Scrapy and XPath issue with nested Xpaths - xpath

Question

I'm trying to read Amazon products into scrapy.
Starting from a random category using this XPath:
products = Selector(response).xpath('//div[#class="s-item-container"]')
for product in products:
item = AmzItem()
item['title'] = product.xpath('//a[#class="s-access-detail-page"]/#title').extract()[0]
item['url'] = product.xpath('//a[#class="s-access-detail-page"]/#href').extract()[0]
yield item
('//div[#class="s-item-container"]') returns all the divs with the products on one category page - that's correct.
Now, how would I get the link to the product?
// stands for where ever in the code
a with the #class should select the right class
But I get a:
item['title'] = product.xpath('//a[#class="s-access-detail-page"]/#title').extract()[0]
exceptions.IndexError: list index out of range
So my list matching this XPath must be empty - but I don't understand why?
EDIT:
The HTML would look like that:
<div class="s-item-container" style="height: 343px;">
<div class="a-row a-spacing-base">
<div class="a-column a-span12 a-text-left">
<div class="a-section a-spacing-none a-inline-block s-position-relative">
<a class="a-link-normal a-text-normal" href="https://rads.stackoverflow.com/amzn/click/com/B0105S434A" rel="nofollow noreferrer"><img alt="Product Details" src="http://ecx.images-amazon.com/images/I/41%2BzrAY74UL._AA160_.jpg" onload="viewCompleteImageLoaded(this, new Date().getTime(), 24, false);" class="s-access-image cfMarker" height="160" width="160"></a>
<div class="a-section a-spacing-none a-text-center">
<div class="a-row a-spacing-top-mini">
<a class="a-size-mini a-link-normal a-text-normal" href="https://rads.stackoverflow.com/amzn/click/com/B0105S434A" rel="nofollow noreferrer">
<div class="a-box">
<div class="a-box-inner a-padding-mini"><span class="a-color-secondary">See more choices</span></div>
</div>
</a>
</div>
</div>
</div>
</div>
</div>
<div class="a-row a-spacing-mini">
<div class="a-row a-spacing-none">
<a class="a-link-normal s-access-detail-page a-text-normal" title="Harry Potter Gryffindor School Fancy Robe Cloak Costume And Tie (Size S)" href="https://rads.stackoverflow.com/amzn/click/com/B0105S434A" rel="nofollow noreferrer">
<h2 class="a-size-base a-color-null s-inline s-access-title a-text-normal">Harry Potter Gryffindor School Fancy Robe Cloak Costume And Tie (Size S)</h2>
</a>
</div>
<div class="a-row a-spacing-mini"><span class="a-size-small a-color-secondary">by </span><span class="a-size-small a-color-secondary">Legend</span></div>
</div>
<div class="a-row a-spacing-mini">
<div class="a-row a-spacing-none"><a class="a-size-small a-link-normal a-text-normal" href="http://www.amazon.com/gp/offer-listing/B0105S434A/ref=sr_1_21_olp?s=pet-supplies&ie=UTF8&qid=1435391788&sr=1-21&keywords=pet+supplies&condition=new"><span class="a-size-base a-color-price a-text-bold">$28.99</span><span class="a-letter-space"></span>new<span class="a-letter-space"></span><span class="a-color-secondary">(1 offer)</span><span class="a-letter-space"></span><span class="a-color-secondary a-text-strike"></span></a></div>
</div>
<div class="a-row a-spacing-none"><span name="B0105S434A">
<span class="a-declarative" data-action="a-popover" data-a-popover="{"max-width":"700","closeButton":"false","position":"triggerBottom","url":"/review/widgets/average-customer-review/popover/ref=acr_search__popover?ie=UTF8&asin=B0105S434A&contextId=search&ref=acr_search__popover"}"><i class="a-icon a-icon-star a-star-4"><span class="a-icon-alt">3.9 out of 5 stars</span></i><i class="a-icon a-icon-popover"></i></span></span>
<a class="a-size-small a-link-normal a-text-normal" href="https://rads.stackoverflow.com/amzn/click/com/B0105S434A" rel="nofollow noreferrer">48</a>
</div>
</div>

Answer 1

It should be:
# ------------- The dot makes the query relative to product
product.xpath('.//a[#class="s-access-detail-page"]/#title')

Answer 2

//a[#class="s-access-detail-page"] requires to be exactly class="s-access-detail-page", because xpath works with string but not with meaning :) When you have "multi class ", use contains function
//a[contains(concat(' ', #class, ' '), " s-access-detail-page ")]/#title