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76 lines
2.5 KiB
ReStructuredText
76 lines
2.5 KiB
ReStructuredText
======= =========================================
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SEP 06
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Title Extractors
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Author Ismael Carnales and a bunch of rabid mice
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Created 2009-07-28
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Status Obsolete (discarded)
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======= =========================================
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==========================================
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SEP-006: Rename of Selectors to Extractors
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==========================================
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This SEP proposes a more meaningful naming of XPathSelectors or "Selectors" and their `x` method.
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Motivation
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==========
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When you use Selectors in Scrapy, your final goal is to "extract" the data that
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you've selected, as the [http://doc.scrapy.org/en/latest/topics/selectors.html
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XPath Selectors documentation] says (bolding by me):
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When you’re scraping web pages, the most common task you need to perform is
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to **extract** data from the HTML source.
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..
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Scrapy comes with its own mechanism for **extracting** data. They’re called
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``XPath`` selectors (or just “selectors”, for short) because they “select”
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certain parts of the HTML document specified by ``XPath`` expressions.
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..
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To actually **extract** the textual data you must call the selector
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``extract()`` method, as follows
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..
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Selectors also have a ``re()`` method for **extracting** data using regular
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expressions.
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..
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For example, suppose you want to **extract** all <p> elements inside <div>
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elements. First you get would get all <div> elements
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Rationale
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=========
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As and there is no ``Extractor`` object in Scrapy and what you want to finally
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perform with ``Selectors`` is extracting data, we propose the renaming of
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``Selectors`` to ``Extractors``. (In Scrapy for extracting you use selectors is
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really weird :) )
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Additional changes
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==================
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As the name of the method for performing selection (the ``x`` method) is not
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descriptive nor mnemotechnic enough and clearly clashes with ``extract`` method
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(x sounds like a short for extract in english), we propose to rename it to
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`select`, `sel` (is shortness if required), or `xpath` after `lxml's
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<http://codespeak.net/lxml/xpathxslt.html>`_ ``xpath`` method.
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Bonus (ItemBuilder)
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===================
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After this renaming we propose also renaming ``ItemBuilder`` to ``ItemExtractor``,
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because the ``ItemBuilder``/``Extractor`` will act as a bridge between a set of
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``Extractors`` and an ``Item`` and because it will literally "extract" an item from a
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webpage or set of pages.
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References
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==========
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1. XPath Selectors (http://doc.scrapy.org/topics/selectors.html)
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2. XPath and XSLT with lxml (http://codespeak.net/lxml/xpathxslt.html)
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