pipelines中重命名scrapy下载的图片

from __future__ import unicode_literals
import sys

from scrapy.pipelines.images import ImagesPipeline
from scrapy.exceptions import DropItem
from scrapy.http import Request
import os
reload(sys)
sys.setdefaultencoding('utf-8')
class TetePipeline(ImagesPipeline):
    def get_media_requests(self, item, info):
        for image_url in item['image_urls']:
            yield Request(image_url)

    def item_completed(self, results, item, info):
        item['image'] = []
        image_paths = [x['path'] for ok, x in results if ok]
        if not image_paths:
            raise DropItem('Items contains no images')
        item['image_paths'] = image_paths
        for i in item['image_paths']:
            item['image'].append(item['image_titles']+i[-8:]) 
        item['image_paths'] = item['image']
        return item

想改变scrapy下载的图片的名称，使用自定义名字，打算使用file_path,但是file_path改动太大。
这个可以下载图片，但是图片名称是是图像url的 SHA1 hash，为什么呢？

---

class MyImagePipelines(ImagesPipeline):

    def get_media_requests(self, item, info):
       for image_url in item['image_urls']:
           yield scrapy.Request(image_url,meta={'item': item})
    def item_completed(self, results, item, info):
        image_paths = [x['path'] for ok, x in results if ok]
        if not image_paths:
            raise FengniaomoteItem("Item contains no images")
        return item
    def file_path(self, request, response=None, info=None):
        item = request.meta['item']
        image_guid = request.url.split('/')[-1]

        filename = u'full/{0[mote_id]}/{1}'.format(item, image_guid)
        return filename

你看我的，最下面的filename就是更改了图片的名字以及存放的目录