1198 lines
42 KiB
ReStructuredText
1198 lines
42 KiB
ReStructuredText
:mod:`importlib` -- The implementation of :keyword:`import`
|
|
===========================================================
|
|
|
|
.. module:: importlib
|
|
:synopsis: The 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 the
|
|
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 an 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.
|
|
|
|
.. seealso::
|
|
|
|
:ref:`import`
|
|
The language reference for the :keyword:`import` statement.
|
|
|
|
`Packages specification <http://legacy.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:`451`
|
|
A ModuleSpec Type for the Import System
|
|
|
|
: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 specified package or module
|
|
(e.g. ``pkg.mod``), while :func:`__import__` returns the
|
|
top-level package or module (e.g. ``pkg``).
|
|
|
|
.. versionchanged:: 3.3
|
|
Parent packages are automatically imported.
|
|
|
|
.. 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``.
|
|
|
|
.. deprecated:: 3.4
|
|
Use :func:`importlib.util.find_spec` instead.
|
|
|
|
.. 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
|
|
|
|
.. function:: reload(module)
|
|
|
|
Reload a previously imported *module*. The argument must be a module object,
|
|
so it must have been successfully imported before. This is useful if you
|
|
have edited the module source file using an external editor and want to try
|
|
out the new version without leaving the Python interpreter. The return value
|
|
is the module object (which can be different if re-importing causes a
|
|
different object to be placed in :data:`sys.modules`).
|
|
|
|
When :func:`reload` is executed:
|
|
|
|
* Python module's code is recompiled and the module-level code re-executed,
|
|
defining a new set of objects which are bound to names in the module's
|
|
dictionary by reusing the :term:`loader` which originally loaded the
|
|
module. The ``init`` function of extension modules is not called a second
|
|
time.
|
|
|
|
* As with all other objects in Python the old objects are only reclaimed
|
|
after their reference counts drop to zero.
|
|
|
|
* The names in the module namespace are updated to point to any new or
|
|
changed objects.
|
|
|
|
* Other references to the old objects (such as names external to the module) are
|
|
not rebound to refer to the new objects and must be updated in each namespace
|
|
where they occur if that is desired.
|
|
|
|
There are a number of other caveats:
|
|
|
|
When a module is reloaded, its dictionary (containing the module's global
|
|
variables) is retained. Redefinitions of names will override the old
|
|
definitions, so this is generally not a problem. If the new version of a
|
|
module does not define a name that was defined by the old version, the old
|
|
definition remains. This feature can be used to the module's advantage if it
|
|
maintains a global table or cache of objects --- with a :keyword:`try`
|
|
statement it can test for the table's presence and skip its initialization if
|
|
desired::
|
|
|
|
try:
|
|
cache
|
|
except NameError:
|
|
cache = {}
|
|
|
|
It is generally not very useful to reload built-in or dynamically loaded
|
|
modules. Reloading :mod:`sys`, :mod:`__main__`, :mod:`builtins` and other
|
|
key modules is not recommended. In many cases extension modules are not
|
|
designed to be initialized more than once, and may fail in arbitrary ways
|
|
when reloaded.
|
|
|
|
If a module imports objects from another module using :keyword:`from` ...
|
|
:keyword:`import` ..., calling :func:`reload` for the other module does not
|
|
redefine the objects imported from it --- one way around this is to
|
|
re-execute the :keyword:`from` statement, another is to use :keyword:`import`
|
|
and qualified names (*module.name*) instead.
|
|
|
|
If a module instantiates instances of a class, reloading the module that
|
|
defines the class does not affect the method definitions of the instances ---
|
|
they continue to use the old class definition. The same is true for derived
|
|
classes.
|
|
|
|
.. versionadded:: 3.4
|
|
|
|
|
|
: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_spec(fullname, path, target=None)
|
|
|
|
An abstract method for finding a :term:`spec <module spec>` 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 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.
|
|
|
|
.. versionadded:: 3.4
|
|
|
|
.. method:: find_module(fullname, path)
|
|
|
|
A legacy 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.
|
|
|
|
If :meth:`find_spec` is defined, backwards-compatible functionality is
|
|
provided.
|
|
|
|
.. versionchanged:: 3.4
|
|
Returns ``None`` when called instead of raising
|
|
:exc:`NotImplementedError`. Can use :meth:`find_spec` to provide
|
|
functionality.
|
|
|
|
.. deprecated:: 3.4
|
|
Use :meth:`find_spec` instead.
|
|
|
|
.. 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_spec(fullname, target=None)
|
|
|
|
An abstract method for finding a :term:`spec <module spec>` for
|
|
the specified module. The finder will search for the module only
|
|
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.
|
|
|
|
.. versionadded:: 3.4
|
|
|
|
.. method:: find_loader(fullname)
|
|
|
|
A legacy 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).
|
|
|
|
If :meth:`find_spec` is defined then backwards-compatible functionality is
|
|
provided.
|
|
|
|
.. versionchanged:: 3.4
|
|
Returns ``(None, [])`` instead of raising :exc:`NotImplementedError`.
|
|
Uses :meth:`find_spec` when available to provide functionality.
|
|
|
|
.. deprecated:: 3.4
|
|
Use :meth:`find_spec` instead.
|
|
|
|
.. method:: find_module(fullname)
|
|
|
|
A concrete implementation of :meth:`Finder.find_module` which is
|
|
equivalent to ``self.find_loader(fullname)[0]``.
|
|
|
|
.. deprecated:: 3.4
|
|
Use :meth:`find_spec` instead.
|
|
|
|
.. 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:: create_module(spec)
|
|
|
|
An optional method that returns the module object to use when
|
|
importing a module. create_module() may also return ``None``,
|
|
indicating that the default module creation should take place
|
|
instead.
|
|
|
|
.. versionadded:: 3.4
|
|
|
|
.. method:: exec_module(module)
|
|
|
|
An abstract method that executes the module in its own namespace
|
|
when a module is imported or reloaded. The module should already
|
|
be initialized when exec_module() is called.
|
|
|
|
.. versionadded:: 3.4
|
|
|
|
.. method:: load_module(fullname)
|
|
|
|
A legacy 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 (see :func:`importlib.util.module_for_loader`).
|
|
|
|
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:`__cached__`
|
|
The path to where a compiled version of the module is/should be
|
|
stored (not set when the attribute would be inappropriate).
|
|
|
|
- :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__`.
|
|
|
|
When :meth:`exec_module` is available then backwards-compatible
|
|
functionality is provided.
|
|
|
|
.. versionchanged:: 3.4
|
|
Raise :exc:`ImportError` when called instead of
|
|
:exc:`NotImplementedError`. Functionality provided when
|
|
:meth:`exec_module` is available.
|
|
|
|
.. deprecated:: 3.4
|
|
The recommended API for loading a module is :meth:`exec_module`
|
|
(and optionally :meth:`create_module`). Loaders should implement
|
|
it instead of load_module(). The import machinery takes care of
|
|
all the other responsibilities of load_module() when exec_module()
|
|
is implemented.
|
|
|
|
.. method:: module_repr(module)
|
|
|
|
A legacy 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.
|
|
|
|
.. deprecated:: 3.4
|
|
The import machinery now takes care of this automatically.
|
|
|
|
|
|
.. 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:`OSError` 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:`OSError` 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)
|
|
|
|
Return the code object for a module, or ``None`` if the module does not
|
|
have a code object (as would be the case, for example, for a built-in
|
|
module). Raise an :exc:`ImportError` if loader cannot find the
|
|
requested module.
|
|
|
|
.. note::
|
|
While the method has a default implementation, it is suggested that
|
|
it be overridden if possible for performance.
|
|
|
|
.. index::
|
|
single: universal newlines; importlib.abc.InspectLoader.get_source method
|
|
|
|
.. versionchanged:: 3.4
|
|
No longer abstract and a concrete implementation is provided.
|
|
|
|
.. 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`.
|
|
|
|
.. method:: source_to_code(data, path='<string>')
|
|
|
|
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:: exec_module(module)
|
|
|
|
Implementation of :meth:`Loader.exec_module`.
|
|
|
|
.. versionadded:: 3.4
|
|
|
|
.. method:: load_module(fullname)
|
|
|
|
Implementation of :meth:`Loader.load_module`.
|
|
|
|
.. deprecated:: 3.4
|
|
use :meth:`exec_module` instead.
|
|
|
|
|
|
.. 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()``.
|
|
|
|
.. deprecated:: 3.4
|
|
Use :meth:`Loader.exec_module` instead.
|
|
|
|
.. method:: get_filename(fullname)
|
|
|
|
Returns :attr:`path`.
|
|
|
|
.. method:: get_data(path)
|
|
|
|
Reads *path* as a binary file and returns the bytes from it.
|
|
|
|
|
|
.. 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.
|
|
|
|
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:`OSError` is raised.
|
|
|
|
.. versionadded:: 3.3
|
|
|
|
.. versionchanged:: 3.4
|
|
Raise :exc:`OSError` 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:`OSError` if the path cannot be handled.
|
|
|
|
.. versionchanged:: 3.4
|
|
Raise :exc:`OSError` 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`/:exc:`PermissionError`), do not propagate the
|
|
exception.
|
|
|
|
.. versionchanged:: 3.4
|
|
No longer raises :exc:`NotImplementedError` when called.
|
|
|
|
.. method:: get_code(fullname)
|
|
|
|
Concrete implementation of :meth:`InspectLoader.get_code`.
|
|
|
|
.. method:: exec_module(module)
|
|
|
|
Concrete implementation of :meth:`Loader.exec_module`.
|
|
|
|
.. versionadded:: 3.4
|
|
|
|
.. method:: load_module(fullname)
|
|
|
|
Concrete implementation of :meth:`Loader.load_module`.
|
|
|
|
.. deprecated:: 3.4
|
|
Use :meth:`exec_module` instead.
|
|
|
|
.. 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.
|
|
|
|
.. note::
|
|
Due to limitations in the extension module C-API, for now
|
|
BuiltinImporter does not implement :meth:`Loader.exec_module`.
|
|
|
|
|
|
.. 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_spec(fullname, path=None, target=None)
|
|
|
|
Class method that attempts to find a :term:`spec <module spec>`
|
|
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:`path entry 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.
|
|
|
|
.. versionadded:: 3.4
|
|
|
|
.. classmethod:: find_module(fullname, path=None)
|
|
|
|
A legacy wrapper around :meth:`find_spec`.
|
|
|
|
.. deprecated:: 3.4
|
|
Use :meth:`find_spec` instead.
|
|
|
|
.. classmethod:: invalidate_caches()
|
|
|
|
Calls :meth:`importlib.abc.PathEntryFinder.invalidate_caches` on all
|
|
finders stored in :attr:`sys.path_importer_cache`.
|
|
|
|
.. versionchanged:: 3.4
|
|
Calls objects in :data:`sys.path_hooks` with the current working
|
|
directory for ``''`` (i.e. the empty string).
|
|
|
|
|
|
.. 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 loaders are expected to be callables which accept two arguments of
|
|
the module's name and the path to the file found.
|
|
|
|
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_spec(fullname, target=None)
|
|
|
|
Attempt to find the spec to handle *fullname* within :attr:`path`.
|
|
|
|
.. versionadded:: 3.4
|
|
|
|
.. method:: find_loader(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`.
|
|
|
|
.. method:: load_module(name=None)
|
|
|
|
Concrete implementation of :meth:`importlib.abc.Loader.load_module` where
|
|
specifying the name of the module to load is optional.
|
|
|
|
|
|
.. 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.
|
|
|
|
.. method:: load_module(name=None)
|
|
|
|
Concrete implementation of :meth:`importlib.abc.Loader.load_module` where
|
|
specifying the name of the module to load is optional.
|
|
|
|
|
|
.. class:: ExtensionFileLoader(fullname, path)
|
|
|
|
A concrete implementation of :class:`importlib.abc.ExecutionLoader` 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(name=None)
|
|
|
|
Loads the extension module if and only if *fullname* is the same as
|
|
:attr:`name` or is ``None``.
|
|
|
|
.. note::
|
|
Due to limitations in the extension module C-API, for now
|
|
ExtensionFileLoader does not implement :meth:`Loader.exec_module`.
|
|
|
|
.. 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.
|
|
|
|
.. method:: get_filename(fullname)
|
|
|
|
Returns :attr:`path`.
|
|
|
|
.. versionadded:: 3.4
|
|
|
|
|
|
.. class:: ModuleSpec(name, loader, *, origin=None, loader_state=None, is_package=None)
|
|
|
|
A specification for a module's import-system-related state.
|
|
|
|
.. versionadded:: 3.4
|
|
|
|
.. attribute:: name
|
|
|
|
(``__name__``)
|
|
|
|
A string for the fully-qualified name of the module.
|
|
|
|
.. attribute:: loader
|
|
|
|
(``__loader__``)
|
|
|
|
The loader to use for loading. For namespace packages this should be
|
|
set to None.
|
|
|
|
.. attribute:: origin
|
|
|
|
(``__file__``)
|
|
|
|
Name of the place from which the module is loaded, e.g. "builtin" for
|
|
built-in modules and the filename for modules loaded from source.
|
|
Normally "origin" should be set, but it may be None (the default)
|
|
which indicates it is unspecified.
|
|
|
|
.. attribute:: submodule_search_locations
|
|
|
|
(``__path__``)
|
|
|
|
List of strings for where to find submodules, if a package (None
|
|
otherwise).
|
|
|
|
.. attribute:: loader_state
|
|
|
|
Container of extra module-specific data for use during loading (or
|
|
None).
|
|
|
|
.. attribute:: cached
|
|
|
|
(``__cached__``)
|
|
|
|
String for where the compiled module should be stored (or None).
|
|
|
|
.. attribute:: parent
|
|
|
|
(``__package__``)
|
|
|
|
(Read-only) Fully-qualified name of the package to which the module
|
|
belongs as a submodule (or None).
|
|
|
|
.. attribute:: has_location
|
|
|
|
Boolean indicating whether or not the module's "origin"
|
|
attribute refers to a loadable location.
|
|
|
|
: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`.
|
|
|
|
.. attribute:: MAGIC_NUMBER
|
|
|
|
The bytes which represent the bytecode version number. If you need help with
|
|
loading/writing bytecode then consider :class:`importlib.abc.SourceLoader`.
|
|
|
|
.. versionadded:: 3.4
|
|
|
|
.. function:: cache_from_source(path, debug_override=None)
|
|
|
|
Return the :pep:`3147` path to the byte-compiled file associated with the
|
|
source *path*. For example, if *path* is ``/foo/bar/baz.py`` the return
|
|
value would be ``/foo/bar/__pycache__/baz.cpython-32.pyc`` for Python 3.2.
|
|
The ``cpython-32`` string comes from the current magic tag (see
|
|
:func:`get_tag`; if :attr:`sys.implementation.cache_tag` is not defined then
|
|
:exc:`NotImplementedError` will be raised). The returned path will end in
|
|
``.pyc`` when ``__debug__`` is ``True`` or ``.pyo`` for an optimized Python
|
|
(i.e. ``__debug__`` is ``False``). By passing in ``True`` or ``False`` for
|
|
*debug_override* you can override the system's value for ``__debug__`` for
|
|
extension selection.
|
|
|
|
*path* need not exist.
|
|
|
|
.. versionadded:: 3.4
|
|
|
|
|
|
.. function:: source_from_cache(path)
|
|
|
|
Given the *path* to a :pep:`3147` file name, return the associated source code
|
|
file path. For example, if *path* is
|
|
``/foo/bar/__pycache__/baz.cpython-32.pyc`` the returned path would be
|
|
``/foo/bar/baz.py``. *path* need not exist, however if it does not conform
|
|
to :pep:`3147` format, a ``ValueError`` is raised. If
|
|
:attr:`sys.implementation.cache_tag` is not defined,
|
|
:exc:`NotImplementedError` is raised.
|
|
|
|
.. versionadded:: 3.4
|
|
|
|
.. function:: decode_source(source_bytes)
|
|
|
|
Decode the given bytes representing source code and return it as a string
|
|
with universal newlines (as required by
|
|
:meth:`importlib.abc.InspectLoader.get_source`).
|
|
|
|
.. versionadded:: 3.4
|
|
|
|
.. 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
|
|
|
|
.. function:: find_spec(name, package=None)
|
|
|
|
Find the :term:`spec <module spec>` for a module, optionally relative to
|
|
the specified **package** name. If the module is in :attr:`sys.modules`,
|
|
then ``sys.modules[name].__spec__`` is returned (unless the spec 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 spec is found.
|
|
|
|
If **name** is for a submodule (contains a dot), the parent module is
|
|
automatically imported.
|
|
|
|
**name** and **package** work the same as for :func:`import_module`.
|
|
|
|
.. versionadded:: 3.4
|
|
|
|
.. decorator:: module_for_loader
|
|
|
|
A :term:`decorator` for :meth:`importlib.abc.Loader.load_module`
|
|
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. Regardless of where the
|
|
module came from, :attr:`__loader__` set to **self** and :attr:`__package__`
|
|
is set based on what :meth:`importlib.abc.InspectLoader.is_package` returns
|
|
(if available). These attributes are set unconditionally to support
|
|
reloading.
|
|
|
|
If an exception is raised by the decorated method and a module was added to
|
|
:data:`sys.modules`, then the module 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.
|
|
|
|
.. versionchanged:: 3.3
|
|
:attr:`__loader__` and :attr:`__package__` are automatically set
|
|
(when possible).
|
|
|
|
.. versionchanged:: 3.4
|
|
Set :attr:`__name__`, :attr:`__loader__` :attr:`__package__`
|
|
unconditionally to support reloading.
|
|
|
|
.. deprecated:: 3.4
|
|
The import machinery now directly performs all the functionality
|
|
provided by this function.
|
|
|
|
.. decorator:: set_loader
|
|
|
|
A :term:`decorator` for :meth:`importlib.abc.Loader.load_module`
|
|
to set the :attr:`__loader__`
|
|
attribute on the returned module. 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.
|
|
|
|
.. versionchanged:: 3.4
|
|
Set ``__loader__`` if set to ``None``, as if the attribute does not
|
|
exist.
|
|
|
|
.. deprecated:: 3.4
|
|
The import machinery takes care of this automatically.
|
|
|
|
.. decorator:: set_package
|
|
|
|
A :term:`decorator` for :meth:`importlib.abc.Loader.load_module` to set the :attr:`__package__` attribute on the returned module. If :attr:`__package__`
|
|
is set and has a value other than ``None`` it will not be changed.
|
|
|
|
.. deprecated:: 3.4
|
|
The import machinery takes care of this automatically.
|
|
|
|
.. function:: spec_from_loader(name, loader, *, origin=None, is_package=None)
|
|
|
|
A factory function for creating a :class:`ModuleSpec` instance based
|
|
on a loader. The parameters have the same meaning as they do for
|
|
ModuleSpec. The function uses available :term:`loader` APIs, such as
|
|
:meth:`InspectLoader.is_package`, to fill in any missing
|
|
information on the spec.
|
|
|
|
.. versionadded:: 3.4
|
|
|
|
.. function:: spec_from_file_location(name, location, *, loader=None, submodule_search_locations=None)
|
|
|
|
A factory function for creating a :class:`ModuleSpec` instance based
|
|
on the path to a file. Missing information will be filled in on the
|
|
spec by making use of loader APIs and by the implication that the
|
|
module will be file-based.
|
|
|
|
.. versionadded:: 3.4
|