python之scrapy模块pipelines

1、知识点

""""
pipelines使用：
    1、在spiders里面使用yield生成器
        list_li = response.xpath("//div[@class='swiper-wrapper']//li")
        #print(list_li)
        for li in list_li:
            #print(li.extract_first())
            item = { }
            item["name"] = li.xpath(".//h3/text()").extract_first()
            item["content"] = li.xpath(".//p[@class='teacherBrief']/text()").extract_first()
            #item["content"] = li.xpath(".//p[@class='teacherIntroduction']/text()").extract_first()
            #print(item)
            yield  item  #将数据传递道pipelines

    2、在pipelines中打印item
            class MyspiderPipeline(object):
                """
                #第一个管道，这个process_item方法名是不能改
                """
                def process_item(self, item, spider):
                    item["hello"] = "world"
                    print(item)
                    return item

            class MyspiderPipeline1(object):
                """
                #第二个管道
                """
                def process_item(self, item, spider):
                    print(item)
                    return item

    3、在settings文件添加pipelines的支持
        ITEM_PIPELINES = {
            #执行顺序为从小到大，即先执行300，然后在301
           'myspider.pipelines.MyspiderPipeline': 300,
            'myspider.pipelines.MyspiderPipeline1': 301,
        }
"""

2、spider.py文件中通过

yield  item  #将数据传递道pipelines.py中的item

JulyeduSpider.py文件代码

# -*- coding: utf-8 -*-
import scrapy
import  logging

logger = logging.getLogger(__name__)
class JulyeduSpider(scrapy.Spider):
    name = 'julyedu'
    allowed_domains = ['julyedu.com']
    start_urls = ['http://julyedu.com/']
    #这个parse方法名不能改
    def parse(self, response):
        """
        爬虫七月在线的导师名单
        :param response:
        :return:
        """
        list_li = response.xpath("//div[@class='swiper-wrapper']//li")
        #print(list_li)
        item = {}
        for li in list_li:
            item["name"] = li.xpath(".//h3/text()").extract_first()
            item["content"] = li.xpath(".//p[@class='teacherBrief']/text()").extract_first()
            #item["content"] = li.xpath(".//p[@class='teacherIntroduction']/text()").extract_first()
            #print(item)
            #将数据传递道pipelines，yield只接受Request,BaseItem，dict,None四种类型
            logger.warning(item) #打印日志
            yield  item

2、修改pipelines.py文件，对其中的item可以操作

# -*- coding: utf-8 -*-

# Define your item pipelines here
#
# Don't forget to add your pipeline to the ITEM_PIPELINES setting
# See: https://doc.scrapy.org/en/latest/topics/item-pipeline.html

class MyspiderPipeline(object):
    """
    第一个管道，这个process_item方法名是不能改
    """
    def process_item(self, item, spider):
        """
        针对不同的爬虫的数据处理
        :param item:spider 传过来的值
        :param spider: 传递过来spider的类
        :return:
        """
        if spider.name == "julyedu":
            #print(item)
            return item
        else:
            return item

class MyspiderPipeline1(object):
    """
    第二个管道
    """
    def process_item(self, item, spider):
        #print(item)
        return item

3、对settings.py文件添加pipelines配置

# -*- coding: utf-8 -*-

# Scrapy settings for myspider project
#
# For simplicity, this file contains only settings considered important or
# commonly used. You can find more settings consulting the documentation:
#
#     https://doc.scrapy.org/en/latest/topics/settings.html
#     https://doc.scrapy.org/en/latest/topics/downloader-middleware.html
#     https://doc.scrapy.org/en/latest/topics/spider-middleware.html

BOT_NAME = 'myspider'

SPIDER_MODULES = ['myspider.spiders']
NEWSPIDER_MODULE = 'myspider.spiders'

LOG_LEVEL = 'WARNING'  #增加log日志
LOG_FILE='./log.log'  #将log日志保存到文件中
# Crawl responsibly by identifying yourself (and your website) on the user-agent
#USER_AGENT = 'myspider (+http://www.yourdomain.com)'

# Obey robots.txt rules
ROBOTSTXT_OBEY = True

# Configure maximum concurrent requests performed by Scrapy (default: 16)
#CONCURRENT_REQUESTS = 32

# Configure a delay for requests for the same website (default: 0)
# See https://doc.scrapy.org/en/latest/topics/settings.html#download-delay
# See also autothrottle settings and docs
#DOWNLOAD_DELAY = 3
# The download delay setting will honor only one of:
#CONCURRENT_REQUESTS_PER_DOMAIN = 16
#CONCURRENT_REQUESTS_PER_IP = 16

# Disable cookies (enabled by default)
#COOKIES_ENABLED = False

# Disable Telnet Console (enabled by default)
#TELNETCONSOLE_ENABLED = False

# Override the default request headers:
#DEFAULT_REQUEST_HEADERS = {
#   'Accept': 'text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8',
#   'Accept-Language': 'en',
#}

# Enable or disable spider middlewares
# See https://doc.scrapy.org/en/latest/topics/spider-middleware.html
#SPIDER_MIDDLEWARES = {
#    'myspider.middlewares.MyspiderSpiderMiddleware': 543,
#}

# Enable or disable downloader middlewares
# See https://doc.scrapy.org/en/latest/topics/downloader-middleware.html
#DOWNLOADER_MIDDLEWARES = {
#    'myspider.middlewares.MyspiderDownloaderMiddleware': 543,
#}

# Enable or disable extensions
# See https://doc.scrapy.org/en/latest/topics/extensions.html
#EXTENSIONS = {
#    'scrapy.extensions.telnet.TelnetConsole': None,
#}

# Configure item pipelines
# See https://doc.scrapy.org/en/latest/topics/item-pipeline.html
ITEM_PIPELINES = {
    #执行顺序为从小到大，即先执行300，然后在301
   'myspider.pipelines.MyspiderPipeline': 300,
    'myspider.pipelines.MyspiderPipeline1': 301,
}

# Enable and configure the AutoThrottle extension (disabled by default)
# See https://doc.scrapy.org/en/latest/topics/autothrottle.html
#AUTOTHROTTLE_ENABLED = True
# The initial download delay
#AUTOTHROTTLE_START_DELAY = 5
# The maximum download delay to be set in case of high latencies
#AUTOTHROTTLE_MAX_DELAY = 60
# The average number of requests Scrapy should be sending in parallel to
# each remote server
#AUTOTHROTTLE_TARGET_CONCURRENCY = 1.0
# Enable showing throttling stats for every response received:
#AUTOTHROTTLE_DEBUG = False

# Enable and configure HTTP caching (disabled by default)
# See https://doc.scrapy.org/en/latest/topics/downloader-middleware.html#httpcache-middleware-settings
#HTTPCACHE_ENABLED = True
#HTTPCACHE_EXPIRATION_SECS = 0
#HTTPCACHE_DIR = 'httpcache'
#HTTPCACHE_IGNORE_HTTP_CODES = []
#HTTPCACHE_STORAGE = 'scrapy.extensions.httpcache.FilesystemCacheStorage'