Jake Jake - 1 year ago 230
Python Question

How to add try exception in scrapy spider?

I build a simple crawler application by using urllib2 and beautifulsoup, now i am planning to change it into scrapy spider, but how i can handle errors while running crawler,
My current application have some code like this,

error_file = open('errors.txt','a')
finish_file = open('finishlink.txt','a')
#Code for process each links
#if sucessfully finished link store into 'finish.txt' file
except Exception as e:
#link write into 'errors.txt' file with error code

so when i am processing thousands of links, the successfully processed links will store into finish.txt and error's will be in errors.txt, so i can run links in errors later until successfully processed.
So how i can accomplish these in these code,

class DmozSpider(scrapy.Spider):
name = "dmoz"
allowed_domains = ["dmoz.org"]
start_urls = [

def parse(self, response):
filename = response.url.split("/")[-2]
with open('filename+'.txt', 'wb') as f:

Answer Source

You can create a spider middleware and override the process_spider_exception() method, saving the links in a file there.

A spider middleware is just a way for you to extend Scrapy's behavior. Here is a full example that you can modify as needed for your purpose:

from scrapy import signals

class SaveErrorsMiddleware(object):
    def __init__(self, crawler):
        crawler.signals.connect(self.close_spider, signals.spider_closed)
        crawler.signals.connect(self.open_spider, signals.spider_opened)

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

    def open_spider(self, spider):
        self.output_file = open('somefile.txt', 'a')

    def close_spider(self, spider):

    def process_spider_exception(self, response, exception, spider):
        self.output_file.write(response.url + '\n')

Put this in a module and set it up in settings.py:

    'myproject.middleware.SaveErrorsMiddleware': 1000,

This code will run together with your spider, triggering the open_spider(), close_spider(), process_spider_exception() methods when appropriated.

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