python爬虫scrapy框架——爬取伯乐在线网站文章

一、前言 

1. scrapy依赖包：

二、创建工程

1. 创建scrapy工程：

scrapy staratproject ArticleSpider

2. 开始（创建）新的爬虫：

cd ArticleSpider
scrapy genspider jobbole blog.jobbole.com //默认通过 'basic' module创建

三、用pycharm调试scrapy

1. 在 ArticleSpider 目录下创建 main.py 文件

2. 用到Python提供的一个内置函数，调用这个函数可以执行scrapy脚本

from scrapy.cmdline import execute

import sys
import os

sys.path.append(os.path.dirname(os.path.abspath(__file__)))
execute(["scrapy", "crawl", "jobbole"])

#需要把当前项目目录放到sys.path下，scrapy命令必须在工程目录下运行
#__file__:当前文件（main.py文件）
#os.path.abspath(__file__): 获取main.py的绝对路径
#os.path.dirname(os.path.abspath(__file__)):获取mian.py目录
#scrapy启动命令：scrapy crawl jobbole

3. 现在就可以在pycharm中打断点使用debug模式了

四、Settings.py 配置

1. 在 settings.py 文件中找到 ROBOTSTXT_OBEY , 把其值设为 False。让我们的爬虫不去读取网站的 ROBOTS 协议。

五、Xpath语法

注：尽量不用beautifulsoup，它比Xpath慢许多

表达式	说明
article	选取所有的article元素的所有子节点
/article	选取根元素article
article/a	选取所有属于article的子元素的a元素
//div	选取所有div子元素（不论出现在文档任何地方）
article//div	选取所有属于article元素的后代的div元素，不管它出现在article的任何位置
//@class	选取所有名为class的属性

表达式	说明
/article/div[1]	选择属于article子元素的第一个div元素
/article/div[last()]	选择属于article子元素的最后一个div元素
/article/div[last()-1]	选择属于article子元素的倒数第二个div元素
//div[@lang]	选择所有拥有lang属性的div元素
//div[@lang='eng']	选取所有lang属性为eng的div元素
/div/*	选取属于div元素的所有子节点
//*	选取所有元素
//div[@*]	选取所有带属性的div元素
/div/a|//div/p	选取所有div元素的a和p元素
//span|//ul	选取文档中的span和ul元素
article/div/p|//span	选取所有属于article元素的div元素的p元素 以及文档中所有的span元素
//h1[@id='test']/text()	获取id为test的h1的文字

 六、用Xpath和CSS爬取伯乐在线文章页面元素

# jobbole.py
import scrapy
import re

class JobboleSpider(scrapy.Spider):
    name = 'jobbole'
    allowed_domains = ['blog.jobbole.com']
    start_urls = ['http://blog.jobbole.com/110287/']

    def parse(self, response):
        # 通过Xpath提取字段

        title = response.xpath(".//*[@id='post-110287']/div[1]/h1/text()").extract_first()
        create_date = response.xpath("//p[@class='entry-meta-hide-on-mobile']/text()").extract_first().strip().replace('·', '').strip()
        praise_nums = response.xpath("//span[contains(@class, 'vote-post-up')]/h10/text()").extract_first()
        fav_nums = response.xpath("//span[contains(@class, 'bookmark-btn')]/text()").extract_first()
        match_re = re.match(r'.*?(\d+).*', fav_nums)
        if match_re:
            fav_nums = match_re.group(1)
        comment_nums = response.xpath("//a[@href='#article-comment']/text()").extract()[0]
        match_re = re.match(r'.*?(\d+).*', comment_nums)
        if match_re:
            comment_nums = match_re.group(1)

        content = response.xpath("//div[@class='entry']").extract()[0]
        tag_list = response.xpath("//p[@class='entry-meta-hide-on-mobile']/a/text()").extract()
        tag_list = [element for element in tag_list if not element.strip().endswith('评论')]
        tags = ','.join(tag_list)

        # 通过CSS选择器提取字段

        title = response.css(".entry-header h1::text").extract()
        create_date = response.css("p.entry-meta-hide-on-mobile::text").extract()[0].strip().replace('·', '').strip()
        praise_nums = response.css(".vote-post-up h10::text").extract()[0]
        fav_nums = response.css(".bookmark-btn::text").extract()[0]
        match_re = re.match(r'.*?(\d+).*', fav_nums)
        if match_re:
            fav_nums = match_re.group(1)
        comment_nums = response.css("a[href='#article-comment'] span::text").extract()[0]
        match_re = re.match(r'.*?(\d+).*', comment_nums)
        if match_re:
            comment_nums = match_re.group(1)
        content = response.css("div.entry").extract()[0]
        tag_list = response.css("p.entry-meta-hide-on-mobile a::text").extract()
        tag_list = [element for element in tag_list if not element.strip().endswith('评论')]
        tags = ','.join(tag_list)    

七、利用ItemLoader爬取伯乐在线文章页面元素

# jobbole.py
import scrapy
import re
import datetime
from scrapy.http import Request
from urllib import parse
from scrapy.loader import ItemLoader

from ArticleSpider.items import JobBoleArticleItem, ArticleItemLoader
from ArticleSpider.utils.common import get_md5

class JobboleSpider(scrapy.Spider):
    name = 'jobbole'
    allowed_domains = ['blog.jobbole.com']
    start_urls = ['http://blog.jobbole.com/all-posts/']

    def parse(self, response):
        """
        1. 获取文章列表页中的文章url并交给scrapy下载后进行解析
        2. 获取下一页的url并交给scrapy进行下载，下载完成后交给parse
        """

        # 解析列表页中的所有文章url并交给scrapy下载后进行解析
        post_nodes = response.css("#archive .floated-thumb .post-thumb a")
        for post_node in post_nodes:
            img_url = post_node.css("img::attr(src)").extract_first("")
            post_url = post_node.css("::attr(href)").extract_first("")
            yield Request(url=parse.urljoin(response.url, post_url), meta={"front_image_url": img_url}, callback=self.parse_detail)

        # 提取下一页并交给scrapy进行下载
        next_url = response.css(".next.page-numbers::attr(href)").extract_first()
        if next_url:
            yield Request(url=parse.urljoin(response.url, next_url), callback=self.parse)

    def parse_detail(self, response):
        article_item = JobBoleArticleItem()

        # 通过Item_Loader加载Item
        item_loader = ArticleItemLoader(item=JobBoleArticleItem(), response=response)
        item_loader.add_css('title', '.entry-header h1::text')
        item_loader.add_value('url', response.url)
        item_loader.add_value('url_object_id', get_md5(response.url))
        item_loader.add_css('create_date', 'p.entry-meta-hide-on-mobile::text')
        item_loader.add_value('front_image_url', response.meta.get("front_image_url", ""))
        item_loader.add_css('praise_nums', '.vote-post-up h10::text')
        item_loader.add_css('comment_nums', "a[href='#article-comment'] span::text")
        item_loader.add_css('fav_nums', '.bookmark-btn::text')
        item_loader.add_css('tags', 'p.entry-meta-hide-on-mobile a::text')
        item_loader.add_css('content', 'div.entry')
        article_item = item_loader.load_item()

        yield article_item

# items.py
# -*- coding: utf-8 -*-

# Define here the models for your scraped items
#
# See documentation in:
# http://doc.scrapy.org/en/latest/topics/items.html
import datetime
import re

import scrapy
from scrapy.loader import ItemLoader
from scrapy.loader.processors import MapCompose, TakeFirst, Join

class ArticlespiderItem(scrapy.Item):
    # define the fields for your item here like:
    # name = scrapy.Field()
    pass

def add_jobbole(value):
    return value+'-bobby'

def data_convert(value):
    try:
        create_date = datetime.datetime.strptime(value, '%Y/%m/%d').date()
    except Exception as e:
        create_date = datetime.datetime.now().date()

    return create_date

def get_nums(value):
    match_re = re.match(r'.*?(\d+).*', value)
    if match_re:
        nums = match_re.group(1)
    else:
        nums = 0

    return nums

def remove_comment_tags(value):
    # 去掉tag中提取的“评论”
    if '评论' in value:
        return ''
    return value

def return_value(value):
    return value

class ArticleItemLoader(ItemLoader):
    # 自定义item_loader
    default_output_processor = TakeFirst()

class JobBoleArticleItem(scrapy.Item):
    title = scrapy.Field(
        input_processor=MapCompose(lambda x:x+'-jobbole', add_jobbole)
    )
    create_date = scrapy.Field(
        input_processor=MapCompose(data_convert)
    )
    url = scrapy.Field()
    url_object_id = scrapy.Field()
    front_image_url = scrapy.Field(
        output_processor=MapCompose(return_value)
    )
    front_image_path = scrapy.Field()
    praise_nums = scrapy.Field(
        input_processor=MapCompose(get_nums)
    )
    comment_nums = scrapy.Field(
        input_processor=MapCompose(get_nums)
    )
    fav_nums = scrapy.Field(
        input_processor=MapCompose(get_nums)
    )
    tags = scrapy.Field(
        input_processor=MapCompose(remove_comment_tags),
        output_processor=Join(',')
    )
    content = scrapy.Field()

# pipeline.py
# -*- coding: utf-8 -*-

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

from scrapy.pipelines.images import ImagesPipeline
from scrapy.exporters import JsonItemExporter
from twisted.enterprise import adbapi

class ArticlespiderPipeline(object):
    def process_item(self, item, spider):
        return item

class JsonWithEncodingPipeline:
    # 自定义Json文件的导出
    def __init__(self):
        self.file = codecs.open('article.json', 'w', encoding='utf-8')

    def process_item(self, item, spider):
        lines = json.dumps(dict(item), ensure_ascii=False) + '\n'
        self.file.write(lines)
        return item

    def spider_closed(self, spider):
        self.file.close()

class JsonExporterPipeline(object):
    # 调用scripy提供的JsonExporter导出Json文件
    def __init__(self):
        self.file = open('articleExporter.json', 'wb')
        self.exporter = JsonItemExporter(self.file, encoding='utf-8', ensure_ascii=False)
        self.exporter.start_exporting()

    def close_spider(self, spider):
        self.exporter.finish_exporting()
        self.file.close()

    def process_item(self, item, spider):
        self.exporter.export_item(item)
        return item

class MysqlPipeline(object):
    # 采用同步的机制写入MySQL

    def __init__(self):
        self.conn = MySQLdb.connect('127.0.0.1', 'root', '', 'article_spider', charset='utf8', use_unicode=True)
        self.cursor = self.conn.cursor()

    def process_item(self, item, spider):
        insert_sql = """
        insert into jobbole_article(url_object_id, title, url, create_date, fav_nums)
        Values ("%s", "%s", "%s", "%s", "%s")
        """
        self.cursor.execute(insert_sql % (item['url_object_id'], item['title'], item['url'], item['create_date'], item['fav_nums']))
        self.conn.commit()
        return item

class MysqlTwistedPipeline(object):
    def __init__(self, dbpool):
        self.dbpool = dbpool

    @classmethod
    def from_settings(cls, settings):
        dbparms = dict(
            host=settings['MYSQL_HOST'],
            db=settings['MYSQL_DBNAME'],
            user=settings['MYSQL_USER'],
            passwd=settings['MYSQL_PASSWORD'],
            charset='utf8',
            cursorclass=MySQLdb.cursors.DictCursor,
            use_unicode=True
        )

        dbpool = adbapi.ConnectionPool('MySQLdb', **dbparms)
        return cls(dbpool)

    def process_item(self, item, spider):
        # 使用Twisted将MySQL插入变成异步执行
        query = self.dbpool.runInteraction(self.do_insert, item)
        query.addErrback(self.handle_error)
        return item

    def handle_error(self, failure):
        # 处理异步插入的异常
        print(failure)

    def do_insert(self, cursor, item):
        # 执行具体的插入
        insert_sql = """
                insert into jobbole_article(url_object_id, title, url, create_date, fav_nums)
                Values ("%s", "%s", "%s", "%s", "%s")
                """
        cursor.execute(insert_sql % (item['url_object_id'], item['title'], item['url'], item['create_date'], item['fav_nums']))
        cursor.commit()

class ArticleImagePipeline(ImagesPipeline):
    def item_completed(self, results, item, info):
        if 'front_image_url' in item:
            for ok, value in results:
                image_file_path = value['path']
            item['front_image_path'] = image_file_path
        return item

#utils/common.py

import hashlib

def get_md5(url):
    if isinstance(url, str):
        url = url.encode('utf-8')
    m = hashlib.md5()
    m.update(url)
    return m.hexdigest()

if __name__ == '__main__':
    print(get_md5('http://jobbole.com'))

# settings.py

import os

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

BOT_NAME = 'ArticleSpider'

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

# Crawl responsibly by identifying yourself (and your website) on the user-agent
#USER_AGENT = 'ArticleSpider (+http://www.yourdomain.com)'

# Obey robots.txt rules
ROBOTSTXT_OBEY = False

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

# Configure a delay for requests for the same website (default: 0)
# See http://scrapy.readthedocs.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 http://scrapy.readthedocs.org/en/latest/topics/spider-middleware.html
#SPIDER_MIDDLEWARES = {
#    'ArticleSpider.middlewares.ArticlespiderSpiderMiddleware': 543,
#}

# Enable or disable downloader middlewares
# See http://scrapy.readthedocs.org/en/latest/topics/downloader-middleware.html
#DOWNLOADER_MIDDLEWARES = {
#    'ArticleSpider.middlewares.MyCustomDownloaderMiddleware': 543,
#}

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

# Configure item pipelines
# See http://scrapy.readthedocs.org/en/latest/topics/item-pipeline.html
ITEM_PIPELINES = {
    # 'ArticleSpider.pipelines.JsonExporterPipeline': 2,
    # 'scrapy.pipelines.images.ImagesPipeline': 1,
    'ArticleSpider.pipelines.ArticleImagePipeline': 2,
    'ArticleSpider.pipelines.MysqlPipeline': 1,
}
IMAGES_URLS_FIELD = 'front_image_url'
project_dir = os.path.abspath(os.path.dirname(__file__))
IMAGES_STORE = os.path.join(project_dir, "images")

# IMAGES_MIN_HEIGHT = 100
# IMAGES_MIN_WIDTH = 100

# Enable and configure the AutoThrottle extension (disabled by default)
# See http://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 http://scrapy.readthedocs.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'

MYSQL_HOST = '172.0.0.1'
MYSQL_DBNAME = 'article_spider'
MYSQL_USER = 'root'
MYSQL_PASSWORD = ''