如何在Python中通过__init__设置class变量？

Question

我正在尝试在启动 scrapy 爬虫 (Python 3.7) 时从命令行更改设置。因此，我添加了一个 init 方法，但我不知道如何从 init[=25= 中更改 class 变量“延迟” ] 方法。

最小示例：

class testSpider(CrawlSpider):

    custom_settings = {
        'DOWNLOAD_DELAY': 10,  # default value
    }

    """ get arguments passed over CLI
        scrapyd usage: -d arg1=val1
        scrapy  usage: -a arg1=val1
    """
    def __init__(self, *args, **kwargs):
        super(testSpider, self).__init__(*args, **kwargs)

        self.delay = kwargs.get('delay')

        if self.delay:
            testSpider.custom_settings['DOWNLOAD_DELAY'] = self.delay
            print('init:', testSpider.custom_settings['DOWNLOAD_DELAY'])

    print(custom_settings['DOWNLOAD_DELAY'])

不幸的是，这不会更改设置：

scrapy crawl test -a delay=5
10
init: 5

如何更改class变量？

Answer 1

I am trying to change setting from command line while starting a scrapy crawler (Python 3.7). Therefore I am adding a init method...
...
scrapy crawl test -a delay=5

1. 根据scrapy docs. (Settings/Command line options section) 需要使用 -s 参数来更新设置
   scrapy crawl test -s DOWNLOAD_DELAY=5

2. 无法通过init或其他方法在爬虫代码运行时更新设置（详情见githubUpdate spider settings during runtime #4196