Scrapy 管道加载但不起作用

Question

我有一个 Scrapy 项目，它加载管道但不向它们传递项目。感谢您的帮助。

蜘蛛的精简版:

#imports
class MySpider(CrawlSpider):
  #RULES AND STUFF 

  def parse_item(self, response):
    '''Takes HTML response and turns it into an item ready for database.  I hope.
    '''
    #A LOT OF CODE
    return item

此时打印出项目会产生预期的结果，settings.py 非常简单:

ITEM_PIPELINES = [
  'mySpider.pipelines.MySpiderPipeline',
  'mySpider.pipelines.PipeCleaner',
  'mySpider.pipelines.DBWriter',
]

管道似乎是正确的(没有导入):

class MySpiderPipeline(object):
  def process_item(self, item, spider):
    print 'PIPELINE: got ', item['name']
    return item

class DBWriter(object):
  """Writes each item to a DB.  I hope.
  """
  def __init__(self):
    self.dbpool = adbapi.ConnectionPool('MySQLdb'
                                        , host=settings['HOST']
                                        , port=int(settings['PORT'])
                                        , user=settings['USER']
                                        , passwd=settings['PASS']
                                        , db=settings['BASE']
                                        , cursorclass=MySQLdb.cursors.DictCursor
                                        , charset='utf8'
                                        , use_unicode=True
                                        )
    print('init DBWriter')

  def process_item(self, item, spider):
    print 'DBWriter process_item'
    query = self.dbpool.runInteraction(self._insert, item)
    query.addErrback(self.handle_error)
    return item

  def _insert(self, tx, item):
    print 'DBWriter _insert'
    # A LOT OF UNRELATED CODE HERE
    return item

class PipeCleaner(object):
  def __init__(self):
    print 'Cleaning these pipes.'

  def process_item(self, item, spider):
    print item['name'], ' is cleeeeaaaaannn!!'
    return item

当我运行 spider 时，我在启动时得到了这个输出:

Cleaning these pipes.
init DBWriter
2012-10-23 15:30:04-0400 [scrapy] DEBUG: Enabled item pipelines: MySpiderPipeline, PipeCleaner, DBWriter

不像它们的 init 子句在爬虫启动时打印到屏幕上，process_item 方法不打印(或处理)任何东西。我祈祷我忘记了一些非常简单的事情。

Answer 1

2012-10-23 15:30:04-0400 [scrapy] DEBUG: Enabled item pipelines: MySpiderPipeline, PipeCleaner, DBWriter

此行表明您的管道正在初始化并且它们正常。

问题是你的爬虫类，

class MySpider(CrawlSpider):
  #RULES AND STUFF 

  def parse_item(self, response):
    '''Takes HTML response and turns it into an item ready for database.  I hope.
    '''
    #A LOT OF CODE
    # before returning item , print it 
    return item

我认为你应该打印一个项目，然后从 MySpider 返回它。