先看一个例子
class MyCustomStatsExtension(object):
"""
这个extension专门用来定期搜集一次stats
"""
def __init__(self, stats):
self.stats = stats
self.time = 60.0
@classmethod
def from_crawler(cls, crawler, *args, **kwargs):
instance = cls(crawler.stats)
crawler.signals.connect(instance.spider_opened, signal=signals.spider_opened)