前言

这是 Scrapy 系列学习文章之一，本章主要介绍 Exceptions 的相关的内容；

本文为作者的原创作品，转载需注明出处；

内置 Exceptions 一览

DropItem

1	exception scrapy.exceptions.DropItem

The exception that must be raised by item pipeline stages to stop processing an Item. For more information see 爬虫 Scrapy 学习系列之九：Item Pipeline">Item Pipeline；

在 Item Pipeline 执行过程中，如果需要终止对某个 Item 的执行，那么此异常是必须被抛出的；

CloseSpider

1	exception scrapy.exceptions.CloseSpider(reason='cancelled')

在 spider 的回调方法中抛出，目的是终止当前的 spider 继续执行；

Parameters: reason (str) – the reason for closing

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def parse_page(self, response):
    if 'Bandwidth exceeded' in response.body:
        raise CloseSpider('bandwidth_exceeded')

IgnoreRequest

1	exception scrapy.exceptions.IgnoreRequest

This exception can be raised by the Scheduler or any downloader middleware to indicate that the request should be ignored.

NotConfigured

1	exception scrapy.exceptions.NotConfigured

This exception can be raised by some components to indicate that they will remain disabled. Those components include:

通过该异常表示某些 components 当前不可用

Extensions
Item pipelines
Downloader middlewares
Spider middlewares

The exception must be raised in the component’s __init__ method.

NotSupported

1	exception scrapy.exceptions.NotSupported

This exception is raised to indicate an unsupported feature.