31.2. pkgutil
— Package extension utility¶
Source code: Lib/pkgutil.py
This module provides utilities for the import system, in particular package support.
-
pkgutil.
extend_path
(path, name)¶ Extend the search path for the modules which comprise a package. Intended use is to place the following code in a package’s
__init__.py
:from pkgutil import extend_path __path__ = extend_path(__path__, __name__)
This will add to the package’s
__path__
all subdirectories of directories onsys.path
named after the package. This is useful if one wants to distribute different parts of a single logical package as multiple directories.It also looks for
*.pkg
files beginning where*
matches the name argument. This feature is similar to*.pth
files (see thesite
module for more information), except that it doesn’t special-case lines starting withimport
. A*.pkg
file is trusted at face value: apart from checking for duplicates, all entries found in a*.pkg
file are added to the path, regardless of whether they exist on the filesystem. (This is a feature.)If the input path is not a list (as is the case for frozen packages) it is returned unchanged. The input path is not modified; an extended copy is returned. Items are only appended to the copy at the end.
It is assumed that
sys.path
is a sequence. Items ofsys.path
that are not strings referring to existing directories are ignored. Unicode items onsys.path
that cause errors when used as filenames may cause this function to raise an exception (in line withos.path.isdir()
behavior).
-
class
pkgutil.
ImpImporter
(dirname=None)¶ PEP 302 Finder that wraps Python’s «classic» import algorithm.
If dirname is a string, a PEP 302 finder is created that searches that directory. If dirname is
None
, a PEP 302 finder is created that searches the currentsys.path
, plus any modules that are frozen or built-in.Note that
ImpImporter
does not currently support being used by placement onsys.meta_path
.Obsoleto desde la versión 3.3: This emulation is no longer needed, as the standard import mechanism is now fully PEP 302 compliant and available in
importlib
.
-
class
pkgutil.
ImpLoader
(fullname, file, filename, etc)¶ Loader that wraps Python’s «classic» import algorithm.
Obsoleto desde la versión 3.3: This emulation is no longer needed, as the standard import mechanism is now fully PEP 302 compliant and available in
importlib
.
-
pkgutil.
find_loader
(fullname)¶ Retrieve a module loader for the given fullname.
This is a backwards compatibility wrapper around
importlib.util.find_spec()
that converts most failures toImportError
and only returns the loader rather than the fullModuleSpec
.Distinto en la versión 3.3: Updated to be based directly on
importlib
rather than relying on the package internal PEP 302 import emulation.Distinto en la versión 3.4: Updated to be based on PEP 451
-
pkgutil.
get_importer
(path_item)¶ Retrieve a finder for the given path_item.
The returned finder is cached in
sys.path_importer_cache
if it was newly created by a path hook.The cache (or part of it) can be cleared manually if a rescan of
sys.path_hooks
is necessary.Distinto en la versión 3.3: Updated to be based directly on
importlib
rather than relying on the package internal PEP 302 import emulation.
-
pkgutil.
get_loader
(module_or_name)¶ Get a loader object for module_or_name.
If the module or package is accessible via the normal import mechanism, a wrapper around the relevant part of that machinery is returned. Returns
None
if the module cannot be found or imported. If the named module is not already imported, its containing package (if any) is imported, in order to establish the package__path__
.Distinto en la versión 3.3: Updated to be based directly on
importlib
rather than relying on the package internal PEP 302 import emulation.Distinto en la versión 3.4: Updated to be based on PEP 451
-
pkgutil.
iter_importers
(fullname='')¶ Yield finder objects for the given module name.
If fullname contains a “.”, the finders will be for the package containing fullname, otherwise they will be all registered top level finders (i.e. those on both sys.meta_path and sys.path_hooks).
If the named module is in a package, that package is imported as a side effect of invoking this function.
If no module name is specified, all top level finders are produced.
Distinto en la versión 3.3: Updated to be based directly on
importlib
rather than relying on the package internal PEP 302 import emulation.
-
pkgutil.
iter_modules
(path=None, prefix='')¶ Yields
(module_finder, name, ispkg)
for all submodules on path, or, if path isNone
, all top-level modules onsys.path
.path should be either
None
or a list of paths to look for modules in.prefix is a string to output on the front of every module name on output.
Nota
Only works for a finder which defines an
iter_modules()
method. This interface is non-standard, so the module also provides implementations forimportlib.machinery.FileFinder
andzipimport.zipimporter
.Distinto en la versión 3.3: Updated to be based directly on
importlib
rather than relying on the package internal PEP 302 import emulation.
-
pkgutil.
walk_packages
(path=None, prefix='', onerror=None)¶ Yields
(module_finder, name, ispkg)
for all modules recursively on path, or, if path isNone
, all accessible modules.path should be either
None
or a list of paths to look for modules in.prefix is a string to output on the front of every module name on output.
Note that this function must import all packages (not all modules!) on the given path, in order to access the
__path__
attribute to find submodules.onerror is a function which gets called with one argument (the name of the package which was being imported) if any exception occurs while trying to import a package. If no onerror function is supplied,
ImportError
s are caught and ignored, while all other exceptions are propagated, terminating the search.Examples:
# list all modules python can access walk_packages() # list all submodules of ctypes walk_packages(ctypes.__path__, ctypes.__name__ + '.')
Nota
Only works for a finder which defines an
iter_modules()
method. This interface is non-standard, so the module also provides implementations forimportlib.machinery.FileFinder
andzipimport.zipimporter
.Distinto en la versión 3.3: Updated to be based directly on
importlib
rather than relying on the package internal PEP 302 import emulation.
-
pkgutil.
get_data
(package, resource)¶ Get a resource from a package.
This is a wrapper for the loader
get_data
API. The package argument should be the name of a package, in standard module format (foo.bar
). The resource argument should be in the form of a relative filename, using/
as the path separator. The parent directory name..
is not allowed, and nor is a rooted name (starting with a/
).The function returns a binary string that is the contents of the specified resource.
For packages located in the filesystem, which have already been imported, this is the rough equivalent of:
d = os.path.dirname(sys.modules[package].__file__) data = open(os.path.join(d, resource), 'rb').read()
If the package cannot be located or loaded, or it uses a loader which does not support
get_data
, thenNone
is returned. In particular, the loader for namespace packages does not supportget_data
.