python - How to loop through multiple URLs to scrape from a CSV file in Scrapy?

Question

My code for scrapping data from alibaba website:

import scrapy




class IndiamartSpider(scrapy.Spider):
    name = 'alibot'
    allowed_domains = ['alibaba.com']
    start_urls = ['https://www.alibaba.com/showroom/acrylic-wine-box_4.html']


    def parse(self, response):
        Title = response.xpath('//*[@class="title three-line"]/a/@title').extract()
        Price = response.xpath('//div[@class="price"]/b/text()').extract()
        Min_order = response.xpath('//div[@class="min-order"]/b/text()').extract()
        Response_rate = response.xpath('//i[@class="ui2-icon ui2-icon-skip"]/text()').extract()

        for item in zip(Title,Price,Min_order,Response_rate):
            scraped_info = {
                'Title':item[0],
                'Price': item[1],
                'Min_order':item[2],
                'Response_rate':item[3]

            }
            yield scraped_info

Notice the start url, it only scraps through the given URL, but i want this code to scrap all the urls present in my csv file. My csv file contains large amount of URLs. Sample of the data.csv file::

'https://www.alibaba.com/showroom/shock-absorber.html',
'https://www.alibaba.com/showroom/shock-wheel.html',
'https://www.alibaba.com/showroom/shoes-fastener.html',
'https://www.alibaba.com/showroom/shoes-women.html',
'https://www.alibaba.com/showroom/shoes.html',
'https://www.alibaba.com/showroom/shoulder-long-strip-bag.html',
'https://www.alibaba.com/showroom/shower-hair-band.html',
...........

How do i import all the links of csv file in the code at once?

Answer 1

To correctly loop through a file without loading all of it into memory you should use generators, as both file objects and start_requests method in python/scrapy are generators:

class MySpider(Spider):
    name = 'csv'

    def start_requests(self):
        with open('file.csv') as f:
            for line in f:
                if not line.strip():
                    continue
                yield Request(line)

To explain futher: Scrapy engine uses start_requests to generate requests as it goes. It will keep generating requests untill concurrent request limit is full (settings like CONCURRENT_REQUESTS).
Also worth noting that by default scrapy crawls depth first - newer requests take priority, so start_requests loop will be last to finish.