抓取爬虫在作为脚本运行时会忽略`DOWNLOADER_MIDDLEWARES`

Question

我想使用刮痕从几个不同的站点获取数据，并对这些数据进行一些分析。由于爬虫和分析数据的代码都与同一个项目有关，所以我想将所有内容存储在同一个Git存储库中。我创建了一个Github的最小可重现性实例。

该项目的结构如下：

./crawlers
./crawlers/__init__.py
./crawlers/myproject
./crawlers/myproject/__init__.py
./crawlers/myproject/myproject
./crawlers/myproject/myproject/__init__.py
./crawlers/myproject/myproject/items.py
./crawlers/myproject/myproject/pipelines.py
./crawlers/myproject/myproject/settings.py
./crawlers/myproject/myproject/spiders
./crawlers/myproject/myproject/spiders/__init__.py
./crawlers/myproject/myproject/spiders/example.py
./crawlers/myproject/scrapy.cfg
./scrapyScript.py

在./crawlers/myproject文件夹中，我可以通过键入以下命令来执行爬行器：

scrapy crawl example

爬虫使用了一些下载中间件，特别是阿莱克斯氏症优秀的刮-假-用户代理。来自settings.py

DOWNLOADER_MIDDLEWARES = {
    'scrapy.contrib.downloadermiddleware.useragent.UserAgentMiddleware': None,
    'scrapy_fake_useragent.middleware.RandomUserAgentMiddleware': 400,
}

当使用scrapy crawl ...执行时，useragent看起来像一个真正的浏览器。下面是来自Here服务器的一个示例记录：

24.8.42.44 - - [16/Jun/2015:05:07:59 +0000] "GET / HTTP/1.1" 200 27161 "-" "Mozilla/5.0 (Windows NT 6.3; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/37.0.2049.0 Safari/537.36"

从文档的角度来看，可以从脚本中执行相当于scrapy crawl ...的操作。基于文档的scrapyScript.py文件如下所示：

from twisted.internet import reactor
from scrapy.crawler import Crawler
from scrapy import log, signals

from scrapy.utils.project import get_project_settings
from crawlers.myproject.myproject.spiders.example import ExampleSpider

spider = ExampleSpider()
settings = get_project_settings()

crawler = Crawler(settings)
crawler.signals.connect(reactor.stop, signal=signals.spider_closed)
crawler.configure()
crawler.crawl(spider)

crawler.start()
log.start()
reactor.run()

当我执行这个脚本时，我可以看到爬虫发出页面请求。不幸的是，它忽略了DOWNLOADER_MIDDLEWARES。例如，用户代理不再被欺骗：

24.8.42.44 - - [16/Jun/2015:05:32:04 +0000] "GET / HTTP/1.1" 200 27161 "-" "Scrapy/0.24.6 (+http://scrapy.org)"

不知何故，当从脚本执行爬虫时，它似乎忽略了settings.py中的设置。

你能看出我做错了什么吗？

Answer 1

为了让get_project_settings()找到所需的settings.py，设置环境变量

import os
import sys

# ...

sys.path.append(os.path.join(os.path.curdir, "crawlers/myproject"))
os.environ['SCRAPY_SETTINGS_MODULE'] = 'myproject.settings'

settings = get_project_settings()

注意，由于运行脚本的位置，需要将myproject添加到sys.path中。或者，将scrapyScript.py移动到myproject目录下。