How to use the yield function to scrape data from multiple pages - scrapy

Question

I'm trying to scrape data from amazon India website. I am not able collect response and parse the elements using the yield() method when:
1) I have to move from product page to review page
2) I have to move from one review page to another review page
Product page
Review page
Code flow:
1) customerReviewData() calls the getCustomerRatingsAndComments(response)
2) The getCustomerRatingsAndComments(response)
finds the URL of the review page and call the yield request method with getCrrFromReviewPage(request) as callback method, with url of this review page
3) getCrrFromReviewPage() gets new response of the firstreview page and scrape all the elements from the first review page (page loaded) and add it to customerReviewDataList[]
4) get URL of the next page if it exists and recursively call getCrrFromReviewPage() method, and crawl elements from next page, until all the review page is crawled
5) All the reviews gets added to the customerReviewDataList[]
I have tried playing around with yield() changing the parameters and also looked up the scrapy documentation for yield() and Request/Response yield
# -*- coding: utf-8 -*-
import scrapy
import logging
customerReviewDataList = []
customerReviewData = {}
#Get product name in <H1>
def getProductTitleH1(response):
titleH1 = response.xpath('normalize-space(//*[#id="productTitle"]/text())').extract()
return titleH1
def getCustomerRatingsAndComments(response):
#Fetches the relative url
reviewRelativePageUrl = response.css('#reviews-medley-footer a::attr(href)').extract()[0]
if reviewRelativePageUrl:
#get absolute URL
reviewPageAbsoluteUrl = response.urljoin(reviewRelativePageUrl)
yield Request(url = reviewPageAbsoluteUrl, callback = getCrrFromReviewPage())
self.log("yield request complete")
return len(customerReviewDataList)
def getCrrFromReviewPage():
userReviewsAndRatings = response.xpath('//div[#id="cm_cr-review_list"]/div[#data-hook="review"]')
for userReviewAndRating in userReviewsAndRatings:
customerReviewData[reviewTitle] = response.css('#cm_cr-review_list .review-title span ::text').extract()
customerReviewData[reviewDescription] = response.css('#cm_cr-review_list .review-text span::text').extract()
customerReviewDataList.append(customerReviewData)
reviewNextPageRelativeUrl = response.css('#cm_cr-pagination_bar .a-pagination .a-last a::attr(href)')[0].extract()
if reviewNextPageRelativeUrl:
reviewNextPageAbsoluteUrl = response.urljoin(reviewNextPageRelativeUrl)
yield Request(url = reviewNextPageAbsoluteUrl, callback = getCrrFromReviewPage())
class UsAmazonSpider(scrapy.Spider):
name = 'Test_Crawler'
allowed_domains = ['amazon.in']
start_urls = ['https://www.amazon.in/Philips-Trimmer-Cordless-Corded-QT4011/dp/B00JJIDBIC/ref=sr_1_3?keywords=philips&qid=1554266853&s=gateway&sr=8-3']
def parse(self, response):
titleH1 = getProductTitleH1(response),
customerReviewData = getCustomerRatingsAndComments(response)
yield{
'Title_H1' : titleH1,
'customer_Review_Data' : customerReviewData
}
I'm getting the following response:
{'Title_H1': (['Philips Beard Trimmer Cordless and Corded for Men QT4011/15'],), 'customer_Review_Data': <generator object getCustomerRatingsAndComments at 0x048AC630>}
The "Customer_review_Data" should be a list of dict of title and review
I am not able to figure out as to what mistake I am doing here.
When I use the log() or print() to see what data is captured in customerReviewDataList[], unable to see the data in the console either.
I am able to scrape all the reviews in customerReviewDataList[], if they are present in the product page,
In this scenario where I have to use the yield function I am getting the output stated above like this [https://ibb.co/kq8w6cf]
This is the kind of output I am looking for:
{'customerReviewTitle': ['Difficult to find a charger adapter'],'customerReviewComment': ['I already have a phillips trimmer which was only cordless. ], 'customerReviewTitle': ['Good Product'],'customerReviewComment': ['Solves my need perfectly HK']}]}
Any help is appreciated. Thanks in advance.

Answer 1

You should complete the Scrapy tutorial. The Following links section should be specially helpful to you.
This is a simplified version of your code:
def data_request_iterator():
yield Request('https://example.org')
class MySpider(Spider):
name = 'myspider'
start_urls = ['https://example.com']
def parse(self, response):
yield {
'title': response.css('title::text').get(),
'data': data_request_iterator(),
}
Instead, it should look like this:
class MySpider(Spider):
name = 'myspider'
start_urls = ['https://example.com']
def parse(self, response):
item = {
'title': response.css('title::text').get(),
}
yield Request('https://example.org', meta={'item': item}, callback=self.parse_data)
def parse_data(self, response):
item = response.meta['item']
# TODO: Extend item with data from this second response as needed.
yield item