How to enable overwriting a file everytime in scrapy item export?

问题

I am scraping a website which returns in a list of urls. Example - scrapy crawl xyz_spider -o urls.csv

It is working absolutely fine now I want is to make new urls.csv not append data into the file. Is there any parameter passing I can do to make it enable?

回答1:

Unfortunately scrapy can't do this at the moment.
There is a proposed enhancement on github though: https://github.com/scrapy/scrapy/issues/547

However you can easily do redirect the output to stdout and redirect that to a file:

scrapy crawl myspider -t json --nolog -o - > output.json

-o - means output to minus and minus in this case means stdout.
You can also make some aliases to delete the file before running scrapy, something like:

alias sc='-rm output.csv && scrapy crawl myspider -o output.csv'

回答2:

I usually tackle custom file exports by running Scrapy as a python script and opening a file before calling up the Spider Class. This gives greater flexibility with handling and formatting your csv files and even running them as a extension to a web-app or running them the cloud. Something in the lines of the following:

import csv

if __name__ == '__main__':            
        process = CrawlerProcess()

        with open('Output.csv','wb') as output_file:
            mywriter = csv.write(output_file)
            process.crawl(Spider_Class, start_urls = start_urls)
            process.start() 
            process.close()                             

回答3:

You can open the file and close it so it will remove the content of the file.

class RestaurantDetailSpider(scrapy.Spider):

    file = open('./restaurantsLink.csv','w')
    file.close()
    urls = list(open('./restaurantsLink.csv')) 
    urls = urls[1:]
    print "Url List Found : " + str(len(urls))

    name = "RestaurantDetailSpider"
    start_urls = urls

    def safeStr(self, obj):
        try:
            if obj == None:
                return obj
            return str(obj)
        except UnicodeEncodeError as e:
            return obj.encode('utf8', 'ignore').decode('utf8')
        return ""

    def parse(self, response):
        try :
            detail = RestaurantDetailItem()
            HEADING = self.safeStr(response.css('#HEADING::text').extract_first())
            if HEADING is not None:
                if ',' in HEADING:
                    HEADING = "'" + HEADING + "'"
                detail['Name'] = HEADING

            CONTACT_INFO = self.safeStr(response.css('.directContactInfo *::text').extract_first())
            if CONTACT_INFO is not None:
                if ',' in CONTACT_INFO:
                    CONTACT_INFO = "'" + CONTACT_INFO + "'"
                detail['Phone'] = CONTACT_INFO

            ADDRESS_LIST = response.css('.headerBL .address *::text').extract()
            if ADDRESS_LIST is not None:
                ADDRESS = ', '.join([self.safeStr(x) for x in ADDRESS_LIST])
                ADDRESS = ADDRESS.replace(',','')
                detail['Address'] = ADDRESS

            EMAIL = self.safeStr(response.css('#RESTAURANT_DETAILS .detailsContent a::attr(href)').extract_first())
            if EMAIL is not None:
                EMAIL = EMAIL.replace('mailto:','')
                detail['Email'] = EMAIL

            TYPE_LIST = response.css('.rating_and_popularity .header_links *::text').extract()
            if TYPE_LIST is not None:
                TYPE = ', '.join([self.safeStr(x) for x in TYPE_LIST])
                TYPE = TYPE.replace(',','')
                detail['Type'] = TYPE

            yield detail
        except Exception as e:
            print "Error occure"
            yield None

    scrapy crawl RestaurantMainSpider  -t csv -o restaurantsLink.csv

this will create the restaurantsLink.csv file which I am using in my next spider RestaurantDetailSpider.

So you can run the following command -- it will remove and create a new file restaurantsLink.csv which we are going to use in the above spider and it will be overridden whenever we run the spider:

rm restaurantsLink.csv && scrapy crawl RestaurantMainSpider -o restaurantsLink.csv -t csv

来源：https://stackoverflow.com/questions/40327665/how-to-enable-overwriting-a-file-everytime-in-scrapy-item-export