Scrapy爬取图片： raise ValueError('Missing scheme in request url: %s' % self._url)

Scrapy爬取图片也很简单，有以下几点：
1.settings.py

BOT_NAME = 'tianmaoimg'

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


# Crawl responsibly by identifying yourself (and your website) on the user-agent
#USER_AGENT = 'tianmaoimg (+http://www.yourdomain.com)'
USER_AGENT = 'Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/56.0.2924.87 Safari/537.36'

# Obey robots.txt rules
ROBOTSTXT_OBEY = False

ITEM_PIPELINES = {'scrapy.pipelines.images.ImagesPipeline': 1}

IMAGES_URLS_FIELD='file_urls'
IMAGES_STORE = '/path/to/valid/images'

2.items.py

import scrapy


class TianmaoimgItem(scrapy.Item):
    # define the fields for your item here like:
    # name = scrapy.Field()

    #图片链接
    file_urls=scrapy.Field()

3.spider: getImgs.py 部分代码

   #图片链接
            try:
                file_urls=div.xpath('div[@class="productImg-wrap"]/a[@class="productImg"]/img/@src|'
                                   'div[@class="productImg-wrap"]/a[@class="productImg"]/img/@data-ks-lazyload').extract()
                #print file_urls[0]

####有错误
                item['file_urls']=file_urls[0] if 'http:' in file_urls[0] else ('http:'+file_urls[0])

            except Exception,e:
                print('error',e)

###########设置断点 ,跟踪代码的工具pdb,显示错误路径
                import pdb;pdb.set_trace()

            yield scrapy.Request(url=item['link_url'],meta={'item':item},callback=self.parse_item,dont_filter=True)

竟然报了一个很奇葩的错误

解决错误：
找了半天才从简书中知道，究其根源：
：在settings.py存储图片，其ITEM_PIPELINES = {‘scrapy.pipelines.images.ImagesPipeline’: 1}用到的是图片的url列表，而在Spider类中返回的是一个url字符串,所以ITEM_PIPELINES参数在执行循环获取url列表时，出现了只获取到了字符串的h，也就是上述的错误

所以改正：

item['file_urls']=[file_urls[0] if 'http:' in file_urls[0] else ('http:'+file_urls[0])]

ok