错误如下：
Traceback (most recent call last):
File
"C:/Users/HELLO/.PyCharm2018.2/config/scratches/spider_book.py", line 1, in
from .spider_dangdang import spider as dang
ModuleNotFoundError: No module named ‘main.spider_dangdang’; ‘main’ is not a package

京东和一号店的导入都没问题，淘宝因为不知道如何从网页源代码中提取出想要的数据所以还没做。
book代码：

from .spider_dangdang import spider as dangdang
from .spider_jd import spider as jd
from .spider_yhd import spider as yhd
from .spider_taobao import spider as taobao

def main(sn):
    book_list = []

    #当当网数据
    print('以下是当当')
    dangdang(sn,book_list)

    #京东网数据
    print('以下是京东')
    jd(sn,book_list)

    #一号店数据
    print('以下是一号店')
    yhd(sn,book_list)

    #淘宝网数据


    for book in book_list:
        print(book)
    print('=')*50

    #排序
    book_list = sorted(book_list,key=lambda item : item.price)
    for book in book_list:
        print(book)

if __name__ == '__main__':
    sn = input('请输入图书的ISBN编码：')
    main(sn)

以下是当当的代码

import requests
from lxml import html

def spider(sn,book_list=[]):
    url = 'http://search.dangdang.com/?key={sn}&act=input'.format(sn=sn)

    #获取html内容
    html_data = requests.get(url).text

    #获取xpath对象
    selector = html.fromstring(html_data)
    ul_list = selector.xpath('//div[@id="search_nature_rg"]/ul/li')
    #print(len(ul_list))
    #读取内容
    for li in ul_list:
        #标题
        title = li.xpath('a/@title')
        print(title[0])

        #链接
        link=li.xpath('a/@href')
        print(link[0])

        #价格
        price = li.xpath('p[@class="price"]/span[@class="search_now_price"]/text()')
        print(price[0].replace('¥',''))

        #店铺
        store = li.xpath('p[@class="search_shangjia"]/a/text()')
        store = '当当自营' if len(store)== 0 else store[0]
        print(store)
        print('-'*50)

        book_list.append({
            'title': title[0],
            'price': price[0].replace('¥', ''),
            'link': link[0],
            'store': store[0]
        })

if __name__ == '__main__':
    sn = 9787115428028
    spider(sn)