scrapy框架 小知识
持久化
步骤
pipeline/items
a. 先写pipeline类
class XXXPipeline(object):
def process_item(self, item, spider):
return item
b. 写Item类
class XdbItem(scrapy.Item):
href = scrapy.Field()
title = scrapy.Field()
c. 配置
ITEM_PIPELINES = {
'xdb.pipelines.XdbPipeline': 300,
}
d. 爬虫，yield每执行一次，process_item就调用一次。
yield Item对象
编写pipeline
from scrapy.exceptions import DropItem
class FilePipeline(object):
def __init__(self,path):
self.f = None
self.path = path
@classmethod
def from_crawler(cls, crawler):
"""
初始化时候，用于创建pipeline对象
:param crawler:
:return:
"""
print('File.from_crawler')
path = crawler.settings.get('HREF_FILE_PATH')
return cls(path)
def open_spider(self,spider):
"""
爬虫开始执行时，调用
:param spider:
:return:
"""
print('File.open_spider')
self.f = open(self.path,'a+')
def process_item(self, item, spider):
# f = open('xx.log','a+')
# f.write(item['href']+'\n')
# f.close()
print('File',item['href'])
self.f.write(item['href']+'\n')
# return item # 交给下一个pipeline的process_item方法
raise DropItem()# 后续的 pipeline的process_item方法不再执行
def close_spider(self,spider):
"""
爬虫关闭时，被调用
:param spider:
:return:
"""
print('File.close_spider')
self.f.close()
注意：pipeline是所有爬虫公用，如果想要给某个爬虫定制需要使用spider参数自己进行处理。
去重规则
编写类
from scrapy.dupefilter import BaseDupeFilter
from scrapy.utils.request import request_fingerprint
class XdbDupeFilter(BaseDupeFilter):
def __init__(self):
self.visited_fd = set()
@classmethod
def from_settings(cls, settings):
return cls()
def request_seen(self, request):
fd = request_fingerprint(request=request)
if fd in self.visited_fd:
return True
self.visited_fd.add(fd)
def open(self): # can return deferred
print('开始')
def close(self, reason): # can return a deferred
print('结束')
# def log(self, request, spider): # log that a request has been filtered
# print('日志')
配置
# 修改默认的去重规则 # DUPEFILTER_CLASS = 'scrapy.dupefilter.RFPDupeFilter' DUPEFILTER_CLASS = 'xdb.dupefilters.XdbDupeFilter'
爬虫使用
class ChoutiSpider(scrapy.Spider):
name = 'chouti'
allowed_domains = ['chouti.com']
start_urls = ['https://dig.chouti.com/']
def parse(self, response):
print(response.request.url)
# item_list = response.xpath('//div[@id="content-list"]/div[@class="item"]')
# for item in item_list:
# text = item.xpath('.//a/text()').extract_first()
# href = item.xpath('.//a/@href').extract_first()
page_list = response.xpath('//div[@id="dig_lcpage"]//a/@href').extract()
for page in page_list:
from scrapy.http import Request
page = "https://dig.chouti.com" + page
# yield Request(url=page,callback=self.parse,dont_filter=False) # https://dig.chouti.com/all/hot/recent/2
yield Request(url=page,callback=self.parse,dont_filter=True) # https://dig.chouti.com/all/hot/recent/2
注意：
- request_seen中编写正确逻辑
- dont_filter=False
深度
配置文件： # 限制深度 DEPTH_LIMIT = 3
cookie
方式一：
- 携带
Request(
url='https://dig.chouti.com/login',
method='POST',
body="phone=8613121758648&password=woshiniba&oneMonth=1",# # body=urlencode({})"phone=8615131255555&password=12sdf32sdf&oneMonth=1"
cookies=self.cookie_dict,
headers={
'Content-Type': 'application/x-www-form-urlencoded; charset=UTF-8'
},
callback=self.check_login
)
- 解析：
cookie_dict
cookie_jar = CookieJar()
cookie_jar.extract_cookies(response, response.request)
# 去对象中将cookie解析到字典
for k, v in cookie_jar._cookies.items():
for i, j in v.items():
for m, n in j.items():
cookie_dict[m] = n.value
start_url
内部原理
scrapy引擎来爬虫中取起始URL： 1. 调用start_requests并获取返回值 2. v = iter(返回值) 3. req1 = 执行 v.__next__() req2 = 执行 v.__next__() req3 = 执行 v.__next__() ... 4. req全部放到调度器中
编写
class ChoutiSpider(scrapy.Spider):
name = 'chouti'
allowed_domains = ['chouti.com']
start_urls = ['https://dig.chouti.com/']
cookie_dict = {}
def start_requests(self):
# 方式一：
for url in self.start_urls:
yield Request(url=url)
# 方式二：
# req_list = []
# for url in self.start_urls:
# req_list.append(Request(url=url))
# return req_list
定制：可以去redis获取
深度和优先级
深度
- 最开始是0 - 每次yield时，会根据原来请求中的depth + 1 配置：DEPTH_LIMIT 深度控制
优先级
- 请求被下载的优先级 -= 深度 * 配置 DEPTH_PRIORITY
配置：DEPTH_PRIORITY
下载中间件
scrapy中设置代理
内置
在爬虫启动时，提前在os.envrion中设置代理即可。
class ChoutiSpider(scrapy.Spider):
name = 'chouti'
allowed_domains = ['chouti.com']
start_urls = ['https://dig.chouti.com/']
cookie_dict = {}
def start_requests(self):
import os
os.environ['HTTPS_PROXY'] = "http://root:woshiniba@192.168.11.11:9999/"
os.environ['HTTP_PROXY'] = '19.11.2.32',
for url in self.start_urls:
yield Request(url=url,callback=self.parse)
meta（每次发请求都要自己携带）
class ChoutiSpider(scrapy.Spider):
name = 'chouti'
allowed_domains = ['chouti.com']
start_urls = ['https://dig.chouti.com/']
cookie_dict = {}
def start_requests(self):
for url in self.start_urls:
yield Request(url=url,callback=self.parse,meta={'proxy':'"http://root:woshiniba@192.168.11.11:9999/"'})
自定义
import base64 import random from six.moves.urllib.parse import unquote try: from urllib2 import _parse_proxy except ImportError: from urllib.request import _parse_proxy from six.moves.urllib.parse import urlunparse from scrapy.utils.python import to_bytes class XdbProxyMiddleware(object): def _basic_auth_header(self, username, password): user_pass = to_bytes( '%s:%s' % (unquote(username), unquote(password)), encoding='latin-1') return base64.b64encode(user_pass).strip() def process_request(self, request, spider): PROXIES = [ "http://root:woshiniba@192.168.11.11:9999/", "http://root:woshiniba@192.168.11.12:9999/", "http://root:woshiniba@192.168.11.13:9999/", "http://root:woshiniba@192.168.11.14:9999/", "http://root:woshiniba@192.168.11.15:9999/", "http://root:woshiniba@192.168.11.16:9999/", ] url = random.choice(PROXIES) orig_type = "" proxy_type, user, password, hostport = _parse_proxy(url) proxy_url = urlunparse((proxy_type or orig_type, hostport, '', '', '', '')) if user: creds = self._basic_auth_header(user, password) else: creds = None request.meta['proxy'] = proxy_url if creds: request.headers['Proxy-Authorization'] = b'Basic ' + creds
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