importlib.metadata – 패키지 메타데이터 액세스

Added in version 3.8.

버전 3.10에서 변경: importlib.metadata는 더는 잠정적이지 않습니다.

Source code: Lib/importlib/metadata/__init__.py

importlib.metadata는 설치된 배포 패키지의 메타 데이터에 대한 액세스를 제공하는 라이브러리입니다. 에를 들어 진입 지점이나 최상위 이름(임포트 패키지, 모듈 등). 파이썬의 임포트 시스템에 내장된 이 라이브러리는 pkg_resources의 진입 지점 API와 메타데이터 API에서 유사한 기능을 대체하려고 합니다. importlib.resources와 함께, 이 패키지는 오래되고 덜 효율적인 pkg_resources 패키지를 사용할 필요를 제거합니다.

importlib.metadata operates on third-party distribution packages installed into Python’s site-packages directory via tools such as pip. Specifically, it works with distributions with discoverable dist-info or egg-info directories, and metadata defined by the Core metadata specifications.

중요

These are not necessarily equivalent to or correspond 1:1 with the top-level import package names that can be imported inside Python code. One distribution package can contain multiple import packages (and single modules), and one top-level import package may map to multiple distribution packages if it is a namespace package. You can use packages_distributions() to get a mapping between them.

By default, distribution metadata can live on the file system or in zip archives on sys.path. Through an extension mechanism, the metadata can live almost anywhere.

더 보기

https://importlib-metadata.readthedocs.io/

The documentation for importlib_metadata, which supplies a backport of importlib.metadata. This includes an API reference for this module’s classes and functions, as well as a migration guide for existing users of pkg_resources.

개요

pip를 사용하여 설치한 배포 패키지의 버전 문자열을 얻고 싶다고 가정해 봅시다. 우선 가상 환경을 만들고 그 안에 뭔가 설치합니다:

$ python -m venv example
$ source example/bin/activate
(example) $ python -m pip install wheel

다음을 실행하여 wheel에 대한 버전 문자열을 얻을 수 있습니다:

(example) $ python
>>> from importlib.metadata import version
>>> version('wheel')
'0.32.3'

console_scripts, distutils.commands나 그 외의 것들과 같은, EntryPoint 의 속성(보통 ‘group’ 이나 ‘name’)으로 선택할 수 있는 진입 지점의 컬렉션을 얻을 수도 있습니다. 각 그룹은 EntryPoint 객체의 컬랙션을 포함합니다.

여러분은 배포 메타데이터를 얻을 수 있습니다:

>>> 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']

또한 배포의 버전 번호를 가져오고, 구성 파일을 나열하고, 배포의 요구사항 리스트를 얻을 수 있습니다.

exception importlib.metadata.PackageNotFoundError

Subclass of ModuleNotFoundError raised by several functions in this module when queried for a distribution package which is not installed in the current Python environment.

기능적 API

이 패키지는 공용 API를 통해 다음과 같은 기능을 제공합니다.

진입 지점

importlib.metadata.entry_points(**select_params)

Returns a 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.

각 EntryPoint 인스턴스에는 .name, .group 및 .value 어트리뷰트가 있고 값을 결정하는 .load() 메서드가 있습니다. .value 어트리뷰트의 구성 요소를 가져오기 위한 .module, .attr 및 .extras 어트리뷰트도 있으며, .dist는 진입 지점을 제공하는 배포 패키지에 대한 정보를 얻는데 사용됩니다.

모든 진입 지점을 조회합니다:

>>> eps = entry_points()

The entry_points() function returns a 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 has a 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>

group과 name은 패키지 저자가 정의한 임의의 값이며 일반적으로 클라이언트는 특정 그룹에 대한 모든 진입 지점을 찾으려고 합니다. 진입 지점의 정의와 사용법에 대한 자세한 정보는 the setuptools docs를 읽으십시오.

버전 3.12에서 변경: 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 object. See backports.entry_points_selectable for compatibility options.

버전 3.13에서 변경: EntryPoint objects no longer present a tuple-like interface (__getitem__()).

배포 메타데이터

importlib.metadata.metadata(distribution_name)

Return the distribution metadata corresponding to the named distribution package as a PackageMetadata instance.

Raises PackageNotFoundError if the named distribution package is not installed in the current Python environment.

class importlib.metadata.PackageMetadata

A concrete implementation of the PackageMetadata protocol.

In addition to providing the defined protocol methods and attributes, subscripting the instance is equivalent to calling the get() method.

모든 배포 패키지는 metadata() 함수를 사용하여 추출할 수 있는 몇 가지 메타 데이터가 포함되어 있습니다:

>>> wheel_metadata = metadata('wheel')

반환된 데이터 구조의 키는 메타데이터 키워드의 이름을 지정하고, 값은 배포 메타데이터에서 구문 분석하지 않은 채로 반환됩니다:

>>> wheel_metadata['Requires-Python']
'>=2.7, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*'

PackageMetadata also presents a json attribute that returns all the metadata in a JSON-compatible form per PEP 566:

>>> wheel_metadata.json['requires_python']
'>=2.7, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*'

The full set of available metadata is not described here. See the PyPA Core metadata specification for additional details.

버전 3.10에서 변경: The Description is now included in the metadata when presented through the payload. Line continuation characters have been removed.

The json attribute was added.

배포 버전

importlib.metadata.version(distribution_name)

Return the installed distribution package version for the named distribution package.

Raises PackageNotFoundError if the named distribution package is not installed in the current Python environment.

version() 함수는 배포 패키지의 버전 번호를 문자열로 가져오는 가장 빠른 방법입니다:

>>> version('wheel')
'0.32.3'

배포 파일

importlib.metadata.files(distribution_name)

Return the full set of files contained within the named distribution package.

Raises PackageNotFoundError if the named distribution package is not installed in the current Python environment.

Returns 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, and 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>

일단 파일을 얻으면, 내용을 읽을 수도 있습니다:

>>> print(util.read_text())
import base64
import sys
...
def as_bytes(s):
    if isinstance(s, text_type):
        return s.encode('utf-8')
    return s

You can also use the locate() method to get the absolute path to the file:

>>> util.locate()
PosixPath('/home/gustav/example/lib/site-packages/wheel/util.py')

메타 데이터 파일 목록 파일(RECORD나 SOURCES.txt)이 누락된 경우, files()는 None을 반환합니다. 대상 배포에 메타 데이터가 있음이 알려지지 않았을 때, 이 조건에 대한 보호로 호출자는 files()에 대한 호출을 always_iterable이나 다른 것으로 감쌀 수 있습니다.

배포 요구 사항

importlib.metadata.requires(distribution_name)

Return the declared dependency specifiers for the named distribution package.

Raises PackageNotFoundError if the named distribution package is not installed in the current Python environment.

배포 패키지의 전체 요구 사항을 얻으려면, requires() 함수를 사용하십시오:

>>> 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.

Added in version 3.10.

배포

importlib.metadata.distribution(distribution_name)

Return a Distribution instance describing the named distribution package.

Raises PackageNotFoundError if the named distribution package is not installed in the current Python environment.

class importlib.metadata.Distribution

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.

위에 기술된 모듈 수준 API가 가장 일반적이며 편리한 사용법이지만, Distribution 클래스에서 모든 정보를 얻을 수 있습니다. Distribution은 파이썬 배포 패키지의 메타 데이터를 나타내는 추상 객체입니다. distribution() 함수를 호출해서, 설치된 배포 패키지의 구상 Distribution 서브클래스 인스턴스를 얻을 수 있습니다:

>>> from importlib.metadata import distribution
>>> dist = distribution('wheel')
>>> type(dist)
<class 'importlib.metadata.PathDistribution'>

따라서, 버전 번호를 얻는 다른 방법은 Distribution 인스턴스를 사용하는 것입니다:

>>> dist.version
'0.32.3'

Distribution 인스턴스에서 사용할 수 있는 모든 종류의 추가 메타 데이터가 있습니다:

>>> 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 for additional details.

Added in version 3.13: The .origin property was added.

배포 발견

By default, this package provides built-in support for discovery of metadata for file system and zip file Distribution Packages. 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:

• importlib.metadata does not honor bytes objects on sys.path.

• importlib.metadata will incidentally honor pathlib.Path objects on sys.path even though such values will be ignored for imports.

검색 알고리즘 확장하기

배포 패키지 메타 데이터는 sys.path 검색이나 패키지 로더를 통해 직접 사용할 수 없으므로, 배포의 메타 데이터는 임포트 시스템 파인더를 통해 찾습니다. 배포 패키지의 메타 데이터를 찾기 위해, importlib.metadata는 sys.meta_path의 메타 경로 파인더의 리스트를 조회합니다.

By default 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.

추상 클래스 importlib.abc.MetaPathFinder는 파이썬의 임포트 시스템에 의해 파인더가 기대하는 인터페이스를 정의합니다. importlib.metadata는 sys.meta_path의 파인더에서 선택적인 find_distributions 콜러블을 조회함으로써 이 프로토콜을 확장하고 이 확장된 인터페이스를 다음과 같은 추상 메서드를 정의하는 DistributionFinder 추상 베이스 클래스로 제공합니다:

@abc.abstractmethod
def find_distributions(context=DistributionFinder.Context()):
    """지정한 ``context`` 에 대응하는 패키지에 대한 메타 데이터를 로드할 수 있는
    모든 Distribution 인스턴스의 이터러블을 반환합니다.
    """

DistributionFinder.Context 객체는 검색할 경로와 일치할 이름을 가리키는 .path와 .name 프로퍼티를 제공하고 다른 관련 문맥을 제공할 수 있습니다.

이것이 실제로 의미하는 것은, 파일 시스템이 아닌 위치에서 배포 패키지 메타 데이터를 찾는 것을 지원하려면, Distribution을 서브 클래싱하고 추상 메서드를 구현해야 한다는 것입니다. 그런 다음 사용자 정의 파인더의 find_distributions() 메서드에서, 이 파생된 Distribution의 인스턴스를 반환하십시오.

예제

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. The 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 Distributions 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, and .entry_points attributes.

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.