yield scrapy.Request 不會在每次迭代時調用 parse function

Question

在我的代碼中，我必須在 scrapy class 中運行。start_request 從 excel 工作簿中獲取數據並將值plate_num_xlsx變量。

def start_requests(self):
    df=pd.read_excel('data.xlsx')
    columnA_values=df['PLATE']
    for row in columnA_values:
        global  plate_num_xlsx
        plate_num_xlsx=row
        print("+",plate_num_xlsx)
        base_url =f"https://dvlaregistrations.dvla.gov.uk/search/results.html?search={plate_num_xlsx}&action=index&pricefrom=0&priceto=&prefixmatches=&currentmatches=&limitprefix=&limitcurrent=&limitauction=&searched=true&openoption=&language=en&prefix2=Search&super=&super_pricefrom=&super_priceto="
        url=base_url
        yield scrapy.Request(url,callback=self.parse)

但是，在每次迭代中，它應該調用 Scrapy class 的 parse() 方法，並且在 function 內部與plate_num_xlsx的每個迭代新值需要比較解析的值，正如我在 print 語句之后理解的那樣，它首先獲取所有值，然后僅分配它們分配的最后一個值調用 parse() 方法。 但是對於我的爬蟲到 function 正確我需要每次分配碰巧調用和使用 def parse() 中的值。 代碼如下；

import scrapy
from scrapy.crawler import CrawlerProcess
import pandas as pd

itemList=[]
class plateScraper(scrapy.Spider):
    name = 'scrapePlate'
    allowed_domains = ['dvlaregistrations.dvla.gov.uk']

    def start_requests(self):
        df=pd.read_excel('data.xlsx')
        columnA_values=df['PLATE']
        for row in columnA_values:
            global  plate_num_xlsx
            plate_num_xlsx=row
            print("+",plate_num_xlsx)
            base_url =f"https://dvlaregistrations.dvla.gov.uk/search/results.html?search={plate_num_xlsx}&action=index&pricefrom=0&priceto=&prefixmatches=&currentmatches=&limitprefix=&limitcurrent=&limitauction=&searched=true&openoption=&language=en&prefix2=Search&super=&super_pricefrom=&super_priceto="
            url=base_url
            yield scrapy.Request(url,callback=self.parse)

    def parse(self, response):

        for row in response.css('div.resultsstrip'):
            plate = row.css('a::text').get()
            price = row.css('p::text').get()
            a = plate.replace(" ", "").strip()
            print(plate_num_xlsx,a,a == plate_num_xlsx)
            if plate_num_xlsx==plate.replace(" ","").strip():
                item= {"plate": plate.strip(), "price": price.strip()}
                itemList.append(item)
                yield  item
            else:
                item = {"plate": plate_num_xlsx, "price": "-"}
                itemList.append(item)
                yield item

        with pd.ExcelWriter('output_res.xlsx', mode='r+',if_sheet_exists='overlay') as writer:
            df_output = pd.DataFrame(itemList)
            df_output.to_excel(writer, sheet_name='result', index=False, header=True)

process = CrawlerProcess()
process.crawl(plateScraper)
process.start()

Answer 1

由於它的異步運行時行為，以這種方式將全局變量與 scrapy 一起使用將不起作用。 或者，您可以將plate_num_xlsx變量作為回調關鍵字參數傳遞給請求 object 本身。

例如：

            plate_num_xlsx=row
            base_url =f"https://dvlaregistrations.dvla.gov.uk/search/results.html?search={plate_num_xlsx}&action=index&pricefrom=0&priceto=&prefixmatches=&currentmatches=&limitprefix=&limitcurrent=&limitauction=&searched=true&openoption=&language=en&prefix2=Search&super=&super_pricefrom=&super_priceto="
            url=base_url
            yield scrapy.Request(url,callback=self.parse, cb_kwargs={'plate_num_xlsx': plate_num_xlsx})



    def parse(self, response, plate_num_xlsx=None):
        for row in response.css('div.resultsstrip'):
            plate = row.css('a::text').get()
            price = row.css('p::text').get()
            ...

現在變量將作為參數包含在解析 function 中。