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Thorough review of importlib docs. Reviewed by Brett himself.

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Guido van Rossum 2009-03-30 20:34:57 +00:00
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Doc/library/importlib.rst
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@ -37,7 +37,7 @@ Details on providing custom importers can be found in :pep:`302`.
The :func:`.__import__` function
The built-in function for which the :keyword:`import` statement is
syntactic sugar for.
syntactic sugar.
:pep:`235`
Import on Case-Insensitive Platforms
@ -71,8 +71,8 @@ Functions
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 package which is to act as the anchor for resolving the
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``).
@ -80,7 +80,11 @@ Functions
:func:`__import__`. This means all semantics of the function are derived
from :func:`__import__`, including requiring the package from which an
import is occurring to have been previously imported (i.e., *package*
must already be imported).
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``).
:mod:`importlib.abc` -- Abstract base classes related to import
---------------------------------------------------------------
@ -96,21 +100,21 @@ are also provided to help in implementing the core ABCs.
.. class:: Finder
An abstract base class representing a :term:`finder`.
See :pep:`302` for the exact definition for a finder.
.. method:: find_module(fullname, path=None)
An abstract method for finding a :term:`loader` for the specified
module. If the :term:`finder` is found on :data:`sys.meta_path` and the
module to be searched for is a subpackage or module then *path* is set
to the value of :attr:`__path__` from the parent package. If a loader
module to be searched for is a subpackage or module then *path* will
be the value of :attr:`__path__` from the parent package. If a loader
cannot be found, :keyword:`None` is returned.
The exact definition of a :term:`finder` can be found in :pep:`302`.
.. class:: Loader
An abstract base class for a :term:`loader`.
See :pep:`302` for the exact definition for a loader.
.. method:: load_module(fullname)
@ -118,18 +122,19 @@ are also provided to help in implementing the core ABCs.
loaded, :exc:`ImportError` is raised, otherwise the loaded module is
returned.
If the requested module is already exists in :data:`sys.modules`, that
If the requested module already exists in :data:`sys.modules`, that
module should be used and reloaded.
Otherwise a new module is to be created by the loader and inserted into
:data:`sys.modules` before any loading begins to prevent recursion from
the import. If the loader inserted into a module and the load fails it
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 is expected to set several attributes on the module when
adding a new module to :data:`sys.modules`.
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.
@ -139,7 +144,7 @@ are also provided to help in implementing the core ABCs.
modules).
- :attr:`__path__`
Set to a list of strings specifying the search path within a
A list of strings specifying the search path within a
package. This attribute is not set on modules.
- :attr:`__package__`
@ -149,9 +154,9 @@ are also provided to help in implementing the core ABCs.
for :attr:`__package__`.
- :attr:`__loader__`
Set to the loader used to load the module.
See :pep:`302` for the exact definition for a loader.
The loader used to load the module.
(This is not set by the built-in import machinery,
but it should be set whenever a :term:`loader` is used.)
.. class:: ResourceLoader
@ -163,17 +168,20 @@ are also provided to help in implementing the core ABCs.
.. 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 can implement this
abstract method to give direct access
Loaders that have a file-like storage back-end
that allows storing arbitrary data (e.g. a zip archive loader)
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:`__path__` attribute or an item from :attr:`__path__`.
.. XXX What's the difference between the latter two? (Maybe one is __file__?)
.. XXX Could use a clarification so as not to depend on PEP 302.
.. class:: InspectLoader
An abstract base class for a :term:`loader` which implements the optional
:pep:`302` protocol for loaders which inspect modules.
:pep:`302` protocol for loaders that inspect modules.
.. method:: get_code(fullname)
@ -185,7 +193,7 @@ are also provided to help in implementing the core ABCs.
.. method:: get_source(fullname)
An abstract method to return the source of a module. It is returned as
a string with universal newline support. Returns :keyword:`None` if no
a text string with universal newlines. Returns :keyword:`None` if no
source is available (e.g. a built-in module). Raises :exc:`ImportError`
if the loader cannot find the module specified.
@ -224,14 +232,17 @@ are also provided to help in implementing the core ABCs.
A concrete implementation of
:meth:`importlib.abc.InspectLoader.get_code` that creates code objects
from Python source code.
from Python source code, by requesting the source code (using
:meth:`source_path` and :meth:`get_data`), converting it to standard
newlines, and compiling it with the built-in :func:`compile` function.
.. method:: get_source(fullname)
A concrete implementation of
:meth:`importlib.abc.InspectLoader.get_source`. Uses
:meth:`importlib.abc.InspectLoader.get_data` and :meth:`source_path` to
get the source code.
get the source code. It tries to guess the source encoding using
:func:`tokenize.detect_encoding`.
.. class:: PyPycLoader
@ -250,8 +261,9 @@ are also provided to help in implementing the core ABCs.
.. method:: bytecode_path(fullname)
An abstract method which returns the path to the bytecode for the
specified module. :keyword:`None` is returned if there is no bytecode.
:exc:`ImportError` is raised if the module is not found.
specified module, if it exists. It returns :keyword:`None`
if no bytecode exists (yet).
Raises :exc:`ImportError` if the module is not found.
.. method:: write_bytecode(fullname, bytecode)
@ -259,6 +271,7 @@ are also provided to help in implementing the core ABCs.
use. If the bytecode is written, return :keyword:`True`. Return
:keyword:`False` if the bytecode could not be written. This method
should not be called if :data:`sys.dont_write_bytecode` is true.
The *bytecode* argument should be a bytes string or bytes array.
:mod:`importlib.machinery` -- Importers and path hooks
@ -328,16 +341,18 @@ an :term:`importer`.
.. function:: module_for_loader(method)
A :term:`decorator` for a :term:`loader` which handles selecting the proper
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 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
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. Otherwise the module found in
:data:`sys.modules` will be passed into the method. If an
@ -346,18 +361,17 @@ an :term:`importer`.
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 what module object a
Use of this decorator handles all the details of which module object a
loader should initialize as specified by :pep:`302`.
.. function:: set_loader(fxn)
A :term:`decorator` for a :term:`loader` to set the :attr:`__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 is what :attr:`__loader__` should be set to.
.. function:: set_package(fxn)
A :term:`decorator` for a :term:`loader` to set the :attr:`__package__`
@ -365,3 +379,5 @@ an :term:`importer`.
set and has a value other than :keyword:`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`.
.. XXX This whole chapter desperately needs examples...