为scrapy中spider的开始url列表中给出的每个url提供单独的输出文件

Question

我想为我在spider的start_url中设置的每个url创建单独的输出文件，或者以某种方式将输出文件拆分为start url。

以下是我的爬行器的起始URL

start_urls = ['http://www.dmoz.org/Arts/', 'http://www.dmoz.org/Business/', 'http://www.dmoz.org/Computers/']

我想创建单独的输出文件，如

Arts.xml
Business.xml
Computers.xml

我不知道该怎么做。我想通过在item pipeline类的spider_opened方法中实现如下内容来实现这一点，

import re
from scrapy import signals
from scrapy.contrib.exporter import XmlItemExporter

class CleanDataPipeline(object):
    def __init__(self):
        self.cnt = 0
        self.filename = ''

    @classmethod
    def from_crawler(cls, crawler):
        pipeline = cls()
        crawler.signals.connect(pipeline.spider_opened, signals.spider_opened)
        crawler.signals.connect(pipeline.spider_closed, signals.spider_closed)
        return pipeline

    def spider_opened(self, spider):
        referer_url = response.request.headers.get('referer', None)
        if referer_url in spider.start_urls:
            catname = re.search(r'/(.*)$', referer_url, re.I)
            self.filename = catname.group(1)

        file = open('output/' + str(self.cnt) + '_' + self.filename + '.xml', 'w+b')
        self.exporter = XmlItemExporter(file)
        self.exporter.start_exporting()

    def spider_closed(self, spider):
        self.exporter.finish_exporting()
        #file.close()

    def process_item(self, item, spider):
        self.cnt = self.cnt + 1
        self.spider_closed(spider)
        self.spider_opened(spider)
        self.exporter.export_item(item)
        return item

在这里，我试图找到开始url列表中每个已删除项目的引用url。如果在start_url中找到referer url，则将使用该referer url创建文件名。但问题是如何访问spider_opened（）方法中的响应对象。如果我可以在那里访问它，我可以基于它创建文件。

找到执行此操作的html" target="_blank">方法有什么帮助吗？提前谢谢！

[编辑]

通过如下更改我的管道代码来解决我的问题。

import re
from scrapy import signals
from scrapy.contrib.exporter import XmlItemExporter

class CleanDataPipeline(object):
    def __init__(self):
        self.filename = ''
        self.exporters = {}

    @classmethod
    def from_crawler(cls, crawler):
        pipeline = cls()
        crawler.signals.connect(pipeline.spider_opened, signals.spider_opened)
        crawler.signals.connect(pipeline.spider_closed, signals.spider_closed)
        return pipeline

    def spider_opened(self, spider, fileName = 'default.xml'):
        self.filename = fileName
        file = open('output/' + self.filename, 'w+b')
        exporter = XmlItemExporter(file)
        exporter.start_exporting()
        self.exporters[fileName] = exporter

    def spider_closed(self, spider):
        for exporter in self.exporters.itervalues(): 
            exporter.finish_exporting()

    def process_item(self, item, spider):
        fname = 'default'
        catname = re.search(r'http://www.dmoz.org/(.*?)/', str(item['start_url']), re.I)
        if catname:
            fname = catname.group(1)
        self.curFileName = fname + '.xml'

        if self.filename == 'default.xml':
            if os.path.isfile('output/' + self.filename):
                os.rename('output/' + self.filename, 'output/' + self.curFileName)
            exporter = self.exporters['default.xml']
            del self.exporters['default.xml']
            self.exporters[self.curFileName] = exporter
            self.filename = self.curFileName

        if self.filename != self.curFileName and not self.exporters.get(self.curFileName):
            self.spider_opened(spider, self.curFileName)

        self.exporters[self.curFileName].export_item(item)
        return item

还实现了spider中的make\u requests\u from\u url，以设置每个项目的开始\u url。

def make_requests_from_url(self, url):
    request = Request(url, dont_filter=True)
    request.meta['start_url'] = url
    return request

Answer 1

以下是我如何在没有设置项目类别的情况下为我的项目做的：

按如下方式从命令行传递参数：

scrapy crawl reviews_spider -a brand_name=apple

接收参数并在my_spider.py中设置为spider args

def __init__(self, brand_name, *args, **kwargs):
    self.brand_name = brand_name
    super(ReviewsSpider, self).__init__(*args, **kwargs)

    # i am reading start_urls from an external file depending on the passed argument
    with open('make_urls.json') as f:
        self.start_urls = json.loads(f.read())[self.brand_name]

在pipelines.py中：

class ReviewSummaryItemPipeline(object):
    @classmethod
    def from_crawler(cls, crawler):
        pipeline = cls()
        crawler.signals.connect(pipeline.spider_opened, signals.spider_opened)
        crawler.signals.connect(pipeline.spider_closed, signals.spider_closed)
        return pipeline

    def spider_opened(self, spider):
        # change the output file name based on argument
        self.file = open(f'reviews_summary_{spider.brand_name}.csv', 'w+b')
        self.exporter = CsvItemExporter(self.file)
        self.exporter.start_exporting()

    def spider_closed(self, spider):
        self.exporter.finish_exporting()
        self.file.close()

    def process_item(self, item, spider):
        self.exporter.export_item(item)
        return item

Answer 2

只要不将其存储在项目本身中，就无法真正了解起始url。以下解决方案适用于您：

>

一旦您决定将元素传递到管道，请填写response.meta['start\u url']

希望能有帮助。以下链接可能会有所帮助：

http://doc.scrapy.org/en/latest/topics/spiders.html#scrapy.spider.Spider.make_requests_from_url

http://doc.scrapy.org/en/latest/topics/request-response.html?highlight=meta#passing-additional-data-to-callback-functions

Answer 3

我将实施一种更明确的方法（未经测试）：

>

CATEGORIES = ['Arts', 'Business', 'Computers']

根据设置定义您的start_urls

start_urls = ['http://www.dmoz.org/%s' % category for category in settings.CATEGORIES]

添加类别字段到项目类

在蜘蛛的解析方法中，根据当前的response.url设置类别字段，例如：

def parse(self, response):
     ...
     item['category'] = next(category for category in settings.CATEGORIES if category in response.url)
     ...

在管道中，打开所有类别的导出器，并根据项['category']选择要使用的导出器：

def spider_opened(self, spider):
    ...
    self.exporters = {}
    for category in settings.CATEGORIES:
        file = open('output/%s.xml' % category, 'w+b')
        exporter = XmlItemExporter(file)
        exporter.start_exporting()
        self.exporters[category] = exporter

def spider_closed(self, spider):
    for exporter in self.exporters.itervalues(): 
        exporter.finish_exporting()

def process_item(self, item, spider):
    self.exporters[item['category']].export_item(item)
    return item

您可能需要对其进行一些调整，以使其正常工作，但我希望您已经有了想法-将类别存储在正在处理的项中。根据项目类别值选择要导出到的文件。

希望这有所帮助。