scrapy 爬取小说保存的txt内容章节乱序，Pipeline中如何排序保存

[newuserpy]

如题，items中已经设置了num进行章节计数用，各章节按顺序绑定了num。

import scrapy
class MyItem(scrapy.Item):
    # define the fields for your item here like:
    # name = scrapy.Field()
    num = scrapy.Field() 
    desc = scrapy.Field()
    dname = scrapy.Field()       
    pass

piprlin如下，

import codecs
import os
import pdb

class MyPipeline(object):
    def process_item(self, item, spider):
        base_dir = os.getcwd()
        fiename = base_dir + '/小说.txt'
        with open(fiename, "a",encoding='utf-8') as f: 
            f.write(item['dname'] + "\n")
            f.write(item['desc'] +"\n\n") 
       return item

请问应该如何对item进行排序保存。

[newuserpy]

自己看了下书，已经会了。结贴。