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python - 管道文件中存在问题，因为它没有获取书名。而是为每次爬网保存一个带有 None.jpg 的随机图像

问题描述

items.py 文件。因为我知道 image_urls 和 images 字段。它没有造成任何问题。

import scrapy
from scrapy.loader.processors import TakeFirst

class BooksToScrapeItem(scrapy.Item):
    image_urls = scrapy.Field()
    images = scrapy.Field()
    book_name = scrapy.Field(
        output_processor = TakeFirst()
    )

管道.py 文件。我认为 get_media_request 方法一定有问题，因为它没有从项目文件中获取 book_name

from scrapy.pipelines.images import ImagesPipeline
from scrapy import Request


class BooksToScrapeImagePipeline(ImagesPipeline):

    def get_media_requests(self, item, info):
        return [Request(x,meta={'bookname': item.get('book_name')}) for x in item.get(self.images_urls_field, [])] #i think that the problem is in this line

    def file_path(self, request, response=None, info=None):

        return 'full/%s.jpg' % (request.meta['bookname'])

我用于抓取的蜘蛛文件。当我没有自定义管道文件时它工作。

import scrapy
from scrapy.loader import ItemLoader
from books_to_scrape.items import BooksToScrapeItem

class ImgscrapeSpider(scrapy.Spider):
    name = 'imgscrape'
    allowed_domains = ['books.toscrape.com']
    start_urls = ['http://books.toscrape.com']

    def parse(self, response):
        for article in response.xpath("//article[@class='product_pod']"):
            loader = ItemLoader(item=BooksToScrapeItem(),selector=article)
            relative_url = article.xpath(".//div/a/img[@class='thumbnail']/@src").extract_first()
            abs_url = response.urljoin(relative_url)
            loader.add_value('image_urls',abs_url)
            loader.add_xpath('book_name',".//article[@class='product_pod']/h3/a/text()") 
            yield loader.load_item()

标签： pythonscrapyfilenames

解决方案

您的问题出在相对 xpath 中

loader.add_xpath('book_name', ".//article[@class='product_pod']/h3/a/text()")

加载器xpath("//article[@class='product_pod']")用作选择器

   for article in response.xpath("//article[@class='product_pod']"):
        loader = ItemLoader(item=BooksToScrapeItem(), selector=article)

所以所有相对的 xpath 都是相对的，它们在 xpath 中"//article[@class='product_pod']"不需要。"//article[@class='product_pod']"

使用相对 xpath".//article[@class='product_pod']/h3/a/text()"它找不到标题，因此book_name对于所有项目和用作None标题的所有项目都是空的 - 它对所有图像使用相同的名称None.jpg。

它一定要是

loader.add_xpath('book_name', ".//h3/a/text()")  # title with `...`

顺便说一句： text()没有完整的标题，但带有.... 要获得完整的标题，您必须获得属性title=

loader.add_xpath('book_name', ".//h3/a/@title")  # full title

我在一个文件中创建了包含所有代码的版本以在不创建项目的情况下运行它。

每个人都可以将其复制到单个文件并运行以进行测试。

import scrapy
from scrapy.loader.processors import TakeFirst

class BooksToScrapeItem(scrapy.Item):
    image_urls = scrapy.Field()
    images = scrapy.Field()
    book_name = scrapy.Field(
        output_processor = TakeFirst()
    )

from scrapy import Request
from scrapy.pipelines.images import ImagesPipeline

class BooksToScrapeImagePipeline(ImagesPipeline):

    def get_media_requests(self, item, info):
        return [Request(x, meta={'bookname': item.get('book_name')}) for x in item.get(self.images_urls_field, [])] #i think that the problem is in this line

    def file_path(self, request, response=None, info=None):
        return 'full/%s.jpg' % request.meta['bookname']

from scrapy.loader import ItemLoader

class ImgscrapeSpider(scrapy.Spider):
    name = 'imgscrape'
    allowed_domains = ['books.toscrape.com']
    start_urls = ['http://books.toscrape.com']

    def parse(self, response):
        for article in response.xpath("//article[@class='product_pod']"):

            loader = ItemLoader(item=BooksToScrapeItem(),selector=article)

            relative_url = article.xpath(".//div/a/img[@class='thumbnail']/@src").extract_first()
            abs_url = response.urljoin(relative_url)

            loader.add_value('image_urls', abs_url)
            #loader.add_xpath('book_name',".//article[@class='product_pod']/h3/a/text()")  # wrong relative xpath 
            #loader.add_xpath('book_name', ".//h3/a/text()")  # only partial title
            loader.add_xpath('book_name', ".//h3/a/@title")  # full title

            yield loader.load_item() 

# -----------------------------------------------------------------------------

from scrapy.crawler import CrawlerProcess

c = CrawlerProcess({
    'USER_AGENT': 'Mozilla/5.0',

    # save in file CSV, JSON or XML
    'FEED_FORMAT': 'csv',     # csv, json, xml
    'FEED_URI': 'output.csv', #

    # download images to `IMAGES_STORE/full` (standard folder) and convert to JPG (even if it is already JPG)
    # it needs `yield {'image_urls': [url]}` in `parse()` and both ITEM_PIPELINES and IMAGES_STORE to work

    'ITEM_PIPELINES': {'__main__.BooksToScrapeImagePipeline': 1},            # used Pipeline create in current file (needs __main___)
    'IMAGES_STORE': '.',                   # this folder has to exist before downloading

})
c.crawl(ImgscrapeSpider)
c.start()

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