1、新建一個擴充套件檔案，定義一個類，必須包含from_crawler方法：

from scrapy import signals


class MyExtend:

    def __init__(self, crawler):
        self.crawler = crawler
        # 給鉤子掛操作
        crawler.signals.connect(self.start, signals.engine_started)

    @classmethod
    def from_crawler(cls, crawler):
        
 
return cls(crawler)

    def start(self):
        # 自定義操作
        print('signals.engine_started')

2、設定settings

EXTENSIONS = {
    'day96.extensions.MyExtend': 300,
}

3、可以掛鉤子的地方

# 引擎開始執行的時候
engine_started = object()
# 引擎結束執行的時候
engine_stopped = object()

spider_opened = object()
spider_idle 
 
= object()
spider_closed = object()
spider_error = object()
request_scheduled = object()
request_dropped = object()
response_received = object()
response_downloaded = object()

# yield Item的時候
item_scraped = object()
# Item丟棄的時候
item_dropped = object()