
|
Optional abstract method which returns the modification time for the
|
|
specified path.
|
|
|
|
.. deprecated:: 3.3
|
|
This method is deprecated in favour of :meth:`path_stats`. You don't
|
|
have to implement it, but it is still available for compatibility
|
|
purposes. Raise :exc:`IOError` if the path cannot be handled.
|
|
|
|
.. versionchanged:: 3.4
|
|
Raise :exc:`IOError` instead of :exc:`NotImplementedError`.
|
|
|
|
.. method:: set_data(path, data)
|
|
|
|
Optional abstract method which writes the specified bytes to a file
|
|
path. Any intermediate directories which do not exist are to be created
|
|
automatically.
|
|
|
|
When writing to the path fails because the path is read-only
|
|
(:attr:`errno.EACCES`), do not propagate the exception.
|
|
|
|
.. versionchanged:: 3.4
|
|
No longer raises :exc:`NotImplementedError` when called.
|
|
|
|
.. method:: source_to_code(data, path)
|
|
|
|
Create a code object from Python source.
|
|
|
|
The *data* argument can be whatever the :func:`compile` function
|
|
supports (i.e. string or bytes). The *path* argument should be
|
|
the "path" to where the source code originated from, which can be an
|
|
abstract concept (e.g. location in a zip file).
|
|
|
|
.. versionadded:: 3.4
|
|
|
|
.. method:: get_code(fullname)
|
|
|
|
Concrete implementation of :meth:`InspectLoader.get_code`.
|
|
|
|
.. method:: load_module(fullname)
|
|
|
|
Concrete implementation of :meth:`Loader.load_module`.
|
|
|
|
.. method:: get_source(fullname)
|
|
|
|
Concrete implementation of :meth:`InspectLoader.get_source`.
|
|
|
|
.. method:: is_package(fullname)
|
|
|
|
Concrete implementation of :meth:`InspectLoader.is_package`. A module
|
|
is determined to be a package if its file path (as provided by
|
|
:meth:`ExecutionLoader.get_filename`) is a file named
|
|
``__init__`` when the file extension is removed **and** the module name
|
|
itself does not end in ``__init__``.
|
|
|
|
|
|
:mod:`importlib.machinery` -- Importers and path hooks
|
|
------------------------------------------------------
|
|
|
|
.. module:: importlib.machinery
|
|
:synopsis: Importers and path hooks
|
|
|
|
This module contains the various objects that help :keyword:`import`
|
|
find and load modules.
|
|
|
|
.. attribute:: SOURCE_SUFFIXES
|
|
|
|
A list of strings representing the recognized file suffixes for source
|
|
modules.
|
|
|
|
.. versionadded:: 3.3
|
|
|
|
.. attribute:: DEBUG_BYTECODE_SUFFIXES
|
|
|
|
A list of strings representing the file suffixes for non-optimized bytecode
|
|
modules.
|
|
|
|
.. versionadded:: 3.3
|
|
|
|
.. attribute:: OPTIMIZED_BYTECODE_SUFFIXES
|
|
|
|
A list of strings representing the file suffixes for optimized bytecode
|
|
modules.
|
|
|
|
.. versionadded:: 3.3
|
|
|
|
.. attribute:: BYTECODE_SUFFIXES
|
|
|
|
A list of strings representing the recognized file suffixes for bytecode
|
|
modules. Set to either :attr:`DEBUG_BYTECODE_SUFFIXES` or
|
|
:attr:`OPTIMIZED_BYTECODE_SUFFIXES` based on whether ``__debug__`` is true.
|
|
|
|
.. versionadded:: 3.3
|
|
|
|
.. attribute:: EXTENSION_SUFFIXES
|
|
|
|
A list of strings representing the recognized file suffixes for
|
|
extension modules.
|
|
|
|
.. versionadded:: 3.3
|
|
|
|
.. function:: all_suffixes()
|
|
|
|
Returns a combined list of strings representing all file suffixes for
|
|
modules recognized by the standard import machinery. This is a
|
|
helper for code which simply needs to know if a filesystem path
|
|
potentially refers to a module without needing any details on the kind
|
|
of module (for example, :func:`inspect.getmodulename`)
|
|
|
|
.. versionadded:: 3.3
|
|
|
|
|
|
.. class:: BuiltinImporter
|
|
|
|
An :term:`importer` for built-in modules. All known built-in modules are
|
|
listed in :data:`sys.builtin_module_names`. This class implements the
|
|
:class:`importlib.abc.MetaPathFinder` and
|
|
:class:`importlib.abc.InspectLoader` ABCs.
|
|
|
|
Only class methods are defined by this class to alleviate the need for
|
|
instantiation.
|
|
|
|
|
|
.. class:: FrozenImporter
|
|
|
|
An :term:`importer` for frozen modules. This class implements the
|
|
:class:`importlib.abc.MetaPathFinder` and
|
|
:class:`importlib.abc.InspectLoader` ABCs.
|
|
|
|
Only class methods are defined by this class to alleviate the need for
|
|
instantiation.
|
|
|
|
|
|
.. class:: WindowsRegistryFinder
|
|
|
|
:term:`Finder` for modules declared in the Windows registry. This class
|
|
implements the :class:`importlib.abc.Finder` ABC.
|
|
|
|
Only class methods are defined by this class to alleviate the need for
|
|
instantiation.
|
|
|
|
.. versionadded:: 3.3
|
|
|
|
|
|
.. class:: PathFinder
|
|
|
|
A :term:`Finder` for :data:`sys.path` and package ``__path__`` attributes.
|
|
This class implements the :class:`importlib.abc.MetaPathFinder` ABC.
|
|
|
|
Only class methods are defined by this class to alleviate the need for
|
|
instantiation.
|
|
|
|
.. classmethod:: find_module(fullname, path=None)
|
|
|
|
Class method that attempts to find a :term:`loader` for the module
|
|
specified by *fullname* on :data:`sys.path` or, if defined, on
|
|
*path*. For each path entry that is searched,
|
|
:data:`sys.path_importer_cache` is checked. If a non-false object is
|
|
found then it is used as the :term:`finder` to look for the module
|
|
being searched for. If no entry is found in
|
|
:data:`sys.path_importer_cache`, then :data:`sys.path_hooks` is
|
|
searched for a finder for the path entry and, if found, is stored in
|
|
:data:`sys.path_importer_cache` along with being queried about the
|
|
module. If no finder is ever found then ``None`` is both stored in
|
|
the cache and returned.
|
|
|
|
.. classmethod:: invalidate_caches()
|
|
|
|
Calls :meth:`importlib.abc.PathEntryFinder.invalidate_caches` on all
|
|
finders stored in :attr:`sys.path_importer_cache`.
|
|
|
|
|
|
.. class:: FileFinder(path, \*loader_details)
|
|
|
|
A concrete implementation of :class:`importlib.abc.PathEntryFinder` which
|
|
caches results from the file system.
|
|
|
|
The *path* argument is the directory for which the finder is in charge of
|
|
searching.
|
|
|
|
The *loader_details* argument is a variable number of 2-item tuples each
|
|
containing a loader and a sequence of file suffixes the loader recognizes.
|
|
|
|
The finder will cache the directory contents as necessary, making stat calls
|
|
for each module search to verify the cache is not outdated. Because cache
|
|
staleness relies upon the granularity of the operating system's state
|
|
information of the file system, there is a potential race condition of
|
|
searching for a module, creating a new file, and then searching for the
|
|
module the new file represents. If the operations happen fast enough to fit
|
|
within the granularity of stat calls, then the module search will fail. To
|
|
prevent this from happening, when you create a module dynamically, make sure
|
|
to call :func:`importlib.invalidate_caches`.
|
|
|
|
.. versionadded:: 3.3
|
|
|
|
.. attribute:: path
|
|
|
|
The path the finder will search in.
|
|
|
|
.. method:: find_module(fullname)
|
|
|
|
Attempt to find the loader to handle *fullname* within :attr:`path`.
|
|
|
|
.. method:: invalidate_caches()
|
|
|
|
Clear out the internal cache.
|
|
|
|
.. classmethod:: path_hook(\*loader_details)
|
|
|
|
A class method which returns a closure for use on :attr:`sys.path_hooks`.
|
|
An instance of :class:`FileFinder` is returned by the closure using the
|
|
path argument given to the closure directly and *loader_details*
|
|
indirectly.
|
|
|
|
If the argument to the closure is not an existing directory,
|
|
:exc:`ImportError` is raised.
|
|
|
|
|
|
.. class:: SourceFileLoader(fullname, path)
|
|
|
|
A concrete implementation of :class:`importlib.abc.SourceLoader` by
|
|
subclassing :class:`importlib.abc.FileLoader` and providing some concrete
|
|
implementations of other methods.
|
|
|
|
.. versionadded:: 3.3
|
|
|
|
.. attribute:: name
|
|
|
|
The name of the module that this loader will handle.
|
|
|
|
.. attribute:: path
|
|
|
|
The path to the source file.
|
|
|
|
.. method:: is_package(fullname)
|
|
|
|
Return true if :attr:`path` appears to be for a package.
|
|
|
|
.. method:: path_stats(path)
|
|
|
|
Concrete implementation of :meth:`importlib.abc.SourceLoader.path_stats`.
|
|
|
|
.. method:: set_data(path, data)
|
|
|
|
Concrete implementation of :meth:`importlib.abc.SourceLoader.set_data`.
|
|
|
|
|
|
.. class:: SourcelessFileLoader(fullname, path)
|
|
|
|
A concrete implementation of :class:`importlib.abc.FileLoader` which can
|
|
import bytecode files (i.e. no source code files exist).
|
|
|
|
Please note that direct use of bytecode files (and thus not source code
|
|
files) inhibits your modules from being usable by all Python
|
|
implementations or new versions of Python which change the bytecode
|
|
format.
|
|
|
|
.. versionadded:: 3.3
|
|
|
|
.. attribute:: name
|
|
|
|
The name of the module the loader will handle.
|
|
|
|
.. attribute:: path
|
|
|
|
The path to the bytecode file.
|
|
|
|
.. method:: is_package(fullname)
|
|
|
|
Determines if the module is a package based on :attr:`path`.
|
|
|
|
.. method:: get_code(fullname)
|
|
|
|
Returns the code object for :attr:`name` created from :attr:`path`.
|
|
|
|
.. method:: get_source(fullname)
|
|
|
|
Returns ``None`` as bytecode files have no source when this loader is
|
|
used.
|
|
|
|
|
|
.. class:: ExtensionFileLoader(fullname, path)
|
|
|
|
A concrete implementation of :class:`importlib.abc.InspectLoader` for
|
|
extension modules.
|
|
|
|
The *fullname* argument specifies the name of the module the loader is to
|
|
support. The *path* argument is the path to the extension module's file.
|
|
|
|
.. versionadded:: 3.3
|
|
|
|
.. attribute:: name
|
|
|
|
Name of the module the loader supports.
|
|
|
|
.. attribute:: path
|
|
|
|
Path to the extension module.
|
|
|
|
.. method:: load_module(fullname)
|
|
|
|
Loads the extension module if and only if *fullname* is the same as
|
|
:attr:`name` or is ``None``.
|
|
|
|
.. method:: is_package(fullname)
|
|
|
|
Returns ``True`` if the file path points to a package's ``__init__``
|
|
module based on :attr:`EXTENSION_SUFFIXES`.
|
|
|
|
.. method:: get_code(fullname)
|
|
|
|
Returns ``None`` as extension modules lack a code object.
|
|
|
|
.. method:: get_source(fullname)
|
|
|
|
Returns ``None`` as extension modules do not have source code.
|
|
|
|
|
|
:mod:`importlib.util` -- Utility code for importers
|
|
---------------------------------------------------
|
|
|
|
.. module:: importlib.util
|
|
:synopsis: Utility code for importers
|
|
|
|
This module contains the various objects that help in the construction of
|
|
an :term:`importer`.
|
|
|
|
.. function:: resolve_name(name, package)
|
|
|
|
Resolve a relative module name to an absolute one.
|
|
|
|
If **name** has no leading dots, then **name** is simply returned. This
|
|
allows for usage such as
|
|
``importlib.util.resolve_name('sys', __package__)`` without doing a
|
|
check to see if the **package** argument is needed.
|
|
|
|
:exc:`ValueError` is raised if **name** is a relative module name but
|
|
package is a false value (e.g. ``None`` or the empty string).
|
|
:exc:`ValueError` is also raised a relative name would escape its containing
|
|
package (e.g. requesting ``..bacon`` from within the ``spam`` package).
|
|
|
|
.. versionadded:: 3.3
|
|
|
|
.. decorator:: module_for_loader
|
|
|
|
A :term:`decorator` for a :term:`loader` method,
|
|
to handle selecting the proper
|
|
module object to load with. The decorated method is expected to have a call
|
|
signature taking two positional arguments
|
|
(e.g. ``load_module(self, module)``) for which the second argument
|
|
will be the module **object** to be used by the loader.
|
|
Note that the decorator will not work on static methods because of the
|
|
assumption of two arguments.
|
|
|
|
The decorated method will take in the **name** of the module to be loaded
|
|
as expected for a :term:`loader`. If the module is not found in
|
|
:data:`sys.modules` then a new one is constructed with its
|
|
:attr:`__name__` attribute set to **name**, :attr:`__loader__` set to
|
|
**self**, and :attr:`__package__` set if
|
|
:meth:`importlib.abc.InspectLoader.is_package` is defined for **self** and
|
|
does not raise :exc:`ImportError` for **name**. If a new module is not
|
|
needed then the module found in :data:`sys.modules` will be passed into the
|
|
method.
|
|
|
|
If an exception is raised by the decorated method and a module was added to
|
|
:data:`sys.modules` it will be removed to prevent a partially initialized
|
|
module from being in left in :data:`sys.modules`. If the module was already
|
|
in :data:`sys.modules` then it is left alone.
|
|
|
|
Use of this decorator handles all the details of which module object a
|
|
loader should initialize as specified by :pep:`302` as best as possible.
|
|
|
|
.. versionchanged:: 3.3
|
|
:attr:`__loader__` and :attr:`__package__` are automatically set
|
|
(when possible).
|
|
|
|
.. decorator:: set_loader
|
|
|
|
A :term:`decorator` for a :term:`loader` method,
|
|
to set the :attr:`__loader__`
|
|
attribute on loaded modules. If the attribute is already set the decorator
|
|
does nothing. It is assumed that the first positional argument to the
|
|
wrapped method (i.e. ``self``) is what :attr:`__loader__` should be set to.
|
|
|
|
.. note::
|
|
|
|
It is recommended that :func:`module_for_loader` be used over this
|
|
decorator as it subsumes this functionality.
|
|
|
|
.. versionchanged:: 3.4
|
|
Set ``__loader__`` if set to ``None``, as if the attribute does not
|
|
exist.
|
|
|
|
|
|
.. decorator:: set_package
|
|
|
|
A :term:`decorator` for a :term:`loader` to set the :attr:`__package__`
|
|
attribute on the module returned by the loader. If :attr:`__package__` is
|
|
set and has a value other than ``None`` it will not be changed.
|
|
Note that the module returned by the loader is what has the attribute
|
|
set on and not the module found in :data:`sys.modules`.
|
|
|
|
Reliance on this decorator is discouraged when it is possible to set
|
|
:attr:`__package__` before importing. By
|
|
setting it beforehand the code for the module is executed with the
|
|
attribute set and thus can be used by global level code during
|
|
initialization.
|
|
|
|
.. note::
|
|
|
|
It is recommended that :func:`module_for_loader` be used over this
|
|
decorator as it subsumes this functionality.
|