在我的爬虫蜘蛛中,我只想选择带有文本内容的 <p>
:
item['Description'] = response.xpath('//*[@id="textepresentation"]//p[string(.)]').extract()
它工作正常,但不幸的是,这样做,我也会得到空的
<p>
和不间断的空间u'<p>\xa0</p>',
如何避免使用 xpath 选择带有不间断空格的
<p>
? 最佳答案
您可以将 XPath's normalize-space()
字符串函数与几个谓词一起使用:
[normalize-space()]
以便您获得具有非空字符串表示的元素,不包括前导和尾随空格 [not(contains(normalize-space(), "\u00a0"))]
因为 NO-BREAK SPACE
没有被删除(见 this other answer where I checked which ones work ,你可能想添加其他字符来测试) 样本:
>>> import scrapy
>>> selector = scrapy.Selector(text=u'''
... <html>
... <p> </p>
... <p>something</p>
... <p> </p>
... <p><a href="http://example.com">some link</a></p>
... </html>
... ''')
>>> selector.xpath(u'''
... //p[normalize-space()]
... [not(contains(normalize-space(), "\u00a0"))]
... ''').extract()
[u'<p>something</p>', u'<p><a href="http://example.com">some link</a></p>']
>>>
编辑:
在@Kimmy 的回答之后,这里有一个带有 1 个谓词的替代方法,也适用于其他空白字符:
normalize-space()
替换的空白字符 translate()
调用中它是这样的:
>>> chars = '''
... #CHARACTER TABULATION
... #LINE FEED
... #LINE TABULATION
... #FORM FEED
... #CARRIAGE RETURN
... #SPACE
... #NEXT LINE
... NO-BREAK SPACE
... OGHAM SPACE MARK
... MONGOLIAN VOWEL SEPARATOR
... EN QUAD
... EM QUAD
... EN SPACE
... EM SPACE
... THREE-PER-EM SPACE
... FOUR-PER-EM SPACE
... SIX-PER-EM SPACE
... FIGURE SPACE
... PUNCTUATION SPACE
... THIN SPACE
... HAIR SPACE
... ZERO WIDTH SPACE
... ZERO WIDTH NON-JOINER
... ZERO WIDTH JOINER
... LINE SEPARATOR
... PARAGRAPH SEPARATOR
... NARROW NO-BREAK SPACE
... MEDIUM MATHEMATICAL SPACE
... WORD JOINER
... IDEOGRAPHIC SPACE
... ZERO WIDTH NO-BREAK SPACE
... '''
>>> import unicodedata
>>> wsp = [unicodedata.lookup(c)
... for c in chars.splitlines()
... if c.strip() and not c.startswith('#')]
>>>
>>> # somehow NEXT LINE (U+0085) does not work with unicodedata
... wsp.append(u'\u0085')
>>>
>>> selector.xpath(u'''
... //p[normalize-space(translate(., "%(in)s", "%(out)s"))]
... ''' % {'in': ''.join(wsp),
... 'out': ' '*len(wsp)
... }).extract()
[u'<p>something</p>', u'<p><a href="http://example.com">some link</a></p>']
>>>
关于xpath - Scrapy : Select tag with non-breaking space with xpath,我们在Stack Overflow上找到一个类似的问题:https://stackoverflow.com/questions/35364069/