scrapy的pipeline是一個非常重要的模塊，主要作用是將return的items寫入到數據庫、文件等持久化模塊，下面我們就簡單的了解一下pipelines的用法。

案例一：

items池

class ZhihuuserItem(scrapy.Item):
    # define the fields for your item here like:
    # name = scrapy.Field()
    id = scrapy.Field()
    name = scrapy.Field()
    avatar_url = scrapy.Field()
    headline 
 
= scrapy.Field()
    description = scrapy.Field()
    url = scrapy.Field()
    url_token = scrapy.Field()
    gender = scrapy.Field()
    cover_url = scrapy.Field()
    type = scrapy.Field()
    badge = scrapy.Field()

    answer_count = scrapy.Field()
    articles_count = scrapy.Field()
    commercial_question 
 
= scrapy.Field()
    favorite_count = scrapy.Field()
    favorited_count = scrapy.Field()
    follower_count = scrapy.Field()
    following_columns_count = scrapy.Field()
    following_count = scrapy.Field()
    pins_count = scrapy.Field()
    question_count = scrapy.Field()
    thank_from_count = scrapy.Field()
    thank_to_count 
 
= scrapy.Field()
    thanked_count = scrapy.Field()
    vote_from_count = scrapy.Field()
    vote_to_count = scrapy.Field()
    voteup_count = scrapy.Field()
    following_favlists_count = scrapy.Field()
    following_question_count = scrapy.Field()
    following_topic_count = scrapy.Field()
    marked_answers_count = scrapy.Field()
    mutual_followees_count = scrapy.Field()
    participated_live_count = scrapy.Field()

    locations = scrapy.Field()
    educations = scrapy.Field()
    employments = scrapy.Field()

寫入MongoDB數據庫的基本配置

#配置MongoDB數據庫的連接信息
MONGO_URL = ‘172.16.5.239‘
MONGO_PORT = 27017
MONGO_DB = ‘zhihuuser‘

#參數等於False，就等於告訴你這個網站你想取什麽就取什麽，不會讀取每個網站的根目錄下的禁止爬取列表(例如：www.baidu.com/robots.txt）
ROBOTSTXT_OBEY = False


執行pipelines下的寫入操作
ITEM_PIPELINES = {
   ‘zhihuuser.pipelines.MongoDBPipeline‘: 300,
}

pipelines.py：
　　1、首先我們要從settings文件中讀取數據的地址、端口、數據庫名稱（沒有會自動創建）。
　　2、拿到數據庫的基本信息後進行連接。
　　3、將數據寫入數據庫
　　4、關閉數據庫
　　註意：只有打開和關閉是只執行一次，而寫入操作會根據具體的寫入次數而定。

import pymongo

class MongoDBPipeline(object):
    """
    1、連接數據庫操作
    """
    def __init__(self,mongourl,mongoport,mongodb):
        ‘‘‘
        初始化mongodb數據的url、端口號、數據庫名稱
        :param mongourl:
        :param mongoport:
        :param mongodb:
        ‘‘‘
        self.mongourl = mongourl
        self.mongoport = mongoport
        self.mongodb = mongodb

    @classmethod
    def from_crawler(cls,crawler):
        """
        1、讀取settings裏面的mongodb數據的url、port、DB。
        :param crawler:
        :return:
        """
        return cls(
            mongourl = crawler.settings.get("MONGO_URL"),
            mongoport = crawler.settings.get("MONGO_PORT"),
            mongodb = crawler.settings.get("MONGO_DB")
        )

    def open_spider(self,spider):
        ‘‘‘
        1、連接mongodb數據
        :param spider:
        :return:
        ‘‘‘
        self.client = pymongo.MongoClient(self.mongourl,self.mongoport)
        self.db = self.client[self.mongodb]

    def process_item(self,item,spider):
        ‘‘‘
        1、將數據寫入數據庫
        :param item:
        :param spider:
        :return:
        ‘‘‘
        name = item.__class__.__name__
        # self.db[name].insert(dict(item))
        self.db[‘user‘].update({‘url_token‘:item[‘url_token‘]},{‘$set‘:item},True)
        return item

    def close_spider(self,spider):
        ‘‘‘
        1、關閉數據庫連接
        :param spider:
        :return:
        ‘‘‘
        self.client.close()

python爬蟲之scrapy的pipeline的使用