Python使用Scrapy框架爬取数据存入CSV文件(Python爬虫实战4)
1. Scrapy框架
Scrapy是python下实现爬虫功能的框架，能够将数据解析、数据处理、数据存储合为一体功能的爬虫框架。
2. Scrapy安装
1. 安装依赖包
yum install gcc libffi-devel python-devel openssl-devel -y yum install libxslt-devel -y
2. 安装scrapy
pip install scrapy
pip install twisted==13.1.0
注意事项：scrapy和twisted存在兼容性问题，如果安装twisted版本过高，运行scrapy startproject project_name的时候会提示报错，安装twisted==13.1.0即可。
3. 基于Scrapy爬取数据并存入到CSV
3.1. 爬虫目标，获取简书中热门专题的数据信息，站点为https://www.jianshu.com/recommendations/collections，点击"热门"是我们需要爬取的站点，该站点使用了AJAX异步加载技术，通过F12键——Network——XHR，并翻页获取到页面URL地址为https://www.jianshu.com/recommendations/collections?page=2&order_by=hot，通过修改page=后面的数值即可访问多页的数据，如下图：
3.2. 爬取内容
需要爬取专题的内容包括：专题内容、专题描述、收录文章数、关注人数，Scrapy使用xpath来清洗所需的数据，编写爬虫过程中可以手动通过lxml中的xpath获取数据，确认无误后再将其写入到scrapy代码中，区别点在于，scrapy需要使用extract()函数才能将数据提取出来。
3.3 创建爬虫项目
[root@HappyLau jianshu_hot_topic]# scrapy startproject jianshu_hot_topic #项目目录结构如下: [root@HappyLau python]# tree jianshu_hot_topic jianshu_hot_topic ├── jianshu_hot_topic │ ├── __init__.py │ ├── __init__.pyc │ ├── items.py │ ├── items.pyc │ ├── middlewares.py │ ├── pipelines.py │ ├── pipelines.pyc │ ├── settings.py │ ├── settings.pyc │ └── spiders │ ├── collection.py │ ├── collection.pyc │ ├── __init__.py │ ├── __init__.pyc │ ├── jianshu_hot_topic_spider.py #手动创建文件，用于爬虫数据提取 │ └── jianshu_hot_topic_spider.pyc └── scrapy.cfg 2 directories, 16 files [root@HappyLau python]#
3.4 代码内容
1. items.py代码内容,定义需要爬取数据字段
# -*- coding: utf-8 -*-
# Define here the models for your scraped items
#
# See documentation in:
# https://doc.scrapy.org/en/latest/topics/items.html
import scrapy
from scrapy import Item
from scrapy import Field
class JianshuHotTopicItem(scrapy.Item):
'''
@scrapy.item，继承父类scrapy.Item的属性和方法，该类用于定义需要爬取数据的子段
'''
collection_name = Field()
collection_description = Field()
collection_article_count = Field()
collection_attention_count = Field()
2. piders/jianshu_hot_topic_spider.py代码内容，实现数据获取的代码逻辑，通过xpath实现
[root@HappyLau jianshu_hot_topic]# cat spiders/jianshu_hot_topic_spider.py
#_*_ coding:utf8 _*_
import random
from time import sleep
from scrapy.spiders import CrawlSpider
from scrapy.selector import Selector
from scrapy.http import Request
from jianshu_hot_topic.items import JianshuHotTopicItem
class jianshu_hot_topic(CrawlSpider):
'''
简书专题数据爬取，获取url地址中特定的子段信息
'''
name = "jianshu_hot_topic"
start_urls = ["https://www.jianshu.com/recommendations/collections?page=2&order_by=hot"]
def parse(self,response):
'''
@params:response,提取response中特定字段信息
'''
item = JianshuHotTopicItem()
selector = Selector(response)
collections = selector.xpath('//div[@class="col-xs-8"]')
for collection in collections:
collection_name = collection.xpath('div/a/h4/text()').extract()[0].strip()
collection_description = collection.xpath('div/a/p/text()').extract()[0].strip()
collection_article_count = collection.xpath('div/div/a/text()').extract()[0].strip().replace('篇文章','')
collection_attention_count = collection.xpath('div/div/text()').extract()[0].strip().replace("人关注",'').replace("· ",'')
item['collection_name'] = collection_name
item['collection_description'] = collection_description
item['collection_article_count'] = collection_article_count
item['collection_attention_count'] = collection_attention_count
yield item
urls = ['https://www.jianshu.com/recommendations/collections?page={}&order_by=hot'.format(str(i)) for i in range(3,11)]
for url in urls:
sleep(random.randint(2,7))
yield Request(url,callback=self.parse)
3. pipelines文件内容，定义数据存储的方式，此处定义数据存储的逻辑，可以将数据存储载MySQL数据库，MongoDB数据库，文件，CSV，Excel等存储介质中，如下以存储载CSV为例：
[root@HappyLau jianshu_hot_topic]# cat pipelines.py
# -*- 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
import csv
class JianshuHotTopicPipeline(object):
def process_item(self, item, spider):
f = file('/root/zhuanti.csv','a+')
writer = csv.writer(f)
writer.writerow((item['collection_name'],item['collection_description'],item['collection_article_count'],item['collection_attention_count']))
return item
4. 修改settings文件，
ITEM_PIPELINES = {
'jianshu_hot_topic.pipelines.JianshuHotTopicPipeline': 300,
}
3.5 运行scrapy爬虫
返回到项目scrapy项目创建所在目录，运行scrapy crawl spider_name即可，如下：
[root@HappyLau jianshu_hot_topic]# pwd
/root/python/jianshu_hot_topic
[root@HappyLau jianshu_hot_topic]# scrapy crawl jianshu_hot_topic
2018-02-24 19:12:23 [scrapy.utils.log] INFO: Scrapy 1.5.0 started (bot: jianshu_hot_topic)
2018-02-24 19:12:23 [scrapy.utils.log] INFO: Versions: lxml 3.2.1.0, libxml2 2.9.1, cssselect 1.0.3, parsel 1.4.0, w3lib 1.19.0, Twisted 13.1.0, Python 2.7.5 (default, Aug 4 2017, 00:39:18) - [GCC 4.8.5 20150623 (Red Hat 4.8.5-16)], pyOpenSSL 0.13.1 (OpenSSL 1.0.1e-fips 11 Feb 2013), cryptography 1.7.2, Platform Linux-3.10.0-693.el7.x86_64-x86_64-with-centos-7.4.1708-Core
2018-02-24 19:12:23 [scrapy.crawler] INFO: Overridden settings: {'NEWSPIDER_MODULE': 'jianshu_hot_topic.spiders', 'SPIDER_MODULES': ['jianshu_hot_topic.spiders'], 'ROBOTSTXT_OBEY': True, 'USER_AGENT': 'Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Firefox/52.0', 'BOT_NAME': 'jianshu_hot_topic'}
查看/root/zhuanti.csv中的数据，即可实现。
4. 遇到的问题总结
1. twisted版本不见容，安装过新的版本导致，安装Twisted (13.1.0)即可
2. 中文数据无法写入，提示'ascii'错误，通过设置python的encoding为utf即可，如下：
>>> import sys
>>> sys.getdefaultencoding()
'ascii'
>>> reload(sys)
<module 'sys' (built-in)>
>>> sys.setdefaultencoding('utf8')
>>> sys.getdefaultencoding()
'utf8'
3. 爬虫无法获取站点数据，由于headers导致，载settings.py文件中添加USER_AGENT变量，如：
USER_AGENT="Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Firefox/52.0"
Scrapy使用过程中可能会遇到结果执行失败或者结果执行不符合预期，其现实的logs非常详细，通过观察日志内容，并结合代码+网上搜索资料即可解决。
