Python xpath有一个空值，它会把列表弄乱

我正在使用下面的代码从网页上抓取姓名、地址和汽车数量

但是，汽车数量经常有一个空值。在下面的示例中，假设第八家经销商返回的汽车数量为空，因此返回的列表如下所示：

名称=a、b、c、d、e、f、g、h、i、j

地址=aa、bb、cc、dd、ee、ff、gg、hh、ii、jj

cars=1,2,3,4,5,6,7,9,10

如果地址aa处的经销商a有1辆车，地址bb处的经销商b有2辆车等，但由于地址hh处的经销商h有一个空值，因此跳过该代码，相反，该代码认为经销商h有9辆车，因此经销商i和地址ii有10辆车，因此地址jj处的经销商j被遗漏，因为车辆列表已用完

因此，如果代码返回cars的空值，如何用0替换该值？因此，在上面的示例中，经销商h和地址hh将有0辆车，因此地址ii处的经销商i有9辆车，地址jj处的经销商j有10辆车

import scrapy

from autotrader.items import AutotraderItem

class AutotraderSpider(scrapy.Spider):
    name = "autotrader"
    allowed_domains = ["autotrader.co.uk"]

    start_urls = ["https://www.autotrader.co.uk/car-dealers/search?advertising-location=at_cars&postcode=m43aq&radius=1500&forSale=on&toOrder=on&sort=with-retailer-reviews&page=822"]

    def parse(self, response):
        for sel in response.xpath('//ul[@class="dealerList__container"]'):
            names = sel.xpath('.//*[@itemprop="legalName"]/text() ').extract()
            names = [name.strip() for name in names]
            addresses = sel.xpath('.//li/article/a/div/p[@itemprop="address"]/text()').extract()
            addresses = [address.strip() for address in addresses]
            carss = sel.xpath('.//li/article/a/div/p[@class="dealerList__itemCount"]/span/text()').extract() 
            carss = [cars.strip() for cars in carss]
            result = zip(names, addresses, carss)
            for name, address, cars in result:
                item = AutotraderItem()
                item['name'] = name
                item['address'] = address
                item['cars'] = cars
                yield item

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您的选择器循环有点混乱

在这里，您可以循环浏览未排序的列表，其中每个年龄只有一个列表：

for sel in response.xpath('//ul[@class="dealerList__container"]'):

您需要的是循环浏览所有列表项：

for sel in response.xpath('//li[@class="dealerList__itemContainer"]'):

如果以这种方式循环，则可以获得每个列表项的名称、地址：

for sel in response.xpath('//li[@class="dealerList__itemContainer"]'):
    names = sel.xpath('.//*[@itemprop="legalName"]/text() ').extract()
    names = [name.strip() for name in names]
    addresses = sel.xpath('.//article/a/div/p[@itemprop="address"]/text()').extract()
    addresses = [address.strip() for address in addresses]
    carss = sel.xpath('.//article/a/div/p[@class="dealerList__itemCount"]/span/text()').extract() 
    carss = [cars.strip() for cars in carss]
    item = AutotraderItem()
    item['name'] = name
    item['address'] = address
    item['cars'] = cars
    yield item

---

试试这个来得到结果。您可以在scrapy项目中使用

xpaths

，如下所示：

class AutotraderSpider(scrapy.Spider):
    name = "autotrader"
    allowed_domains = ["autotrader.co.uk"]

    start_urls = ["https://www.autotrader.co.uk/car-dealers/search?advertising-location=at_cars&postcode=m43aq&radius=1500&forSale=on&toOrder=on&sort=with-retailer-reviews&page=822"]

    def parse(self, response):
        for items in response.xpath("//article[@class='dealerList__item']"):
            name = items.xpath(".//span[@itemprop='legalName']/text()").extract_first()
            address = ' '.join([' '.join(item.split()) for item in items.xpath(".//p[@class='dealerList__itemAddress']/text()").extract()])
            cars = items.xpath(".//span[@class='dealerList__itemCountNumber']/text()").extract_first()
            yield {"Name":name,"Address":address,"Cars":cars}

部分输出：

Midland Motors Leicester Street, Burton-On-Trent, Staffordshire DE14 3BA 2
Ns Cars 69 Eldon Street, Burton-On-Trent, Staffordshire DE15 0LT 1
RS Sales Nottingham Ltd Unit 1 TRINITY PARK, RANDALL PARK WAY, Retford, Nottinghamshire DN22 7WF 1
Adc Ltd Unit 3 HUCKNALL LANE, Nottingham, Nottinghamshire NG6 8AJ 5

---

最简单的答案是重新组织代码，这样就不用进行三次单独的xpath查询并尝试将结果压缩在一起，而是进行一次顶级查询以获取组，然后针对每个组，使用xpath从组中获取三个子字段。这很有魅力，谢谢。值得注意的是，对于阅读上述代码的人来说，解决方案是

for sel in response.xpath（'//li[@class=“dealerList\uu itemContainer”]）：

带有变量名称、carrs等的示例代码需要调整，方法是将名称更改为name etc，并去掉其中包含名称.strip（）等的某些行。