New selector method: extract_first()

I think about suggestion to improve scrapy Selector. I’ve seen this construction in many projects:

result = sel.xpath('//div/text()').extract()[0]

And what about if result: and else:, or try: and except:, which should be always there? When we don’t want ItemLoaders, the most common use of selector is retrieving only single element. Maybe there should be method xpath1 or xpath_one or xpath_first that returns first matched element or None?

[shirk3y]

It also could be like this:

sel.css('span').extract_first()

Maybe it will prevent constructions that aren’t clear much, eg.:

sel.css('span').extract(True)

2014-01-30 Daniel Graña [e-mail]

I think the problem is not in the selecting methods .xpath() and .css()but on .extract(), we can add a parameter to get the first result.

@darkrho https://github.com/darkrho: in #569https://github.com/scrapy/scrapy/pull/569, you propose .get() but it doesn’t extract, instead it returns the first element of a SelectorList that need to call .extract() to get the desired result on this issue:

sel.css(‘span’).get(0).extract()

u’foo’

I would go for something like this:

sel.css(‘span’).extract(first=True) u’<span>foo</span>’

I think the case is always to get the first element, indexing can still be addressed with xpath or css methods.

sel.css(‘span’).extract(takefirst=True) u’<span>foo</span>’

— Reply to this email directly or view it on GitHubhttps://github.com/scrapy/scrapy/issues/568#issuecomment-33690050 .

[curita]

Closed by ff64584