pkgutil
— 包扩展实用程序
¶
2.3 版新增。
源代码： Lib/pkgutil.py
This module provides utilities for the import system, in particular package support.
pkgutil.
extend_path
(
path
,
名称
)
¶
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 on
sys.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 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 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 of
sys.path
that are not (Unicode or 8-bit) 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).
pkgutil.
ImpImporter
(
dirname=None
)
¶
PEP 302 Importer that wraps Python’s “classic” import algorithm.
若
dirname
is a string, a
PEP 302
importer is created that searches that directory. If
dirname
is
None
，
PEP 302
importer is created that searches the current
sys.path
, plus any modules that are frozen or built-in.
注意，
ImpImporter
does not currently support being used by placement on
sys.meta_path
.
pkgutil.
ImpLoader
(
fullname
,
file
,
filename
,
etc
)
¶
PEP 302 Loader that wraps Python’s “classic” import algorithm.
pkgutil.
find_loader
(
fullname
)
¶
Find a PEP 302 “loader” object for fullname .
若
fullname
contains dots, path must be the containing package’s
__path__
。返回
None
if the module cannot be found or imported. This function uses
iter_importers()
, and is thus subject to the same limitations regarding platform-specific special import locations such as the Windows registry.
pkgutil.
get_importer
(
path_item
)
¶
Retrieve a PEP 302 importer for the given path_item .
The returned importer is cached in
sys.path_importer_cache
if it was newly created by a path hook.
If there is no importer, a wrapper around the basic import machinery is returned. This wrapper is never inserted into the importer cache (
None
is inserted instead).
The cache (or part of it) can be cleared manually if a rescan of
sys.path_hooks
is necessary.
pkgutil.
get_loader
(
module_or_name
)
¶
Get a PEP 302 “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__
.
此函数使用
iter_importers()
, and is thus subject to the same limitations regarding platform-specific special import locations such as the Windows registry.
pkgutil.
iter_importers
(
fullname=''
)
¶
Yield PEP 302 importers for the given module name.
If fullname contains a ‘.’, the importers will be for the package containing fullname, otherwise they will be importers for
sys.meta_path
,
sys.path
, and Python’s “classic” import machinery, in that order. If the named module is in a package, that package is imported as a side effect of invoking this function.
Non-
PEP 302
mechanisms (e.g. the Windows registry) used by the standard import machinery to find files in alternative locations are partially supported, but are searched
after
sys.path
. Normally, these locations are searched
before
sys.path
, preventing
sys.path
entries from shadowing them.
For this to cause a visible difference in behaviour, there must be a module or package name that is accessible via both
sys.path
and one of the non-
PEP 302
file system mechanisms. In this case, the emulation will find the former version, while the builtin import mechanism will find the latter.
Items of the following types can be affected by this discrepancy:
imp.C_EXTENSION
,
imp.PY_SOURCE
,
imp.PY_COMPILED
,
imp.PKG_DIRECTORY
.
pkgutil.
iter_modules
(
path=None
,
prefix=''
)
¶
Yields
(module_loader, name, ispkg)
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.
pkgutil.
walk_packages
(
path=None
,
prefix=''
,
onerror=None
)
¶
Yields
(module_loader, name, ispkg)
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__ + '.')
pkgutil.
get_data
(
包
,
resource
)
¶
Get a resource from a package.
This is a wrapper for the
PEP 302
loader
get_data()
API。
package
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
PEP 302
loader which does not support
get_data()
，那么
None
被返回。
2.6 版新增。