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。