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，并从该表中获取了几个字段.这些字段之一是url，我想对其进行探索以获取全新的字段.如何将已经创建的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?

如上面的代码所示，我能够将url(当前代码)中的字段或表中的字段保存(只需编写 yield item )但是我不能只将一个对象与所有字段放在一起.

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.

我已经尝试过了，但是很明显，这是行不通的.

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

这就是您要使用 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

还请注意，执行 sel = Selector(response)会浪费资源，并且与您之前所做的操作有所不同，因此我对其进行了更改.它会自动在 response 中映射为 response.selector ，它也具有 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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