# Source code for scrapy.loader

    """
    Item Loader

    See documentation in docs/topics/loaders.rst
    """

    from __future__ import annotations

    from typing import TYPE_CHECKING, Any

    import itemloaders

    from scrapy.item import Item
    from scrapy.selector import Selector

    if TYPE_CHECKING:
        from scrapy.http import TextResponse

    class ItemLoader(itemloaders.ItemLoader):
        """
        A user-friendly abstraction to populate an :ref:`item <topics-items>` with data
        by applying :ref:`field processors <topics-loaders-processors>` to scraped data.
        When instantiated with a ``selector`` or a ``response`` it supports
        data extraction from web pages using :ref:`selectors <topics-selectors>`.

        :param item: The item instance to populate using subsequent calls to
            :meth:`~ItemLoader.add_xpath`, :meth:`~ItemLoader.add_css`,
            or :meth:`~ItemLoader.add_value`.
        :type item: :ref:`item object <item-types>`

        :param selector: The selector to extract data from, when using the
            :meth:`add_xpath`, :meth:`add_css`, :meth:`replace_xpath`, or
            :meth:`replace_css` method.
        :type selector: :class:`~scrapy.Selector` object

        :param response: The response used to construct the selector using the
            :attr:`default_selector_class`, unless the selector argument is given,
            in which case this argument is ignored.
        :type response: :class:`~scrapy.http.Response` object

        If no item is given, one is instantiated automatically using the class in
        :attr:`default_item_class`.

        The item, selector, response and remaining keyword arguments are
        assigned to the Loader context (accessible through the :attr:`context` attribute).

        .. attribute:: item

            The item object being parsed by this Item Loader.
            This is mostly used as a property so, when attempting to override this
            value, you may want to check out :attr:`default_item_class` first.

        .. attribute:: context

            The currently active :ref:`Context <loaders-context>` of this Item Loader.

        .. attribute:: default_item_class

            An :ref:`item <topics-items>` class (or factory), used to instantiate
            items when not given in the ``__init__`` method.

        .. attribute:: default_input_processor

            The default input processor to use for those fields which don't specify
            one.

        .. attribute:: default_output_processor

            The default output processor to use for those fields which don't specify
            one.

        .. attribute:: default_selector_class

            The class used to construct the :attr:`selector` of this
            :class:`ItemLoader`, if only a response is given in the ``__init__`` method.
            If a selector is given in the ``__init__`` method this attribute is ignored.
            This attribute is sometimes overridden in subclasses.

        .. attribute:: selector

            The :class:`~scrapy.Selector` object to extract data from.
            It's either the selector given in the ``__init__`` method or one created from
            the response given in the ``__init__`` method using the
            :attr:`default_selector_class`. This attribute is meant to be
            read-only.
        """

        default_item_class: type = Item
        default_selector_class = Selector

        def __init__(
            self,
            item: Any = None,
            selector: Selector | None = None,
            response: TextResponse | None = None,
            parent: itemloaders.ItemLoader | None = None,
            **context: Any,
        ):
            if selector is None and response is not None:
                try:
                    selector = self.default_selector_class(response)
                except AttributeError:
                    selector = None
            context.update(response=response)
            super().__init__(item=item, selector=selector, parent=parent, **context)