尝试用scrapy（0.16）控制台解析this rss feed没有按预期工作，我不知道出了什么问题。似乎只有@href等属性可以访问：
>>> fetch('http://www2c.cdc.gov/podcasts/feed.asp?feedid=183')
2014-10-23 12:20:54-0400 [default] DEBUG: Crawled (200) <GET http://www2c.cdc.go
v/podcasts/feed.asp?feedid=183> (referer: None)
[s] Available Scrapy objects:
[s] item {}
[s] request <GET http://www2c.cdc.gov/podcasts/feed.asp?feedid=183>
[s] response <200 http://www2c.cdc.gov/podcasts/feed.asp?feedid=183>
[s] settings <CrawlerSettings module=<module 'ebola.scraper.scrape.settings'
from 'ebola\scraper\scrape\settings.pyc'>>
[s] spider <BaseSpider 'default' at 0x3efc130>
[s] xxs <XmlXPathSelector xpath=None data=u'<feed xmlns="http://www.w3.
org/2005/Atom'>
[s] Useful shortcuts:
[s] shelp() Shell help (print this help)
[s] fetch(req_or_url) Fetch request (or URL) and update local objects
[s] view(response) View response in a browser
>>> xxs.select("//entry").extract()
[]
>>> xxs.select("//link").extract()
[]
>>> xxs.select("//link/text()").extract()
[]
>>> xxs.select("//title").extract()
[]
>>> xxs.select("//title/text()").extract()
[]
>>> xxs.select("//link/@href").extract()
[]
>>> xxs.select("//@href").extract()
[u'http://www2c.cdc.gov/podcasts/feed.asp?feedid=183', u'http://www.cdc.gov/medi
a/index.html', u'http://www2c.cdc.gov/podcasts/download.asp?af=h&f=8634459', u'h
ttp://www.cdc.gov/media/releases/2014/images/p1022-post-arrival-monitoring-300x2
00.jpg', u'http://www2c.cdc.gov/podcasts/download.asp?af=h&f=8634458', u'http://
www2c.cdc.gov/podcasts/download.asp?af=h&f=8634453', u'http://www2c.cdc.gov/podc
asts/download.asp?af=h&f=8634436', u'http://www2c.cdc.gov/podcasts/download.asp?
af=h&f=8634435', u'http://www2c.cdc.gov/podcasts/download.asp?af=h&f=8634434', u
'http://www2c.cdc.gov/podcasts/download.asp?af=h&f=8634417', u'http://www2c.cdc.
gov/podcasts/download.asp?af=h&f=8634403', u'http://www2c.cdc.gov/podcasts/downl
oad.asp?af=h&f=8634373', u'http://www2c.cdc.gov/podcasts/download.asp?af=h&f=863
4367', u'http://www2c.cdc.gov/podcasts/download.asp?af=h&f=8634365', u'http://ww
w2c.cdc.gov/podcasts/download.asp?af=h&f=8634362', u'http://www2c.cdc.gov/podcas
ts/download.asp?af=h&f=8634361', u'http://www2c.cdc.gov/podcasts/download.asp?af
=h&f=8634355', u'http://www2c.cdc.gov/podcasts/download.asp?af=h&f=8634350', u'h
ttp://www2c.cdc.gov/podcasts/download.asp?af=h&f=8634349', u'http://www2c.cdc.go
v/podcasts/download.asp?af=h&f=8634330', u'http://www2c.cdc.gov/podcasts/downloa
d.asp?af=h&f=8634329', u'http://www2c.cdc.gov/podcasts/download.asp?af=h&f=86343
28', u'http://www2c.cdc.gov/podcasts/download.asp?af=h&f=8634325', u'http://www2
c.cdc.gov/podcasts/download.asp?af=h&f=8634324', u'http://www2c.cdc.gov/podcasts
/download.asp?af=h&f=8634322', u'http://www2c.cdc.gov/podcasts/download.asp?af=h
&f=8634283', u'http://www2c.cdc.gov/podcasts/download.asp?af=h&f=8634278', u'htt
p://www2c.cdc.gov/podcasts/download.asp?af=h&f=8634277', u'http://www2c.cdc.gov/
podcasts/download.asp?af=h&f=8634273', u'http://www2c.cdc.gov/podcasts/download.
asp?af=h&f=8634265', u'http://www2c.cdc.gov/podcasts/download.asp?af=h&f=8634262
', u'http://www2c.cdc.gov/podcasts/download.asp?af=h&f=8634250', u'http://www2c.
cdc.gov/podcasts/download.asp?af=h&f=8634251', u'http://www.cdc.gov/media/DPK/20
14/images/vs-crash-injuries/fb.jpg', u'http://www2c.cdc.gov/podcasts/download.as
p?af=h&f=8634248', u'http://www2c.cdc.gov/podcasts/download.asp?af=h&f=8634234',
u'http://www2c.cdc.gov/podcasts/download.asp?af=h&f=8634233', u'http://www2c.cd
c.gov/podcasts/download.asp?af=h&f=8634225', u'http://www2c.cdc.gov/podcasts/dow
nload.asp?af=h&f=8634224', u'http://www2c.cdc.gov/podcasts/download.asp?af=h&f=8
634222', u'http://www2c.cdc.gov/podcasts/download.asp?af=h&f=8634221', u'http://
www2c.cdc.gov/podcasts/download.asp?af=h&f=8634323', u'http://www2c.cdc.gov/podc
asts/download.asp?af=h&f=8634217', u'http://www2c.cdc.gov/podcasts/download.asp?
af=h&f=8634214', u'http://www2c.cdc.gov/podcasts/download.asp?af=h&f=8634178', u
'http://www2c.cdc.gov/podcasts/download.asp?af=h&f=8634174', u'http://www.cdc.go
v/media/images/L2/p1002-smoke-free-housing.jpg', u'http://www2c.cdc.gov/podcasts
/download.asp?af=h&f=8634173', u'http://www2c.cdc.gov/podcasts/download.asp?af=h
&f=8634211', u'http://www2c.cdc.gov/podcasts/download.asp?af=h&f=8634164', u'htt
p://www2c.cdc.gov/podcasts/download.asp?af=h&f=8634157', u'http://www2c.cdc.gov/
podcasts/download.asp?af=h&f=8634160', u'http://www2c.cdc.gov/podcasts/download.
asp?af=h&f=8634161', u'http://www2c.cdc.gov/podcasts/download.asp?af=h&f=8634146
', u'http://www2c.cdc.gov/podcasts/download.asp?af=h&f=8634073']
>>>
请记住改变版本的scrapy不是一个选项，我锁定为0.16任何想法都赞赏...
答案 0 :(得分：2)
当您在浏览器中查看HTML源代码时，您会看到源XML位于默认命名空间中：
<feed xmlns="http://www.w3.org/2005/Atom">
feed的所有后代元素也属于此命名空间 - 这就是您的选择器不会产生任何结果的原因。除了选择属性的那个：
似乎只有@href等属性可以访问
因为属性不采用默认命名空间 - 并且没有名称空间。
如果您想访问命名空间中的元素，则必须首先注册所述命名空间，并为其选择前缀：
xxs.register_namespace("atom", "http://www.w3.org/2005/Atom")
然后，使用atom:（或任何其他前缀）为元素添加前缀：
xxs.select("//atom:link").extract()