（Python）在一个模块中从__init__导入参数以在另一个模块中使用？

Question

I'm really new to Python and have been using it in conjunction with Scrapy for making some web crawlers. When running a spider from the terminal I can use "-a NAME=VALUE" to set arguments, which is especially useful for directing it to different domains. I'm trying use the "domain" argument as a variable in another module but got stuck. Here's a portion of the module I'm trying to import the argument from:

class Spider(spiders.CrawlSpider):
    name = 'changelog'
    rules = (spiders.Rule(SgmlLinkExtractor(), callback='parse_item', follow=True),)

    def __init__(self, domain='WHAT_IM_TRYING_TO_FIND', *args, **kwargs):
        super(Spider, self).__init__(*args, **kwargs)
        self.domain = domain
        self.allowed_domains = [domain]
        self.start_urls = [
            'http://%s/' % domain,
            'http://%s/index.html' % domain,
            'http://%s/index.php' % domain,
        ]

In a separate module, trying things like

from MyModule import Spider

variable = Spider.domain

or

variable = __import __ ('MyModule').Spider.domain

gives me

Class 'Spider' has no 'domain' member

Any guidance will be greatly appreciated!

Scrapy's file structure looks like this:

myproject/
__init __.py
items.py
pipelines.py
settings.py
spiders/
    __init __.py
    spider.py

Answer 1

domain is an attribute of instances of Spider, not of the Spider class. You can only access domain if you have an instance of Spider created somewhere.