pkgutil
— 包扩展实用程序
¶
源代码： Lib/pkgutil.py
This module provides utilities for the import system, in particular package support.
A namedtuple that holds a brief summary of a module’s info.
Added in version 3.6.
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__)
For each directory on
sys.path
that has a subdirectory that matches the package name, add the subdirectory to the package’s
__path__
. 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 the
site
module for more information), except that it doesn’t special-case lines starting with
import
。
*.pkg
file is trusted at face value: apart from skipping blank lines and ignoring comments, 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 of
sys.path
that are not strings referring to existing directories are ignored. Unicode items on
sys.path
that cause errors when used as filenames may cause this function to raise an exception (in line with
os.path.isdir()
behavior).
Retrieve a module loader 为给定 fullname .
This is a backwards compatibility wrapper around
importlib.util.find_spec()
that converts most failures to
ImportError
and only returns the loader rather than the full
importlib.machinery.ModuleSpec
.
3.3 版改变：
Updated to be based directly on
importlib
rather than relying on the package internal
PEP 302
import emulation.
3.4 版改变： Updated to be based on PEP 451
Deprecated since version 3.12, will be removed in version 3.14:
使用
importlib.util.find_spec()
代替。
Retrieve a finder 为给定 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.
3.3 版改变：
Updated to be based directly on
importlib
rather than relying on the package internal
PEP 302
import emulation.
Get a loader 对象为 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__
.
3.3 版改变：
Updated to be based directly on
importlib
rather than relying on the package internal
PEP 302
import emulation.
3.4 版改变： Updated to be based on PEP 451
Deprecated since version 3.12, will be removed in version 3.14:
使用
importlib.util.find_spec()
代替。
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.
3.3 版改变：
Updated to be based directly on
importlib
rather than relying on the package internal
PEP 302
import emulation.
Yields
ModuleInfo
for all submodules on
path
, or, if
path
is
None
, all top-level modules on
sys.path
.
path
应该为
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.
注意
Only works for a
finder
which defines an
iter_modules()
method. This interface is non-standard, so the module also provides implementations for
importlib.machinery.FileFinder
and
zipimport.zipimporter
.
3.3 版改变：
Updated to be based directly on
importlib
rather than relying on the package internal
PEP 302
import emulation.
Yields
ModuleInfo
for all modules recursively on
path
, or, if
path
is
None
, all accessible modules.
path
应该为
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.
范例：
# list all modules python can access walk_packages() # list all submodules of ctypes walk_packages(ctypes.__path__, ctypes.__name__ + '.')
注意
Only works for a
finder
which defines an
iter_modules()
method. This interface is non-standard, so the module also provides implementations for
importlib.machinery.FileFinder
and
zipimport.zipimporter
.
3.3 版改变：
Updated to be based directly on
importlib
rather than relying on the package internal
PEP 302
import emulation.
Get a resource from a package.
This is a wrapper for the
loader
get_data
API。
包
argument should be the name of a package, in standard module format (
foo.bar
)。
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
，那么
None
is returned. In particular, the
loader
for
名称空间包
不支持
get_data
.
Resolve a name to an object.
This functionality is used in numerous places in the standard library (see bpo-12915 ) - and equivalent functionality is also in widely used third-party packages such as setuptools, Django and Pyramid.
It is expected that name will be a string in one of the following formats, where W is shorthand for a valid Python identifier and dot stands for a literal period in these pseudo-regexes:
W(.W)*
W(.W)*:(W(.W)*)?
The first form is intended for backward compatibility only. It assumes that some part of the dotted name is a package, and the rest is an object somewhere within that package, possibly nested inside other objects. Because the place where the package stops and the object hierarchy starts can’t be inferred by inspection, repeated attempts to import must be done with this form.
In the second form, the caller makes the division point clear through the provision of a single colon: the dotted name to the left of the colon is a package to be imported, and the dotted name to the right is the object hierarchy within that package. Only one import is needed in this form. If it ends with the colon, then a module object is returned.
The function will return an object (which might be a module), or raise one of the following exceptions:
ValueError
– if
name
isn’t in a recognised format.
ImportError
– if an import failed when it shouldn’t have.
AttributeError
– If a failure occurred when traversing the object hierarchy within the imported package to get to the desired object.
Added in version 3.9.