31.5. "importlib" – The implementation of "import"
**************************************************

New in version 3.1.


31.5.1. Introduction
====================

The purpose of the "importlib" package is two-fold. One is to provide
the implementation of the "import" statement (and thus, by extension,
the "__import__()" function) in Python source code. This provides an
implementation of "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 "import" are exposed in this package,
making it easier for users to create their own custom objects (known
generically as an *importer*) to participate in the import process.

See also:

  The import statement
     The language reference for the "import" statement.

  Packages specification
     Original specification of packages. Some semantics have changed
     since the writing of this document (e.g. redirecting based on
     "None" in "sys.modules").

  The "__import__()" function
     The "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


31.5.2. Functions
=================

importlib.__import__(name, globals=None, locals=None, fromlist=(), level=0)

   An implementation of the built-in "__import__()" function.

importlib.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 "import_module()" function acts as a simplifying wrapper around
   "importlib.__import__()". This means all semantics of the function
   are derived from "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 "import_module()" returns the
   specified package or module (e.g. "pkg.mod"), while "__import__()"
   returns the top-level package or module (e.g. "pkg").

   Changed in version 3.3: Parent packages are automatically imported.

importlib.find_loader(name, path=None)

   Find the loader for a module, optionally within the specified
   *path*. If the module is in "sys.modules", then
   "sys.modules[name].__loader__" is returned (unless the loader would
   be "None" or is not set, in which case "ValueError" is raised).
   Otherwise a search using "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*.

   New in version 3.3.

   Changed in version 3.4: If "__loader__" is not set, raise
   "ValueError", just like when the attribute is set to "None".

   Deprecated since version 3.4: Use "importlib.util.find_spec()"
   instead.

importlib.invalidate_caches()

   Invalidate the internal caches of finders stored at
   "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.

   New in version 3.3.

importlib.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 "sys.modules").

   When "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 *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 "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 "sys", "__main__", "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 "from" …
   "import" …, calling "reload()" for the other module does not
   redefine the objects imported from it — one way around this is to
   re-execute the "from" statement, another is to use "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.

   New in version 3.4.


31.5.3. "importlib.abc" – Abstract base classes related to import
=================================================================

The "importlib.abc" module contains all of the core abstract base
classes used by "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 importlib.abc.Finder

   An abstract base class representing a *finder*.

   Deprecated since version 3.3: Use "MetaPathFinder" or
   "PathEntryFinder" instead.

   find_module(fullname, path=None)

      An abstact method for finding a *loader* for the specified
      module.  Originally specified in **PEP 302**, this method was
      meant for use in "sys.meta_path" and in the path-based import
      subsystem.

      Changed in version 3.4: Returns "None" when called instead of
      raising "NotImplementedError".

class importlib.abc.MetaPathFinder

   An abstract base class representing a *meta path finder*. For
   compatibility, this is a subclass of "Finder".

   New in version 3.3.

   find_spec(fullname, path, target=None)

      An abstract method for finding a *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 "__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.

      New in version 3.4.

   find_module(fullname, path)

      A legacy method for finding a *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 "__path__" from the parent package. If a loader
      cannot be found, "None" is returned.

      If "find_spec()" is defined, backwards-compatible functionality
      is provided.

      Changed in version 3.4: Returns "None" when called instead of
      raising "NotImplementedError". Can use "find_spec()" to provide
      functionality.

      Deprecated since version 3.4: Use "find_spec()" instead.

   invalidate_caches()

      An optional method which, when called, should invalidate any
      internal cache used by the finder. Used by
      "importlib.invalidate_caches()" when invalidating the caches of
      all finders on "sys.meta_path".

      Changed in version 3.4: Returns "None" when called instead of
      "NotImplemented".

class importlib.abc.PathEntryFinder

   An abstract base class representing a *path entry finder*.  Though
   it bears some similarities to "MetaPathFinder", "PathEntryFinder"
   is meant for use only within the path-based import subsystem
   provided by "PathFinder". This ABC is a subclass of "Finder" for
   compatibility reasons only.

   New in version 3.3.

   find_spec(fullname, target=None)

      An abstract method for finding a *spec* for the specified
      module.  The finder will search for the module only within the
      *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.

      New in version 3.4.

   find_loader(fullname)

      A legacy method for finding a *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 "find_spec()" is defined then backwards-compatible
      functionality is provided.

      Changed in version 3.4: Returns "(None, [])" instead of raising
      "NotImplementedError". Uses "find_spec()" when available to
      provide functionality.

      Deprecated since version 3.4: Use "find_spec()" instead.

   find_module(fullname)

      A concrete implementation of "Finder.find_module()" which is
      equivalent to "self.find_loader(fullname)[0]".

      Deprecated since version 3.4: Use "find_spec()" instead.

   invalidate_caches()

      An optional method which, when called, should invalidate any
      internal cache used by the finder. Used by
      "PathFinder.invalidate_caches()" when invalidating the caches of
      all cached finders.

class importlib.abc.Loader

   An abstract base class for a *loader*. See **PEP 302** for the
   exact definition for a loader.

   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.

      New in version 3.4.

   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.

      New in version 3.4.

   load_module(fullname)

      A legacy method for loading a module. If the module cannot be
      loaded, "ImportError" is raised, otherwise the loaded module is
      returned.

      If the requested module already exists in "sys.modules", that
      module should be used and reloaded. Otherwise the loader should
      create a new module and insert it into "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 "sys.modules"; modules already in
      "sys.modules" before the loader began execution should be left
      alone (see "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):

      * "__name__"

           The name of the module.

      * "__file__"

           The path to where the module data is stored (not set for
           built-in modules).

      * "__cached__"

           The path to where a compiled version of the module
           is/should be stored (not set when the attribute would be
           inappropriate).

      * "__path__"

           A list of strings specifying the search path within a
           package. This attribute is not set on modules.

      * "__package__"

           The parent package for the module/package. If the module is
           top-level then it has a value of the empty string. The
           "importlib.util.module_for_loader()" decorator can handle
           the details for "__package__".

      * "__loader__"

           The loader used to load the module. The
           "importlib.util.module_for_loader()" decorator can handle
           the details for "__package__".

      When "exec_module()" is available then backwards-compatible
      functionality is provided.

      Changed in version 3.4: Raise "ImportError" when called instead
      of "NotImplementedError". Functionality provided when
      "exec_module()" is available.

      Deprecated since version 3.4: The recommended API for loading a
      module is "exec_module()" (and optionally "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.

   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.

      New in version 3.3.

      Changed in version 3.4: Made optional instead of an
      abstractmethod.

      Deprecated since version 3.4: The import machinery now takes
      care of this automatically.

class importlib.abc.ResourceLoader

   An abstract base class for a *loader* which implements the optional
   **PEP 302** protocol for loading arbitrary resources from the
   storage back-end.

   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. "OSError" is to be
      raised if the *path* cannot be found. The *path* is expected to
      be constructed using a module’s "__file__" attribute or an item
      from a package’s "__path__".

      Changed in version 3.4: Raises "OSError" instead of
      "NotImplementedError".

class importlib.abc.InspectLoader

   An abstract base class for a *loader* which implements the optional
   **PEP 302** protocol for loaders that inspect modules.

   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 "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.

      Changed in version 3.4: No longer abstract and a concrete
      implementation is provided.

   get_source(fullname)

      An abstract method to return the source of a module. It is
      returned as a text string using *universal newlines*,
      translating all recognized line separators into "'\n'"
      characters.  Returns "None" if no source is available (e.g. a
      built-in module). Raises "ImportError" if the loader cannot find
      the module specified.

      Changed in version 3.4: Raises "ImportError" instead of
      "NotImplementedError".

   is_package(fullname)

      An abstract method to return a true value if the module is a
      package, a false value otherwise. "ImportError" is raised if the
      *loader* cannot find the module.

      Changed in version 3.4: Raises "ImportError" instead of
      "NotImplementedError".

   source_to_code(data, path='<string>')

      Create a code object from Python source.

      The *data* argument can be whatever the "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).

      New in version 3.4.

   exec_module(module)

      Implementation of "Loader.exec_module()".

      New in version 3.4.

   load_module(fullname)

      Implementation of "Loader.load_module()".

      Deprecated since version 3.4: use "exec_module()" instead.

class importlib.abc.ExecutionLoader

   An abstract base class which inherits from "InspectLoader" that,
   when implemented, helps a module to be executed as a script. The
   ABC represents an optional **PEP 302** protocol.

   get_filename(fullname)

      An abstract method that is to return the value of "__file__" for
      the specified module. If no path is available, "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.

      Changed in version 3.4: Raises "ImportError" instead of
      "NotImplementedError".

class importlib.abc.FileLoader(fullname, path)

   An abstract base class which inherits from "ResourceLoader" and
   "ExecutionLoader", providing concrete implementations of
   "ResourceLoader.get_data()" and "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.

   New in version 3.3.

   name

      The name of the module the loader can handle.

   path

      Path to the file of the module.

   load_module(fullname)

      Calls super’s "load_module()".

      Deprecated since version 3.4: Use "Loader.exec_module()"
      instead.

   get_filename(fullname)

      Returns "path".

   get_data(path)

      Reads *path* as a binary file and returns the bytes from it.

class importlib.abc.SourceLoader

   An abstract base class for implementing source (and optionally
   bytecode) file loading. The class inherits from both
   "ResourceLoader" and "ExecutionLoader", requiring the
   implementation of:

   * "ResourceLoader.get_data()"

   * "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 "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.

   path_stats(path)

      Optional abstract method which returns a "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, "OSError" is
      raised.

      New in version 3.3.

      Changed in version 3.4: Raise "OSError" instead of
      "NotImplementedError".

   path_mtime(path)

      Optional abstract method which returns the modification time for
      the specified path.

      Deprecated since version 3.3: This method is deprecated in
      favour of "path_stats()".  You don’t have to implement it, but
      it is still available for compatibility purposes. Raise
      "OSError" if the path cannot be handled.

      Changed in version 3.4: Raise "OSError" instead of
      "NotImplementedError".

   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
      ("errno.EACCES"/"PermissionError"), do not propagate the
      exception.

      Changed in version 3.4: No longer raises "NotImplementedError"
      when called.

   get_code(fullname)

      Concrete implementation of "InspectLoader.get_code()".

   exec_module(module)

         Concrete implementation of "Loader.exec_module()".

      New in version 3.4.

   load_module(fullname)

      Concrete implementation of "Loader.load_module()".

      Deprecated since version 3.4: Use "exec_module()" instead.

   get_source(fullname)

      Concrete implementation of "InspectLoader.get_source()".

   is_package(fullname)

      Concrete implementation of "InspectLoader.is_package()". A
      module is determined to be a package if its file path (as
      provided by "ExecutionLoader.get_filename()") is a file named
      "__init__" when the file extension is removed **and** the module
      name itself does not end in "__init__".


31.5.4. "importlib.machinery" – Importers and path hooks
========================================================

This module contains the various objects that help "import" find and
load modules.

importlib.machinery.SOURCE_SUFFIXES

   A list of strings representing the recognized file suffixes for
   source modules.

   New in version 3.3.

importlib.machinery.DEBUG_BYTECODE_SUFFIXES

   A list of strings representing the file suffixes for non-optimized
   bytecode modules.

   New in version 3.3.

importlib.machinery.OPTIMIZED_BYTECODE_SUFFIXES

   A list of strings representing the file suffixes for optimized
   bytecode modules.

   New in version 3.3.

importlib.machinery.BYTECODE_SUFFIXES

   A list of strings representing the recognized file suffixes for
   bytecode modules. Set to either "DEBUG_BYTECODE_SUFFIXES" or
   "OPTIMIZED_BYTECODE_SUFFIXES" based on whether "__debug__" is true.

   New in version 3.3.

importlib.machinery.EXTENSION_SUFFIXES

   A list of strings representing the recognized file suffixes for
   extension modules.

   New in version 3.3.

importlib.machinery.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, "inspect.getmodulename()").

   New in version 3.3.

class importlib.machinery.BuiltinImporter

   An *importer* for built-in modules. All known built-in modules are
   listed in "sys.builtin_module_names". This class implements the
   "importlib.abc.MetaPathFinder" and "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 "Loader.exec_module()".

class importlib.machinery.FrozenImporter

   An *importer* for frozen modules. This class implements the
   "importlib.abc.MetaPathFinder" and "importlib.abc.InspectLoader"
   ABCs.

   Only class methods are defined by this class to alleviate the need
   for instantiation.

class importlib.machinery.WindowsRegistryFinder

   *Finder* for modules declared in the Windows registry.  This class
   implements the "importlib.abc.Finder" ABC.

   Only class methods are defined by this class to alleviate the need
   for instantiation.

   New in version 3.3.

class importlib.machinery.PathFinder

   A *Finder* for "sys.path" and package "__path__" attributes. This
   class implements the "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 *spec* for the module
      specified by *fullname* on "sys.path" or, if defined, on *path*.
      For each path entry that is searched, "sys.path_importer_cache"
      is checked. If a non-false object is found then it is used as
      the *path entry finder* to look for the module being searched
      for. If no entry is found in "sys.path_importer_cache", then
      "sys.path_hooks" is searched for a finder for the path entry
      and, if found, is stored in "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.

      New in version 3.4.

   classmethod find_module(fullname, path=None)

      A legacy wrapper around "find_spec()".

      Deprecated since version 3.4: Use "find_spec()" instead.

   classmethod invalidate_caches()

      Calls "importlib.abc.PathEntryFinder.invalidate_caches()" on all
      finders stored in "sys.path_importer_cache".

   Changed in version 3.4: Calls objects in "sys.path_hooks" with the
   current working directory for "''" (i.e. the empty string).

class importlib.machinery.FileFinder(path, *loader_details)

   A concrete implementation of "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 "importlib.invalidate_caches()".

   New in version 3.3.

   path

      The path the finder will search in.

   find_spec(fullname, target=None)

      Attempt to find the spec to handle *fullname* within "path".

      New in version 3.4.

   find_loader(fullname)

      Attempt to find the loader to handle *fullname* within "path".

   invalidate_caches()

      Clear out the internal cache.

   classmethod path_hook(*loader_details)

      A class method which returns a closure for use on
      "sys.path_hooks". An instance of "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,
      "ImportError" is raised.

class importlib.machinery.SourceFileLoader(fullname, path)

   A concrete implementation of "importlib.abc.SourceLoader" by
   subclassing "importlib.abc.FileLoader" and providing some concrete
   implementations of other methods.

   New in version 3.3.

   name

      The name of the module that this loader will handle.

   path

      The path to the source file.

   is_package(fullname)

      Return true if "path" appears to be for a package.

   path_stats(path)

      Concrete implementation of
      "importlib.abc.SourceLoader.path_stats()".

   set_data(path, data)

      Concrete implementation of
      "importlib.abc.SourceLoader.set_data()".

   load_module(name=None)

      Concrete implementation of "importlib.abc.Loader.load_module()"
      where specifying the name of the module to load is optional.

class importlib.machinery.SourcelessFileLoader(fullname, path)

   A concrete implementation of "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.

   New in version 3.3.

   name

      The name of the module the loader will handle.

   path

      The path to the bytecode file.

   is_package(fullname)

      Determines if the module is a package based on "path".

   get_code(fullname)

      Returns the code object for "name" created from "path".

   get_source(fullname)

      Returns "None" as bytecode files have no source when this loader
      is used.

   load_module(name=None)

   Concrete implementation of "importlib.abc.Loader.load_module()"
   where specifying the name of the module to load is optional.

class importlib.machinery.ExtensionFileLoader(fullname, path)

   A concrete implementation of "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.

   New in version 3.3.

   name

      Name of the module the loader supports.

   path

      Path to the extension module.

   load_module(name=None)

      Loads the extension module if and only if *fullname* is the same
      as "name" or is "None".

      Note: Due to limitations in the extension module C-API, for
        now ExtensionFileLoader does not implement
        "Loader.exec_module()".

   is_package(fullname)

      Returns "True" if the file path points to a package’s "__init__"
      module based on "EXTENSION_SUFFIXES".

   get_code(fullname)

      Returns "None" as extension modules lack a code object.

   get_source(fullname)

      Returns "None" as extension modules do not have source code.

   get_filename(fullname)

      Returns "path".

      New in version 3.4.

class importlib.machinery.ModuleSpec(name, loader, *, origin=None, loader_state=None, is_package=None)

   A specification for a module’s import-system-related state.

   New in version 3.4.

   name

   ("__name__")

   A string for the fully-qualified name of the module.

   loader

   ("__loader__")

   The loader to use for loading.  For namespace packages this should
   be set to None.

   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.

   submodule_search_locations

   ("__path__")

   List of strings for where to find submodules, if a package (None
   otherwise).

   loader_state

   Container of extra module-specific data for use during loading (or
   None).

   cached

   ("__cached__")

   String for where the compiled module should be stored (or None).

   parent

   ("__package__")

   (Read-only) Fully-qualified name of the package to which the module
   belongs as a submodule (or None).

   has_location

   Boolean indicating whether or not the module’s “origin” attribute
   refers to a loadable location.


31.5.5. "importlib.util" – Utility code for importers
=====================================================

This module contains the various objects that help in the construction
of an *importer*.

importlib.util.MAGIC_NUMBER

   The bytes which represent the bytecode version number. If you need
   help with loading/writing bytecode then consider
   "importlib.abc.SourceLoader".

   New in version 3.4.

importlib.util.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
   "get_tag()"; if "sys.implementation.cache_tag" is not defined then
   "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.

   New in version 3.4.

importlib.util.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
   "sys.implementation.cache_tag" is not defined,
   "NotImplementedError" is raised.

   New in version 3.4.

importlib.util.decode_source(source_bytes)

   Decode the given bytes representing source code and return it as a
   string with universal newlines (as required by
   "importlib.abc.InspectLoader.get_source()").

   New in version 3.4.

importlib.util.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.

   "ValueError" is raised if **name** is a relative module name but
   package is a false value (e.g. "None" or the empty string).
   "ValueError" is also raised a relative name would escape its
   containing package (e.g. requesting "..bacon" from within the
   "spam" package).

   New in version 3.3.

importlib.util.find_spec(name, package=None)

   Find the *spec* for a module, optionally relative to the specified
   **package** name. If the module is in "sys.modules", then
   "sys.modules[name].__spec__" is returned (unless the spec would be
   "None" or is not set, in which case "ValueError" is raised).
   Otherwise a search using "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 "import_module()".

   New in version 3.4.

@importlib.util.module_for_loader

   A *decorator* for "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 *loader*. If the module is not found in
   "sys.modules" then a new one is constructed. Regardless of where
   the module came from, "__loader__" set to **self** and
   "__package__" is set based on what
   "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 "sys.modules", then the module will be removed to prevent
   a partially initialized module from being in left in "sys.modules".
   If the module was already in "sys.modules" then it is left alone.

   Changed in version 3.3: "__loader__" and "__package__" are
   automatically set (when possible).

   Changed in version 3.4: Set "__name__", "__loader__" "__package__"
   unconditionally to support reloading.

   Deprecated since version 3.4: The import machinery now directly
   performs all the functionality provided by this function.

@importlib.util.set_loader

   A *decorator* for "importlib.abc.Loader.load_module()" to set the
   "__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 "__loader__" should be set to.

   Changed in version 3.4: Set "__loader__" if set to "None", as if
   the attribute does not exist.

   Deprecated since version 3.4: The import machinery takes care of
   this automatically.

@importlib.util.set_package

   A *decorator* for "importlib.abc.Loader.load_module()" to set the
   "__package__" attribute on the returned module. If "__package__" is
   set and has a value other than "None" it will not be changed.

   Deprecated since version 3.4: The import machinery takes care of
   this automatically.

importlib.util.spec_from_loader(name, loader, *, origin=None, is_package=None)

   A factory function for creating a "ModuleSpec" instance based on a
   loader.  The parameters have the same meaning as they do for
   ModuleSpec.  The function uses available *loader* APIs, such as
   "InspectLoader.is_package()", to fill in any missing information on
   the spec.

   New in version 3.4.

importlib.util.spec_from_file_location(name, location, *, loader=None, submodule_search_locations=None)

   A factory function for creating a "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.

   New in version 3.4.
