scrapy/sep/sep-006.rst

=======  =========================================
SEP      06
Title    Extractors
Author   Ismael Carnales and a bunch of rabid mice
Created  2009-07-28
Status   Obsolete (discarded)
=======  =========================================

==========================================
SEP-006: Rename of Selectors to Extractors
==========================================

This SEP proposes a more meaningful naming of XPathSelectors or "Selectors" and
their ``x`` method.

Motivation
==========

When you use Selectors in Scrapy, your final goal is to "extract" the data that
you've selected, as the [https://docs.scrapy.org/en/latest/topics/selectors.html
XPath Selectors documentation] says (bolding by me):

   When you’re scraping web pages, the most common task you need to perform is
   to **extract** data from the HTML source.

..

   Scrapy comes with its own mechanism for **extracting** data. They’re called
   ``XPath`` selectors (or just “selectors”, for short) because they “select”
   certain parts of the HTML document specified by ``XPath`` expressions.

..

   To actually **extract** the textual data you must call the selector
   ``extract()`` method, as follows

..

   Selectors also have a ``re()`` method for **extracting** data using regular
   expressions.

..

   For example, suppose you want to **extract** all <p> elements inside <div>
   elements. First you get would get all <div> elements

Rationale
=========

As and there is no ``Extractor`` object in Scrapy and what you want to finally
perform with ``Selectors`` is extracting data, we propose the renaming of
``Selectors`` to ``Extractors``. (In Scrapy for extracting you use selectors is
really weird :) )

Additional changes
==================

As the name of the method for performing selection (the ``x`` method) is not
descriptive nor mnemotechnic enough and clearly clashes with ``extract`` method
(x sounds like a short for extract in english), we propose to rename it to
``select``, ``sel`` (is shortness if required), or ``xpath`` after `lxml's
<http://lxml.de/xpathxslt.html>`_ ``xpath`` method.

Bonus (ItemBuilder)
===================

After this renaming we propose also renaming ``ItemBuilder`` to ``ItemExtractor``,
because the ``ItemBuilder``/``Extractor`` will act as a bridge between a set of
``Extractors`` and an ``Item`` and because it will literally "extract" an item from a
webpage or set of pages.

References
==========

 1. XPath Selectors (https://docs.scrapy.org/topics/selectors.html)
 2. XPath and XSLT with lxml (http://lxml.de/xpathxslt.html)