# `importlib.metadata` – 패키지 메타데이터 액세스

버전 3.8에 추가.

버전 3.10에서 변경: `importlib.metadata`는 더는 잠정적이지 않습니다.

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

`importlib.metadata`는 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_resources`의 진입 지점 API와 메타데이터 API에서 유사한 기능을 대체하려고 합니다. `importlib.resources`와 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 package_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

`pip`를 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 `wheel`에 대한 버전 문자열을 얻을 수 있습니다:

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

`console_scripts`, `distutils.commands`나 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.

## 기능적 API

이 패키지는 공용 API를 통해 다음과 같은 기능을 제공합니다.

### 진입 지점

The `entry_points()` function returns a collection of entry points. Entry points are represented by `EntryPoint` instances; each `EntryPoint` has a `.name`, `.group`, and `.value` attributes and a `.load()` method to resolve the value. There are also `.module`, `.attr`, and `.extras` attributes for getting the components of the `.value` attribute.

모든 진입 지점을 조회합니다:

    >>> eps = entry_points()

The `entry_points()` function returns an `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>

`group`과 `name`은 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.

Compatibility Note

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. For compatibility, if no parameters are passed to entry_points, a `SelectableGroups` object is returned, implementing that dict interface. In the future, calling `entry_points` with no parameters will return an `EntryPoints` object. Users should rely on the selection interface to retrieve entry points by group.

### 배포 메타데이터

Every Distribution Package includes some metadata, which you can extract using the `metadata()` function:

    >>> wheel_metadata = metadata('wheel')

The keys of the returned data structure, a `PackageMetadata`, name the metadata keywords, and the values are returned unparsed from the distribution metadata:

    >>> 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.*'

참고

The actual type of the object returned by `metadata()` is an implementation detail and should be accessed only through the interface described by the PackageMetadata protocol.

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

The `version()` function is the quickest way to get a Distribution Package’s version number, as a string:

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

### 배포 파일

You can also get the full set of files contained within a distribution. The `files()` function takes a Distribution Package name and returns all of the files installed by this distribution. Each file object returned is a `PackagePath`, a `pathlib.PurePath` derived object with additional `dist`, `size`, and `hash` properties as indicated by the metadata. 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 a 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()` will return `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.

### 배포 요구 사항

To get the full set of requirements for a Distribution Package, use the `requires()` function:

    >>> requires('wheel')
    ["pytest (>=3.0.0) ; extra == 'test'", "pytest-cov ; extra == 'test'"]

### Mapping import to distribution packages

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'], ...}

버전 3.10에 추가.

## 배포

While the above API is the most common and convenient usage, you can get all of that information from the `Distribution` class. A `Distribution` is an abstract object that represents the metadata for a Python Distribution Package. You can get the `Distribution` instance:

    >>> from importlib.metadata import distribution
    >>> dist = distribution('wheel')

Thus, an alternative way to get the version number is through the `Distribution` instance:

    >>> dist.version
    '0.32.3'

There are all kinds of additional metadata available on the `Distribution` instance:

    >>> dist.metadata['Requires-Python']
    '>=2.7, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*'
    >>> dist.metadata['License']
    'MIT'

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

## 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

Because 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 meta path finders on `sys.meta_path`.

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.MetaPathFinder`는 파이썬의 임포트 시스템에 의해 파인더가 기대하는 인터페이스를 정의합니다. `importlib.metadata`는 `sys.meta_path`의 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()):
        """Return an iterable of all Distribution instances capable of
        loading the metadata for packages for the indicated ``context``.
        """

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

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