Scrapy1.4最新官方文档总结 1 介绍·安装
Scrapy1.4最新官方文档总结 2 Tutorial
Scrapy1.4最新官方文档总结 3 命令行工具
这是官方文档的Tutorial（https://docs.scrapy.org/en/latest/intro/tutorial.html）。
推荐四个Python学习资源：
- Dive Into Python 3
- Python Tutorial
- Learn Python The Hard Way
- this list of Python resources for non-programmers
创建项目
使用命令：
scrapy startproject tutorial
会生成以下文件：
在tutorial/spiders文件夹新建文件quotes_spider.py，它的代码如下：
import scrapy
class QuotesSpider(scrapy.Spider):
name = "quotes"
def start_requests(self):
urls = [
'http://quotes.toscrape.com/page/1/',
'http://quotes.toscrape.com/page/2/',
]
for url in urls:
yield scrapy.Request(url=url, callback=self.parse)
def parse(self, response):
page = response.url.split("/")[-2]
filename = 'quotes-%s.html' % page
with open(filename, 'wb') as f:
f.write(response.body)
self.log('Saved file %s' % filename)
start_requests方法返回 scrapy.Request对象。每收到一个，就实例化一个Response对象，并调用和request绑定的调回方法（即parse），将response作为参数。
切换到根目录，运行爬虫：
scrapy crawl quotes
输出日志
根目录下会产生两个文件，quotes-1.html和quotes-2.html。
另一种方法是定义一个包含URLs的类，parse( )是Scrapy默认的调回方法，即使没有指明调回，也会执行：
import scrapy
class QuotesSpider(scrapy.Spider):
name = "quotes"
start_urls = [
'http://quotes.toscrape.com/page/1/',
'http://quotes.toscrape.com/page/2/',
]
def parse(self, response):
page = response.url.split("/")[-2]
filename = 'quotes-%s.html' % page
with open(filename, 'wb') as f:
f.write(response.body)
提取信息
学习Scrapy提取信息的最好方法是使用Scrapy Shell，win7 shell运行：
scrapy shell "http://quotes.toscrape.com/page/1/"
或者，gitbash运行，注意有单引号和双引号的区别：
scrapy shell 'http://quotes.toscrape.com/page/1/'
输出如下：
利用CSS进行提取：
>>> response.css('title')
[<Selector xpath='descendant-or-self::title' data='<title>Quotes to Scrape</title>'>]
只提取标题的文本：
>>> response.css('title::text').extract()
['Quotes to Scrape']
::text表示只提取文本，去掉的话，显示如下：
>>> response.css('title').extract()
['<title>Quotes to Scrape</title>']
因为返回对象是一个列表，只提取第一个的话，使用：
>>> response.css('title::text').extract_first()
'Quotes to Scrape'
或者，使用序号：
>>> response.css('title::text')[0].extract()
'Quotes to Scrape'
前者更好，可以避免潜在的序号错误。
除了使用 extract()和 extract_first()，还可以用正则表达式：
>>> response.css('title::text').re(r'Quotes.*')
['Quotes to Scrape']
>>> response.css('title::text').re(r'Q\w+')
['Quotes']
>>> response.css('title::text').re(r'(\w+) to (\w+)')
['Quotes', 'Scrape']
提取日志
XPath简短介绍
Scrapy还支持XPath：
>>> response.xpath('//title')
[<Selector xpath='//title' data='<title>Quotes to Scrape</title>'>]
>>> response.xpath('//title/text()').extract_first()
'Quotes to Scrape'
其实，CSS是底层转化为XPath的，但XPath的功能更为强大，比如它可以选择包含next page的链接。更多见 using XPath with Scrapy Selectors here。
继续提取名人名言
http://quotes.toscrape.com的每个名言的HTML结构如下：
<div class="quote">
<span class="text">“The world as we have created it is a process of our
thinking. It cannot be changed without changing our thinking.”</span>
<span>
by <small class="author">Albert Einstein</small>
<a href="/author/Albert-Einstein">(about)</a>
</span>
<div class="tags">
Tags:
<a class="tag" href="/tag/change/page/1/">change</a>
<a class="tag" href="/tag/deep-thoughts/page/1/">deep-thoughts</a>
<a class="tag" href="/tag/thinking/page/1/">thinking</a>
<a class="tag" href="/tag/world/page/1/">world</a>
</div>
</div>
使用：
$ scrapy shell "http://quotes.toscrape.com"
将HTML的元素以列表的形式提取出来：
response.css("div.quote")
只要第一个：
quote = response.css("div.quote")[0]
提取出标题、作者、标签：
>>> title = quote.css("span.text::text").extract_first()
>>> title
'“The world as we have created it is a process of our thinking. It cannot be changed without changing our thinking.”'
>>> author = quote.css("small.author::text").extract_first()
>>> author
'Albert Einstein'
标签是一组字符串：
>>> tags = quote.css("div.tags a.tag::text").extract()
>>> tags
['change', 'deep-thoughts', 'thinking', 'world']
弄明白了提取每个名言，现在提取所有的：
>>> for quote in response.css("div.quote"):
... text = quote.css("span.text::text").extract_first()
... author = quote.css("small.author::text").extract_first()
... tags = quote.css("div.tags a.tag::text").extract()
... print(dict(text=text, author=author, tags=tags))
{'tags': ['change', 'deep-thoughts', 'thinking', 'world'], 'author': 'Albert Einstein', 'text': '“The world as we have created it is a process of our thinking. It cannot be changed without changing our thinking.”'}
{'tags': ['abilities', 'choices'], 'author': 'J.K. Rowling', 'text': '“It is our choices, Harry, that show what we truly are, far more than our abilities.”'}
... a few more of these, omitted for brevity
>>>
用爬虫提取信息
使用Python的yield：
import scrapy
class QuotesSpider(scrapy.Spider):
name = "quotes"
start_urls = [
'http://quotes.toscrape.com/page/1/',
'http://quotes.toscrape.com/page/2/',
]
def parse(self, response):
for quote in response.css('div.quote'):
yield {
'text': quote.css('span.text::text').extract_first(),
'author': quote.css('small.author::text').extract_first(),
'tags': quote.css('div.tags a.tag::text').extract(),
}
运行爬虫，日志如下：
2016-09-19 18:57:19 [scrapy.core.scraper] DEBUG: Scraped from <200 http://quotes.toscrape.com/page/1/>
{'tags': ['life', 'love'], 'author': 'André Gide', 'text': '“It is better to be hated for what you are than to be loved for what you are not.”'}
2016-09-19 18:57:19 [scrapy.core.scraper] DEBUG: Scraped from <200 http://quotes.toscrape.com/page/1/>
{'tags': ['edison', 'failure', 'inspirational', 'paraphrased'], 'author': 'Thomas A. Edison', 'text': "“I have not failed. I've just found 10,000 ways that won't work.”"}
保存数据
最便捷的方式是使用feed export，保存为json，命令如下：
scrapy crawl quotes -o quotes.json
保存为json lines：
scrapy crawl quotes -o quotes.jl
保存为csv：
scrapy crawl quotes -o quotes.csv
提取下一页
首先看下一页的链接：
<ul class="pager">
<li class="next">
<a href="/page/2/">Next <span aria-hidden="true">→</span></a>
</li>
</ul>
提取出来：
>>> response.css('li.next a').extract_first()
'<a href="/page/2/">Next <span aria-hidden="true">→</span></a>'
只要href：
>>> response.css('li.next a::attr(href)').extract_first()
'/page/2/'
利用urljoin生成完整的url，生成下一页的请求，就可以循环抓取了：
import scrapy
class QuotesSpider(scrapy.Spider):
name = "quotes"
start_urls = [
'http://quotes.toscrape.com/page/1/',
]
def parse(self, response):
for quote in response.css('div.quote'):
yield {
'text': quote.css('span.text::text').extract_first(),
'author': quote.css('small.author::text').extract_first(),
'tags': quote.css('div.tags a.tag::text').extract(),
}
next_page = response.css('li.next a::attr(href)').extract_first()
if next_page is not None:
next_page = response.urljoin(next_page)
yield scrapy.Request(next_page, callback=self.parse)
更简洁的方式是使用 response.follow：
import scrapy
class QuotesSpider(scrapy.Spider):
name = "quotes"
start_urls = [
'http://quotes.toscrape.com/page/1/',
]
def parse(self, response):
for quote in response.css('div.quote'):
yield {
'text': quote.css('span.text::text').extract_first(),
'author': quote.css('span small::text').extract_first(),
'tags': quote.css('div.tags a.tag::text').extract(),
}
next_page = response.css('li.next a::attr(href)').extract_first()
if next_page is not None:
yield response.follow(next_page, callback=self.parse)
直接将参数传递给response.follow：
for href in response.css('li.next a::attr(href)'):
yield response.follow(href, callback=self.parse)
对于a标签，response.follow可以直接使用它的属性，这样就可以变得更简洁：
for a in response.css('li.next a'):
yield response.follow(a, callback=self.parse)
下面这个爬虫提取作者信息，使用了调回和自动获取下一页：
import scrapy
class AuthorSpider(scrapy.Spider):
name = 'author'
start_urls = ['http://quotes.toscrape.com/']
def parse(self, response):
# 作者链接
for href in response.css('.author + a::attr(href)'):
yield response.follow(href, self.parse_author)
# 分页链接
for href in response.css('li.next a::attr(href)'):
yield response.follow(href, self.parse)
def parse_author(self, response):
def extract_with_css(query):
return response.css(query).extract_first().strip()
yield {
'name': extract_with_css('h3.author-title::text'),
'birthdate': extract_with_css('.author-born-date::text'),
'bio': extract_with_css('.author-description::text'),
}
使用爬虫参数
在命令行中使用参数，只要添加 -a：
scrapy crawl quotes -o quotes-humor.json -a tag=humor
将humor传递给tag：
import scrapy
class QuotesSpider(scrapy.Spider):
name = "quotes"
def start_requests(self):
url = 'http://quotes.toscrape.com/'
tag = getattr(self, 'tag', None)
if tag is not None:
url = url + 'tag/' + tag
yield scrapy.Request(url, self.parse)
def parse(self, response):
for quote in response.css('div.quote'):
yield {
'text': quote.css('span.text::text').extract_first(),
'author': quote.css('small.author::text').extract_first(),
}
next_page = response.css('li.next a::attr(href)').extract_first()
if next_page is not None:
yield response.follow(next_page, self.parse)
更多例子
https://github.com/scrapy/quotesbot上有个叫做quotesbot的爬虫，提供了CSS和XPath两种写法：
import scrapy
class ToScrapeCSSSpider(scrapy.Spider):
name = "toscrape-css"
start_urls = [
'http://quotes.toscrape.com/',
]
def parse(self, response):
for quote in response.css("div.quote"):
yield {
'text': quote.css("span.text::text").extract_first(),
'author': quote.css("small.author::text").extract_first(),
'tags': quote.css("div.tags > a.tag::text").extract()
}
next_page_url = response.css("li.next > a::attr(href)").extract_first()
if next_page_url is not None:
yield scrapy.Request(response.urljoin(next_page_url))
import scrapy
class ToScrapeSpiderXPath(scrapy.Spider):
name = 'toscrape-xpath'
start_urls = [
'http://quotes.toscrape.com/',
]
def parse(self, response):
for quote in response.xpath('//div[@class="quote"]'):
yield {
'text': quote.xpath('./span[@class="text"]/text()').extract_first(),
'author': quote.xpath('.//small[@class="author"]/text()').extract_first(),
'tags': quote.xpath('.//div[@class="tags"]/a[@class="tag"]/text()').extract()
}
next_page_url = response.xpath('//li[@class="next"]/a/@href').extract_first()
if next_page_url is not None:
yield scrapy.Request(response.urljoin(next_page_url))
Scrapy1.4最新官方文档总结 1 介绍·安装
Scrapy1.4最新官方文档总结 2 Tutorial
Scrapy1.4最新官方文档总结 3 命令行工具
