scrapy xpath not returning desired results. Any idea?

Question

Please look at this page http://164.100.47.132/LssNew/psearch/QResult16.aspx?qref=15845. As you would have guessed, I am trying to scrape all the fields on this page. All fields are yield-ed properly except the Answer field. What I find odd is that the page structure for the question and answer is almost the same (Table[1] and Table[2]); the question scrapes perfectly but the Answer does not. Here are my xpaths:

question:

['q_main'] = Selector(response).xpath('//*[@id="ctl00_ContPlaceHolderMain_GridView2"]/tbody/tr/td/table[1]/tbody/tr/td/text()').extract()

works perfect

Answer:

['q_answer'] = Selector(response).xpath('//*[@id="ctl00_ContPlaceHolderMain_GridView2"]/tbody/tr/td/table[2]/tbody/tr[2]/td/text()').extract()

returns a blank. I have reproduced the full xpath, as returned by/verified in Xpath Helper and console. What am i overlooking? What am I not able to see?

Answer 1

seems like your xpath has some problem,

checkout the demo from scrapy shell,

In [1]: response.xpath('//tr[td[@class="mainheaderq" and contains(font/text(), "ANSWER")]]/following-sibling::tr/td[@class="griditemq"]//text()').extract()
Out[1]: 
[u'\r\n\r\n',
 u'MINISTER OF STATE(I/C) FOR COAL, POWER AND NEW & RENEWABLE ENERGY   (SHRI PIYUSH GOYAL)\r\n\r\n ',
 u'(a) & (b): So far 29 coal mines have been auctioned under the provisions of Coal Mines (Special Provisions) \r\nAct, 2015 and the Rules made thereunder. The auction process for non-regulated sector viz. Iron and Steel, \r\nCement and Captive Power was based on forward bidding process where bidders had to submit their final price \r\noffer above the applicable floor price. In case of Power sector which is a regulated one, reverse bidding \r\nmethodology was adopted where bidders had to submit bids below the applicable ceiling price, which shall be \r\ntaken as fuel cost in determination of power tariff. In case, bid price reaches Rs. zero in reverse bidding, \r\nthe bidding is based on additional premium payable to the concerned State Government, over and  above  the  \r\nfixed  reserve  price  of  Rs. 100/-  per  tonne.\r\n\r\n',
 u'\r\nRevenue which would accrue to the coal bearing State Government concerned comprises of Upfront payment \r\nas prescribed in the tender document, Auction proceeds and Royalty on per tonne of coal production. State-wise \r\ndetails of 29 coal mines auctioned so far along-with specified end-uses and estimated revenue which would accrue \r\nto coal bearing state during the life of mine/lease period as given below:\r\n',
 u'\r\n\r\nS.No\tState\t\tSpecified End \u2013Use\t\t\tName of Coal Mine\t\tEstimated Revenueduring \r\n\t\t\t\t\t\t\t\t\t\t\t\tthe life of mine/lease \r\n\t\t\t\t\t\t\t\t\t\t\t\tperiod (Rs. In Crores)\r\n1\tChattishgarh\tNon-Regualted Sector\t\t\tChotia\t\t\t\t51596\r\n\t\t\t\t\t\t\t\tGare Palma IV-4\t\r\n\t\t\t\t\t\t\t\tGare Palma IV-5\t\r\n\t\t\t\t\t\t\t\tGare Palma IV-7\t\r\n\t\t\t\t\t\t\t\tGare-Palma Sector-IV/8\r\n2\tJharkhand\tNon-Regualted Sector\t\t\tBrinda and Sasai\t\t49272\r\n\t\t\t\t\t\t\t\tDumri\r\n\t\t\t\t\t\t\t\tKathautia\r\n\t\t\t\t\t\t\t\tLohari\r\n\t\t\t\t\t\t\t\tMeral\r\n\t\t\t\t\t\t\t\tMoitra\r\n\t\t\tPower\t\t\t\t\tGaneshpur\r\n\t\t\t\t\t\t\t\tJitpur\r\n\t\t\t\t\t\t\t\tTokisud North\r\n3\tMadhya Pradesh\tNon-Regualted Sector\t\t\tBicharpur\t\t\t42811\r\n\t\t\t\t\t\t\t\tMandla North\r\n\t\t\t\t\t\t\t\tMandla-South\r\n\t\t\t\t\t\t\t\tSialGhoghri\r\n\t\t\tPower\t\t\t\t\tAmelia North\r\n4\tMaharashtra\tNon-Regualted Sector\t\t\tBelgaon\t\t\t\t2738\r\n\t\t\t\t\t\t\t\tMarkiMangli III\r\n\t\t\t\t\t\t\t\tNerad Malegaon\r\n5\tOdisha\t\tPower\t\t\t\t\tMandakini\t\t\t33741\r\n\t\t\t\t\t\t\t\tTalabira-I\r\n\t\t\t\t\t\t\t\tUtkal - C\r\n6\tWest Bengal\tNon-Regualted Sector\t\t\tArdhagram\t\t\t13354\r\n\t\t\tPower\t\t\t\t\tSarisatolli\r\n\t\t\t\t\t\t\t\tTrans Damodar\r\n\tTotal\t\t\t\t\t\t\t(29) coal blocks\t\t193512\r\n',
 u'\r\n\r\n\r\nCoal mine has been assigned to successful bidder as Designated Custodian in view of a court case.\r\n\r\n',
 u'\r\nIn addition, an estimated amount of Rs. 1,41,854 Crores would accrue to coal bearing States from allotment \r\nof 38 coal mines to Central and State PSU\u2019s.\r\n\r\n',
 u'Out of these 29 coal mines, 16 are operational coal mines included in Schedule-II of the Act and 13 are \r\nnon-operational included in Schedule-III of the Act. Milestones for development and production of coal \r\nfrom the auctioned coal mines have been prescribed under the Coal Mines Development and Production Agreement \r\nsigned with the Successful Bidder. \r\n\r\n ',
 u'(c) & (d): Yes, Sir. A few complaints were received regarding cartelization in bidding. It is not possible to \r\nconclusively establish the same until investigation are carried out by Competent Authority. ',
 u'\r\n\r\n\r\nThe Government has not approved the recommendation of NA for declaration of successful bidder in case of \r\n4 coal mines namely Gare Palma IV/2&3, Gare Palma IV/1 and Tara as final closing bid price was not found \r\nto be reflecting fair value.  ',
 u'\r\n\r\n\r\n']

when you are dealing with the tables sometimes it happens and for more information you can refer this.

Answer 2

At least part of the source of your difficulty lies in the fact that the code you see in the console is not the source html that your spider gets as a response (and on which the selectors operate). In particular, it is extremely common for a <table> to not include a <tbody>; but when your browser translates the html to the DOM tree, it slaps in <tbody> tags. And there was a time when much of the layout of webpages was actually accomplished with (crazily) nested tables. As a result, the DOM of such a website will typically have many more <tbody> elements than the html source.

What this means in practical terms is that:

1. It is generally a good idea to find a relatively simple xpath (or CSS selector, or ...) for the element(s) you want to select -- not the behemoth you sometimes get from your developer tools.
2. It is generally a bad idea to include /tbody in your xpath (unless there is an associated attribute, indicating that the tag exists in the source html).

For the site in question,

 response.xpath('//td[@class="griditemq"]').extract()

returns a list with the first element the question and the second element the answer.