Question

我无法在parse方法中更改spider设置。但绝对必须是一种方式。

例如：

class SomeSpider(BaseSpider):
    name = 'mySpider'
    allowed_domains = ['example.com']
    start_urls = ['http://example.com']
    settings.overrides['ITEM_PIPELINES'] = ['myproject.pipelines.FirstPipeline']
    print settings['ITEM_PIPELINES'][0]
    #printed 'myproject.pipelines.FirstPipeline'
    def parse(self, response):
        #...some code
        settings.overrides['ITEM_PIPELINES'] = ['myproject.pipelines.SecondPipeline']
        print settings['ITEM_PIPELINES'][0]
        # printed 'myproject.pipelines.SecondPipeline'
        item = Myitem()
        item['mame'] = 'Name for SecondPipeline'

但是！项目将由FirstPipeline处理。新的ITEM_PIPELINES参数不起作用。如何在开始抓取后更改设置？提前谢谢！

Answer 1

如果您希望不同的蜘蛛拥有不同的管道，您可以为蜘蛛设置管道列表属性，该属性定义该蜘蛛的管道。比管道检查存在：

class MyPipeline(object):

    def process_item(self, item, spider):
        if self.__class__.__name__ not in getattr(spider, 'pipelines',[]):
            return item
        ...
        return item

class MySpider(CrawlSpider):
    pipelines = set([
        'MyPipeline',
        'MyPipeline3',
    ])

如果您希望不同的管道可以处理不同的项目，您可以这样做：

    class MyPipeline2(object):
        def process_item(self, item, spider):
            if isinstance(item, MyItem):
                ...
                return item
            return item

Answer 2

基于此信息丰富的issue#4196与telnet console的结合，甚至可以在执行后执行。

在启动1234命令时将telnet客户端连接到 port （例如scrapy crawl）和 password 并记录以下内容修改当前运行的downloader的Python语句：

$ telnet  127.0.0.1  6023  # Read the actual port from logs.
Trying 127.0.0.1...
Connected to 127.0.0.1.
Escape character is '^]'.
Username: scrapy
Password: <copy-from-logs>

>>> engine.downloader.total_concurrency
8
>>> engine.downloader.total_concurrency = 32
>>> est()
Execution engine status

time()-engine.start_time                        : 14226.62803554535
engine.has_capacity()                           : False
len(engine.downloader.active)                   : 28
engine.scraper.is_idle()                        : False
engine.spider.name                              : <foo>
engine.spider_is_idle(engine.spider)            : False
engine.slot.closing                             : False
len(engine.slot.inprogress)                     : 32
len(engine.slot.scheduler.dqs or [])            : 531
len(engine.slot.scheduler.mqs)                  : 0
len(engine.scraper.slot.queue)                  : 0
len(engine.scraper.slot.active)                 : 0
engine.scraper.slot.active_size                 : 0
engine.scraper.slot.itemproc_size               : 0
engine.scraper.slot.needs_backout()             : False

Scrapy。如何在开始爬行后更改蜘蛛设置？

2 个答案: