1. Scrapy框架

　　Scrapy是python下實現爬蟲功能的框架，能夠將數據解析、數據處理、數據存儲合為一體功能的爬蟲框架。

2. Scrapy安裝

1. 安裝依賴包

yum install gcc libffi-devel python-devel openssl-devel -y
yum install libxslt-devel -y

 2. 安裝scrapy

pip install scrapy
pip install twisted==13.1.0

 註意事項：scrapy和twisted存在相容性問題，如果安裝twisted版本過高，運行scrapy startproject project_name的時候會提示報錯，安裝twisted==13.1.0即可。

3. 基於Scrapy爬取數據並存入到CSV

3.1. 爬蟲目標，獲取簡書中熱門專題的數據信息，站點為https://www.jianshu.com/recommendations/collections，點擊"熱門"是我們需要爬取的站點，該站點使用了AJAX非同步載入技術，通過F12鍵——Network——XHR，並翻頁獲取到頁面URL地址為https://www.jianshu.com/recommendations/collections?page=2&order_by=hot，通過修改page=後面的數值即可訪問多頁的數據，如下圖：

3.2. 爬取內容

　　需要爬取專題的內容包括：專題內容、專題描述、收錄文章數、關註人數，Scrapy使用xpath來清洗所需的數據，編寫爬蟲過程中可以手動通過lxml中的xpath獲取數據，確認無誤後再將其寫入到scrapy代碼中，區別點在於，scrapy需要使用extract()函數才能將數據提取出來。

3.3 創建爬蟲項目

[root@HappyLau jianshu_hot_topic]# scrapy startproject jianshu_hot_topic

#項目目錄結構如下:
[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    #手動創建文件，用於爬蟲數據提取
│       └── jianshu_hot_topic_spider.pyc
└── scrapy.cfg

2 directories, 16 files
[root@HappyLau python]# 

 3.4 代碼內容

1. items.py代碼內容,定義需要爬取數據欄位
# -*- 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，繼承父類scrapy.Item的屬性和方法，該類用於定義需要爬取數據的子段
	'''
	collection_name = Field()
	collection_description = Field()
	collection_article_count = Field()
	collection_attention_count = Field()

2. piders/jianshu_hot_topic_spider.py代碼內容，實現數據獲取的代碼邏輯，通過xpath實現
[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):
	'''
	簡書專題數據爬取，獲取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中特定欄位信息
		'''
		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("人關註",'').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文件內容，定義數據存儲的方式，此處定義數據存儲的邏輯，可以將數據存儲載MySQL資料庫，MongoDB資料庫，文件，CSV，Excel等存儲介質中，如下以存儲載CSV為例：
[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 運行scrapy爬蟲

　　返回到項目scrapy項目創建所在目錄，運行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中的數據，即可實現。

4. 遇到的問題總結

1. twisted版本不見容，安裝過新的版本導致，安裝Twisted (13.1.0)即可

2. 中文數據無法寫入，提示'ascii'錯誤，通過設置python的encoding為utf即可，如下：

>>> import sys
>>> sys.getdefaultencoding()
'ascii'
>>> reload(sys)
<module 'sys' (built-in)>
>>> sys.setdefaultencoding('utf8')
>>> sys.getdefaultencoding()
'utf8'

 3. 爬蟲無法獲取站點數據，由於headers導致，載settings.py文件中添加USER_AGENT變數，如：

USER_AGENT="Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Firefox/52.0"

 Scrapy使用過程中可能會遇到結果執行失敗或者結果執行不符合預期，其現實的logs非常詳細，通過觀察日誌內容，並結合代碼+網上搜索資料即可解決。