You can also get a collection of entry points selectable by properties of the EntryPoint (typically ‘group’ or ‘name’), such as
console_scripts
,
distutils.commands
and others. Each group contains a collection of
EntryPoint
对象。
You can get the
metadata for a distribution
:
>>> list(metadata('wheel'))
['Metadata-Version', 'Name', 'Version', 'Summary', 'Home-page', 'Author', 'Author-email', 'Maintainer', 'Maintainer-email', 'License', 'Project-URL', 'Project-URL', 'Project-URL', 'Keywords', 'Platform', 'Classifier', 'Classifier', 'Classifier', 'Classifier', 'Classifier', 'Classifier', 'Classifier', 'Classifier', 'Classifier', 'Classifier', 'Classifier', 'Classifier', 'Requires-Python', 'Provides-Extra', 'Requires-Dist', 'Requires-Dist']
You can also get a
distribution’s version number
, list its
constituent files
, and get a list of the distribution’s
分发要求
.
-
exception
importlib.metadata.
PackageNotFoundError
¶
-
子类化的
ModuleNotFoundError
raised by several functions in this module when queried for a distribution package which is not installed in the current Python environment.
函数式 API
¶
This package provides the following functionality via its public API.
入口点
¶
-
importlib.metadata.
entry_points
(
**
select_params
)
¶
-
返回
EntryPoints
instance describing entry points for the current environment. Any given keyword parameters are passed to the
select()
method for comparison to the attributes of the individual entry point definitions.
Note: it is not currently possible to query for entry points based on their
EntryPoint.dist
attribute (as different
Distribution
instances do not currently compare equal, even if they have the same attributes)
-
class
importlib.metadata.
EntryPoints
¶
-
Details of a collection of installed entry points.
Also provides a
.groups
attribute that reports all identified entry point groups, and a
.names
attribute that reports all identified entry point names.
-
class
importlib.metadata.
EntryPoint
¶
-
Details of an installed entry point.
每个
EntryPoint
instance has
.name
,
.group
，和
.value
attributes and a
.load()
method to resolve the value. There are also
.module
,
.attr
，和
.extras
attributes for getting the components of the
.value
attribute, and
.dist
for obtaining information regarding the distribution package that provides the entry point.
Query all entry points:
>>> eps = entry_points()
The
entry_points()
函数返回
EntryPoints
object, a collection of all
EntryPoint
objects with
names
and
groups
attributes for convenience:
>>> sorted(eps.groups)
['console_scripts', 'distutils.commands', 'distutils.setup_keywords', 'egg_info.writers', 'setuptools.installation']
EntryPoints
拥有
select()
method to select entry points matching specific properties. Select entry points in the
console_scripts
group:
>>> scripts = eps.select(group='console_scripts')
Equivalently, since
entry_points()
passes keyword arguments through to select:
>>> scripts = entry_points(group='console_scripts')
Pick out a specific script named “wheel” (found in the wheel project):
>>> 'wheel' in scripts.names
True
>>> wheel = scripts['wheel']
Equivalently, query for that entry point during selection:
>>> (wheel,) = entry_points(group='console_scripts', name='wheel')
>>> (wheel,) = entry_points().select(group='console_scripts', name='wheel')
Inspect the resolved entry point:
>>> wheel
EntryPoint(name='wheel', value='wheel.cli:main', group='console_scripts')
>>> wheel.module
'wheel.cli'
>>> wheel.attr
'main'
>>> wheel.extras
[]
>>> main = wheel.load()
>>> main
<function main at 0x103528488>
The
group
and
name
are arbitrary values defined by the package author and usually a client will wish to resolve all entry points for a particular group. Read
the setuptools docs
for more information on entry points, their definition, and usage.
3.12 版改变：
The “selectable” entry points were introduced in
importlib_metadata
3.6 and Python 3.10. Prior to those changes,
entry_points
accepted no parameters and always returned a dictionary of entry points, keyed by group. With
importlib_metadata
5.0 and Python 3.12,
entry_points
always returns an
EntryPoints
对象。见
backports.entry_points_selectable
for compatibility options.
Changed in version 3.13:
EntryPoint
objects no longer present a tuple-like interface (
__getitem__()
).
分发版本
¶
-
importlib.metadata.
version
(
distribution_name
)
¶
-
Return the installed distribution package version for the named distribution package.
引发
PackageNotFoundError
if the named distribution package is not installed in the current Python environment.
The
version()
function is the quickest way to get a
Distribution Package
’s version number, as a string:
>>> version('wheel')
'0.32.3'
分发文件
¶
-
importlib.metadata.
文件
(
distribution_name
)
¶
-
Return the full set of files contained within the named distribution package.
引发
PackageNotFoundError
if the named distribution package is not installed in the current Python environment.
返回
None
if the distribution is found but the installation database records reporting the files associated with the distribuion package are missing.
-
class
importlib.metadata.
PackagePath
¶
-
A
pathlib.PurePath
derived object with additional
dist
,
size
，和
hash
properties corresponding to the distribution package’s installation metadata for that file.
The
files()
function takes a
Distribution Package
name and returns all of the files installed by this distribution. Each file is reported as a
PackagePath
instance. For example:
>>> util = [p for p in files('wheel') if 'util.py' in str(p)][0]
>>> util
PackagePath('wheel/util.py')
>>> util.size
859
>>> util.dist
<importlib.metadata._hooks.PathDistribution object at 0x101e0cef0>
>>> util.hash
<FileHash mode: sha256 value: bYkw5oMccfazVCoYQwKkkemoVyMAFoR34mmKBx8R1NI>
Once you have the file, you can also read its contents:
>>> print(util.read_text())
import base64
import sys
...
def as_bytes(s):
if isinstance(s, text_type):
return s.encode('utf-8')
return s
还可以使用
locate()
method to get the absolute path to the file:
>>> util.locate()
PosixPath('/home/gustav/example/lib/site-packages/wheel/util.py')
In the case where the metadata file listing files (
RECORD
or
SOURCES.txt
) is missing,
files()
将返回
None
. The caller may wish to wrap calls to
files()
in
always_iterable
or otherwise guard against this condition if the target distribution is not known to have the metadata present.
分发要求
¶
-
importlib.metadata.
requires
(
distribution_name
)
¶
-
Return the declared dependency specifiers for the named distribution package.
引发
PackageNotFoundError
if the named distribution package is not installed in the current Python environment.
To get the full set of requirements for a
Distribution Package
，使用
requires()
函数：
>>> requires('wheel')
["pytest (>=3.0.0) ; extra == 'test'", "pytest-cov ; extra == 'test'"]
Mapping import to distribution packages
¶
-
importlib.metadata.
packages_distributions
(
)
¶
-
Return a mapping from the top level module and import package names found via
sys.meta_path
to the names of the distribution packages (if any) that provide the corresponding files.
To allow for namespace packages (which may have members provided by multiple distribution packages), each top level import name maps to a list of distribution names rather than mapping directly to a single name.
A convenience method to resolve the
Distribution Package
name (or names, in the case of a namespace package) that provide each importable top-level Python module or
Import Package
:
>>> packages_distributions()
{'importlib_metadata': ['importlib-metadata'], 'yaml': ['PyYAML'], 'jaraco': ['jaraco.classes', 'jaraco.functools'], ...}
Some editable installs,
do not supply top-level names
, and thus this function is not reliable with such installs.
3.10 版添加。
分布
¶
-
importlib.metadata.
distribution
(
distribution_name
)
¶
-
返回
Distribution
instance describing the named distribution package.
引发
PackageNotFoundError
if the named distribution package is not installed in the current Python environment.
-
class
importlib.metadata.
分发
¶
-
Details of an installed distribution package.
Note: different
Distribution
instances do not currently compare equal, even if they relate to the same installed distribution and accordingly have the same attributes.
While the module level API described above is the most common and convenient usage, you can get all of that information from the
Distribution
类。
Distribution
is an abstract object that represents the metadata for a Python
Distribution Package
. You can get the concreate
Distribution
subclass instance for an installed distribution package by calling the
distribution()
函数：
>>> from importlib.metadata import distribution
>>> dist = distribution('wheel')
>>> type(dist)
<class 'importlib.metadata.PathDistribution'>
Thus, an alternative way to get the version number is through the
Distribution
实例：
>>> dist.version
'0.32.3'
There are all kinds of additional metadata available on
Distribution
实例：
>>> dist.metadata['Requires-Python']
'>=2.7, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*'
>>> dist.metadata['License']
'MIT'
For editable packages, an
origin
property may present
PEP 610
metadata:
>>> dist.origin.url
'file:///path/to/wheel-0.32.3.editable-py3-none-any.whl'
The full set of available metadata is not described here. See the PyPA
Core metadata specification
了解额外细节。
Added in version 3.13:
The
.origin
property was added.
Distribution Discovery
¶
By default, this package provides built-in support for discovery of metadata for file system and zip file
Distribution Package
s. This metadata finder search defaults to
sys.path
, but varies slightly in how it interprets those values from how other import machinery does. In particular:
扩展搜索算法
¶
因为
Distribution Package
metadata is not available through
sys.path
searches, or package loaders directly, the metadata for a distribution is found through import system
finders
. To find a distribution package’s metadata,
importlib.metadata
queries the list of
元路径查找器
on
sys.meta_path
.
默认情况下
importlib.metadata
installs a finder for distribution packages found on the file system. This finder doesn’t actually find any
distributions
, but it can find their metadata.
The abstract class
importlib.abc.MetaPathFinder
defines the interface expected of finders by Python’s import system.
importlib.metadata
extends this protocol by looking for an optional
find_distributions
callable on the finders from
sys.meta_path
and presents this extended interface as the
DistributionFinder
abstract base class, which defines this abstract method:
@abc.abstractmethod
def find_distributions(context=DistributionFinder.Context()):
"""Return an iterable of all Distribution instances capable of
loading the metadata for packages for the indicated ``context``.
"""
The
DistributionFinder.Context
object provides
.path
and
.name
properties indicating the path to search and name to match and may supply other relevant context.
What this means in practice is that to support finding distribution package metadata in locations other than the file system, subclass
Distribution
and implement the abstract methods. Then from a custom finder, return instances of this derived
Distribution
在
find_distributions()
方法。
范例
¶
Consider for example a custom finder that loads Python modules from a database:
class DatabaseImporter(importlib.abc.MetaPathFinder):
def __init__(self, db):
self.db = db
def find_spec(self, fullname, target=None) -> ModuleSpec:
return self.db.spec_from_name(fullname)
sys.meta_path.append(DatabaseImporter(connect_db(...)))
That importer now presumably provides importable modules from a database, but it provides no metadata or entry points. For this custom importer to provide metadata, it would also need to implement
DistributionFinder
:
from importlib.metadata import DistributionFinder
class DatabaseImporter(DistributionFinder):
...
def find_distributions(self, context=DistributionFinder.Context()):
query = dict(name=context.name) if context.name else {}
for dist_record in self.db.query_distributions(query):
yield DatabaseDistribution(dist_record)
In this way,
query_distributions
would return records for each distribution served by the database matching the query. For example, if
requests-1.0
is in the database,
find_distributions
would yield a
DatabaseDistribution
for
Context(name='requests')
or
Context(name=None)
.
For the sake of simplicity, this example ignores
context.path
。
path
attribute defaults to
sys.path
and is the set of import paths to be considered in the search. A
DatabaseImporter
could potentially function without any concern for a search path. Assuming the importer does no partitioning, the “path” would be irrelevant. In order to illustrate the purpose of
path
, the example would need to illustrate a more complex
DatabaseImporter
whose behavior varied depending on
sys.path
/
PYTHONPATH
. In that case, the
find_distributions
should honor the
context.path
and only yield
Distribution
s pertinent to that path.
DatabaseDistribution
, then, would look something like:
class DatabaseDistribution(importlib.metadata.Distribution):
def __init__(self, record):
self.record = record
def read_text(self, filename):
"""
Read a file like "METADATA" for the current distribution.
"""
if filename == "METADATA":
return f"""Name: {self.record.name}
Version: {self.record.version}
"""
if filename == "entry_points.txt":
return "\n".join(
f"""[{ep.group}]\n{ep.name}={ep.value}"""
for ep in self.record.entry_points)
def locate_file(self, path):
raise RuntimeError("This distribution has no file system")
This basic implementation should provide metadata and entry points for packages served by the
DatabaseImporter
, assuming that the
record
supplies suitable
.name
,
.version
，和
.entry_points
属性。
The
DatabaseDistribution
may also provide other metadata files, like
RECORD
(required for
Distribution.files
) or override the implementation of
Distribution.files
. See the source for more inspiration.
