Get tr having specific th value from the table having an id using Xpath - python-3.x

Question

I am using python3.6 with XPath library. Crawling inside the table gives me an empty list. And need to crawl to specific th.
My tr contents are dynamically generated. I need to crawl to tr which has a specific th value. Example In HTML code, the Rank appears in the second tr but it can appear in anywhere in tr. It doesn't have a specific index. Need to get the href from the tr having the Rank th.
My html file:
<tbody>
<tr>
<th class="a-color-secondary a-size-base prodDetSectionEntry">
Product Number
</th>
<td class="a-size-base">
B003NR57BY
</td>
</tr>
<tr>
<th class="a-color-secondary a-size-base prodDetSectionEntry">
Rank
</th>
<td>
<span>
<span>#3 in Computer Mice</span>
<br>
</span>
</td>
</tr>
<tr>
<th class="a-color-secondary a-size-base prodDetSectionEntry">
Created Date
</th>
<td class="a-size-base">
June 7, 2010
</td>
</tr>
</tbody>
</table>
Python code:
listings_details = parser.xpath(XPATH_PRODUCT_DETAILS)
for row in listings_details:
th = row.xpath("./th/text()")
if th[0].strip() == 'Rank':
categories = row.xpath("./td/span/span//text()")
qid_url= row.xpath("./td/span/span//#href")
I expect the output to be
Rank: 3,
url : /gp/bestsellers/pc/11036491/ref=pd_zg_hrsr_pc_1_1_last,
category: Computer Mice

Answer 1

Need to get the href from the tr having the Rank th.
Use:
/table/tbody/tr[normalize-space(th)='Rank']/td//a/#href
Note: this works for your provided fragment (now well-formed). You need to add later a context for selecting the table element.
<table>
<tbody>
<tr>
<th class="a-color-secondary a-size-base prodDetSectionEntry">Product Number</th>
<td class="a-size-base">B003NR57BY</td>
</tr>
<tr>
<th class="a-color-secondary a-size-base prodDetSectionEntry">Rank</th>
<td>
<span>
<span>#3 in
Computer Mice
</span>
<br/>
</span>
</td>
</tr>
<tr>
<th class="a-color-secondary a-size-base prodDetSectionEntry">Created Date</th>
<td class="a-size-base">June 7, 2010</td>
</tr>
</tbody>
</table>
Test in http://www.xpathtester.com/xpath/53808ee94dfbc5b38f12791cf857ffb9