使用Scrapy下载图像时遇到问题

Question

当我尝试使用带有Scrapy的蜘蛛下载图像时，会出现以下错误。

File "C:\Python27\lib\site-packages\scrapy\http\request\__init__.py",
line 61, in _set_url
            raise ValueError('Missing scheme in request url: %s' % self._url)
        exceptions.ValueError: Missing scheme in request url: h

就我所能理解的而言，我好像在某个地方的url中少了一个“h”？但我一辈子也看不出在哪里。如果我不想下载图片，一切都正常。但是一旦我将适当的代码添加到下面的四个文件中，我就无法使任何东西正常工作。谁能帮我弄明白这个错误吗？

items.py

import scrapy

class ProductItem(scrapy.Item):
    model = scrapy.Field()
    shortdesc = scrapy.Field()
    desc = scrapy.Field()
    series = scrapy.Field()
    imageorig = scrapy.Field()
    image_urls = scrapy.Field()
    images = scrapy.Field()

设置.py

BOT_NAME = 'allenheath'

SPIDER_MODULES = ['allenheath.spiders']
NEWSPIDER_MODULE = 'allenheath.spiders'

ITEM_PIPELINES = {'scrapy.contrib.pipeline.images.ImagesPipeline': 1}

IMAGES_STORE = 'c:/allenheath/images'

pipelines.py

class AllenheathPipeline(object):
    def process_item(self, item, spider):
        return item

import scrapy
from scrapy.contrib.pipeline.images import ImagesPipeline
from scrapy.exceptions import DropItem

class MyImagesPipeline(ImagesPipeline):

    def get_media_requests(self, item, info):
        for image_url in item['image_urls']:
            yield scrapy.Request(image_url)

    def item_completed(self, results, item, info):
        image_paths = [x['path'] for ok, x in results if ok]
        if not image_paths:
            raise DropItem("Item contains no images")
        item['image_paths'] = image_paths
        return item

products.py（我的蜘蛛）

import scrapy

from allenheath.items import ProductItem
from scrapy.selector import Selector
from scrapy.http import HtmlResponse

class productsSpider(scrapy.Spider):
    name = "products"
    allowed_domains = ["http://www.allen-heath.com/"]
    start_urls = [
        "http://www.allen-heath.com/ahproducts/ilive-80/",
        "http://www.allen-heath.com/ahproducts/ilive-112/"
    ]

    def parse(self, response):
        for sel in response.xpath('/html'):
            item = ProductItem()
            item['model'] = sel.css('#prodsingleouter > div > div > h2::text').extract()
            item['shortdesc'] = sel.css('#prodsingleouter > div > div > h3::text').extract()
            item['desc'] = sel.css('#tab1 #productcontent').extract()
            item['series'] = sel.css('#pagestrip > div > div > a:nth-child(3)::text').extract()
            item['imageorig'] = sel.css('#prodsingleouter > div > div > h2::text').extract()
            item['image_urls'] = sel.css('#tab1 #productcontent img').extract()[0]
            item['image_urls'] = 'http://www.allen-heath.com' + item['image_urls']
            yield item

如有任何帮助，将不胜感激。

Answer 1

问题就在这里：

def get_media_requests(self, item, info):
    for image_url in item['image_urls']:
        yield scrapy.Request(image_url)

还有这里：

item['image_urls'] = sel.css('#tab1 #productcontent img').extract()[0]

您正在提取该字段并获取第一个元素。这意味着一旦您在管道中对它进行迭代,实际上就是对URL中的字符进行迭代,该URL以http开头--当第一个字母试图被处理时,就解释您看到的错误消息：

Missing scheme in request url: h

从该行中删除[0]。在此过程中，获取图像的src，而不是整个元素：

item['image_urls'] = sel.css('#tab1 #productcontent img').xpath('./@src').extract()

之后，如果图像url是相对的，您还应该更新下一行，以便将其转换为绝对的：

import urlparse  # put this at the top of the script
item['image_urls'] = [urlparse.urljoin(response.url, url) for url in item['image_urls']]

但如果src中的图像URL实际上是绝对的，则不需要最后这一部分，因此只需删除它即可。