将参数传递给回调函数 [英] Passing a argument to a callback function

问题描述

def parse(self, response):
    for sel in response.xpath('//tbody/tr'):
        item = HeroItem()
        item['hclass'] = response.request.url.split("/")[8].split('-')[-1]
        item['server'] = response.request.url.split('/')[2].split('.')[0]
        item['hardcore'] = len(response.request.url.split("/")[8].split('-')) == 3
        item['seasonal'] = response.request.url.split("/")[6] == 'season'
        item['rank'] = sel.xpath('td[@class="cell-Rank"]/text()').extract()[0].strip()
        item['battle_tag'] = sel.xpath('td[@class="cell-BattleTag"]//a/text()').extract()[1].strip()
        item['grift'] = sel.xpath('td[@class="cell-RiftLevel"]/text()').extract()[0].strip()
        item['time'] = sel.xpath('td[@class="cell-RiftTime"]/text()').extract()[0].strip()
        item['date'] = sel.xpath('td[@class="cell-RiftTime"]/text()').extract()[0].strip()
        url = 'https://' + item['server'] + '.battle.net/' + sel.xpath('td[@class="cell-BattleTag"]//a/@href').extract()[0].strip()

        yield Request(url, callback=self.parse_profile)

def parse_profile(self, response):
    sel = Selector(response)
    item = HeroItem()
    item['weapon'] = sel.xpath('//li[@class="slot-mainHand"]/a[@class="slot-link"]/@href').extract()[0].split('/')[4]
    return item

好吧，我正在主解析方法中抓取整个表，并且我从该表中提取了几个字段.其中一个字段是一个 url，我想探索它以获得一组全新的字段.如何将我已经创建的 ITEM 对象传递给回调函数，以便最终项目保留所有字段?

Well, I'm scraping a whole table in the main parse method and I have taken several fields from that table. One of these fields is an url and I want to explore it to get a whole new bunch of fields. How can I pass my already created ITEM object to the callback function so the final item keeps all the fields?

正如上面的代码所示，我可以保存 url 中的字段(目前的代码)或只保存表中的字段(只需编写 yield item)但我不能只产生一个对象，所有字段都放在一起.

As it is shown in the code above, I'm able to save the fields inside the url (code at the moment) or only the ones in the table (simply write yield item) but I can't yield only one object with all the fields together.

我已经试过了，但很明显，它不起作用.

I have tried this, but obviously, it doesn't work.

yield Request(url, callback=self.parse_profile(item))

def parse_profile(self, response, item):
    sel = Selector(response)
    item['weapon'] = sel.xpath('//li[@class="slot-mainHand"]/a[@class="slot-link"]/@href').extract()[0].split('/')[4]
    return item

推荐答案

这就是您使用 meta 关键字的目的.

This is what you'd use the meta Keyword for.

def parse(self, response):
    for sel in response.xpath('//tbody/tr'):
        item = HeroItem()
        # Item assignment here
        url = 'https://' + item['server'] + '.battle.net/' + sel.xpath('td[@class="cell-BattleTag"]//a/@href').extract()[0].strip()

        yield Request(url, callback=self.parse_profile, meta={'hero_item': item})

def parse_profile(self, response):
    item = response.meta.get('hero_item')
    item['weapon'] = response.xpath('//li[@class="slot-mainHand"]/a[@class="slot-link"]/@href').extract()[0].split('/')[4]
    yield item

还要注意，做 sel = Selector(response) 是一种资源浪费，和你之前做的不同，所以我改变了它.它在response中自动映射为response.selector，也有response.xpath的便捷快捷方式.

Also note, doing sel = Selector(response) is a waste of resources and differs from what you did earlier, so I changed it. It's automatically mapped in the response as response.selector, which also has the convenience shortcut of response.xpath.

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