"importlib.metadata" -- Acceso a los metadatos de los paquetes
**************************************************************

Added in version 3.8.

Distinto en la versión 3.10: "importlib.metadata" ya no es
provisional.

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

"importlib.metadata" is a library that provides access to the metadata
of an installed Distribution Package, such as its entry points or its
top-level names (Import Packages, modules, if any). Built in part on
Python's import system, this library intends to replace similar
functionality in the entry point API and metadata API of
"pkg_resources".  Along with "importlib.resources", this package can
eliminate the need to use the older and less efficient "pkg_resources"
package.

"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.

Importante:

  Estos *no* son necesariamente equivalentes o se corresponden 1:1 con
  los nombres de *paquetes de importación* de nivel superior que
  pueden ser importados dentro del código Python. Un *paquete de
  distribución* puede contener múltiples *paquetes de importación* (y
  módulos individuales), y un *paquete de importación* de nivel
  superior puede corresponder a múltiples *paquetes de distribución*
  si es un paquete de espacio de nombres. Puede usar
  package_distributions() para obtener un mapeo entre ellos.

Por defecto, los metadatos de distribución pueden vivir en el sistema
de ficheros o en archivos zip en "sys.path".  A través de un mecanismo
de extensión, los metadatos pueden vivir casi en cualquier lugar.

Ver también:

  https://importlib-metadata.readthedocs.io/
     La documentación de "importlib_metadata", que proporciona un
     backport de "importlib.metadata". Esto incluye una Referencia API
     para las clases y funciones de este módulo, así como una Guía de
     migración para los usuarios existentes de "pkg_resources".


Descripción general
===================

Let's say you wanted to get the version string for a Distribution
Package you've installed using "pip".  We start by creating a virtual
environment and installing something into it:

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

Se puede obtener la cadena de versión para "wheel" ejecutando lo
siguiente:

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

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 objects.

Se pueden obtener los metadatos para una distribución:

   >>> 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']

También se puede obtener el número de versión de una distribución,
enumerar sus archivos constituyentes y obtener una lista de los
Requerimientos de la distribución de la distribución.

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.


API funcional
=============

Este paquete provee la siguiente funcionalidad a través de su API
pública.


Puntos de entrada
-----------------

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.

   Each "EntryPoint" instance has ".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, and ".dist" for obtaining
   information regarding the distribution package that provides the
   entry point.

Consultar todos los puntos de entrada:

   >>> 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')

Elige un script específico llamado "wheel" (que se encuentra en el
proyecto *wheel*):

   >>> 'wheel' in scripts.names
   True
   >>> wheel = scripts['wheel']

De manera equivalente, consulta por ese punto de entrada durante la
selección:

   >>> (wheel,) = entry_points(group='console_scripts', name='wheel')
   >>> (wheel,) = entry_points().select(group='console_scripts', name='wheel')

Inspeccionar el punto de entrada resuelto:

   >>> 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.

*Nota de compatibilidad*

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.


Metadatos de distribución
-------------------------

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.

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 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.*'

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

Distinto en la versión 3.10: La "Descripción" ahora se incluye en los
metadatos cuando se presenta a través de la carga útil. Se han
eliminado los caracteres de continuación de línea.El atributo "json"
fue añadido.


Versiones de distribución
-------------------------

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.

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

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


Archivos de distribución
------------------------

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>

Una vez que se tiene el archivo, también se puede leer su contenido:

   >>> 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')

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.


Requerimientos de la distribución
---------------------------------

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.

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'"]


Mapeo de paquetes de importación a distribución
-----------------------------------------------

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.

Un método práctico para resolver el nombre del Paquete de distribución
(o nombres, en el caso de un paquete de espacio de nombres) que
proporciona cada módulo Python de nivel superior importable o Paquete
de importación:

   >>> packages_distributions()
   {'importlib_metadata': ['importlib-metadata'], 'yaml': ['PyYAML'], 'jaraco': ['jaraco.classes', 'jaraco.functools'], ...}

Algunas instalaciones editables, no suministran nombres de nivel
superior, por lo que esta función no es fiable con dichas
instalaciones.

Added in version 3.10.


Distribuciones
==============

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.

While the module level API described above is the most common and
convenient usage, you can get all of that information from the
"Distribution" class. "Distribution" is an abstract object that
represents the metadata for a Python Distribution Package. You can get
the concrete "Distribution" subclass instance for an installed
distribution package by calling the "distribution()" function:

   >>> 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" instance:

   >>> dist.version
   '0.32.3'

There are all kinds of additional metadata available on "Distribution"
instances:

   >>> 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 PyPA
Core metadata specification for additional details.


Distribution Discovery
======================

Por defecto, este paquete proporciona soporte incorporado para el
descubrimiento de metadatos para el sistema de archivos y archivos zip
Distribution Packages. Este buscador de metadatos busca por defecto
"sys.path", pero varía ligeramente en cómo interpreta esos valores
respecto a cómo lo hace otra maquinaria de importación. En particular:

* "importlib.metadata" does not honor "bytes" objects on "sys.path".

* "importlib.metadata" respetará incidentalmente los objetos
  "pathlib.Path`" en "sys.path" aunque tales valores serán ignorados
  para las importaciones.


Extendiendo el algoritmo de búsqueda
====================================

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".

Por defecto "importlib.metadata" instala un buscador de paquetes de
distribución encontrados en el sistema de ficheros. Este buscador en
realidad no encuentra ninguna *distribución*, pero puede encontrar sus
metadatos.

La clase abstracta "importlib.abc.MetaPathFinder" define la interfaz
que se espera de los buscadores por el sistema de importación de
Python. "importlib.metadata" amplía este protocolo buscando una
"find_distributions" opcional invocable en los buscadores desde
"sys.meta_path" y presenta esta interfaz extendida como la clase base
abstracta "DistributionFinder", que define este método abstracto:

   @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``.
       """

El objeto "DistributionFinder.Context" proporciona propiedades ".path"
y ".name" que indican la ruta de búsqueda y los nombres que deben
coincidir y puede proporcionar otro contexto relevante.

Lo que esto significa en la práctica es que, para soportar la búsqueda
de metadatos en paquetes de distribución en ubicaciones distintas al
sistema de archivos, se debe subclasificar "Distribution" e
implementar sus métodos abstractos. Luego, en el método
"find_distributions()" de un buscador personalizado no hay más que
retornar instancias de esta "Distribution" derivada.
