extensions.py 文件源码

def from_crawler(cls, crawler):
        instance = cls(crawler.stats)
        crawler.signals.connect(instance.item_dropped, 
                                signal=signals.item_dropped)
        crawler.signals.connect(instance.item_scraped, 
                                signal=signals.item_scraped)

        crawler.signals.connect(instance.response_received, 
                                signal=signals.response_received)
        crawler.signals.connect(instance.response_downloaded, 
                                signal=signals.response_downloaded)
        return instance