Scrapy框架介绍之Puppeteer渲染
1、Scrapy框架Scrapy是用纯Python实现一个为了爬取网站数据、提取结构性数据而编写的应用框架，用途非常广泛。
框架的力量，用户只需要定制开发几个模块就可以轻松的实现一个爬虫，用来抓取网页内容以及各种图片，非常之方便。
Scrapy 使用了 Twisted'twɪstɪd异步网络框架来处理网络通讯，可以加快我们的下载速度，不用自己去实现异步框架，并且包含了各种中间件接口，可以灵活的完成各种需求。
https://cdn.nlark.com/yuque/0/2020/jpeg/1313142/1590567182769-50d3621e-51e1-4bd4-a3af-057b3013d5be.jpeg?x-oss-process=image%2Fwatermark%2Ctype_d3F5LW1pY3JvaGVp%2Csize_10%2Ctext_5Lq_54mb5LqRIHd3dy4xNnl1bi5jbg%3D%3D%2Ccolor_FFFFFF%2Cshadow_50%2Ct_80%2Cg_se%2Cx_10%2Cy_10
Scrapy Engine(引擎): 负责Spider、ItemPipeline、Downloader、Scheduler中间的通讯，信号、数据传递等。
Scheduler(调度器): 它负责接受引擎发送过来的Request请求，并按照一定的方式进行整理排列，入队，当引擎需要时，交还给引擎。
Downloader（下载器）：负责下载Scrapy Engine(引擎)发送的所有Requests请求，并将其获取到的Responses交还给Scrapy Engine(引擎)，由引擎交给Spider来处理，
Spider（爬虫）：它负责处理所有Responses,从中分析提取数据，获取Item字段需要的数据，并将需要跟进的URL提交给引擎，再次进入Scheduler(调度器)，
Item Pipeline(管道)：它负责处理Spider中获取到的Item，并进行进行后期处理（详细分析、过滤、存储等）的地方.
Downloader Middlewares（下载中间件）：你可以当作是一个可以自定义扩展下载功能的组件。
Spider Middlewares（Spider中间件）：你可以理解为是一个可以自定扩展和操作引擎和Spider中间通信的功能组件（比如进入Spider的Responses;和从Spider出去的Requests）
2、Puppeteer渲染
Puppeteer 是 Chrome 开发团队在 2017 年发布的一个 Node.js 包，用来模拟 Chrome 浏览器的运行。
为了爬取js渲染的html页面，我们需要用浏览器来解析js后生成html。在scrapy中可以利用pyppeteer来实现对应功能。
完整代码 📎scrapy-pyppeteer.zip
我们需要新建项目中middlewares.py文件(./项目名/middlewares.py)
import websockets
from scrapy.http import HtmlResponse
from logging import getLogger
import asyncio
import pyppeteer
import logging
from concurrent.futures._base import TimeoutError
import base64
import sys
import random
pyppeteer_level = logging.WARNING
logging.getLogger('websockets.protocol').setLevel(pyppeteer_level)
logging.getLogger('pyppeteer').setLevel(pyppeteer_level)
PY3 = sys.version_info >= 3
def base64ify(bytes_or_str):
if PY3 and isinstance(bytes_or_str, str):
input_bytes = bytes_or_str.encode('utf8')
else:
input_bytes = bytes_or_str
output_bytes = base64.urlsafe_b64encode(input_bytes)
if PY3:
return output_bytes.decode('ascii')
else:
return output_bytes
class ProxyMiddleware(object):
USER_AGENT = open('useragents.txt').readlines()
def process_request(self, request, spider):
# 代理服务器
proxyHost = "t.16yun.cn"
proxyPort = "31111"
# 代理隧道验证信息
proxyUser = "username"
proxyPass = "password"
request.meta['proxy'] = "http://{0}:{1}".format(proxyHost, proxyPort)
# 添加验证头
encoded_user_pass = base64ify(proxyUser + ":" + proxyPass)
request.headers['Proxy-Authorization'] = 'Basic ' + encoded_user_pass
# 设置IP切换头(根据需求)
tunnel = random.randint(1, 10000)
request.headers['Proxy-Tunnel'] = str(tunnel)
request.headers['User-Agent'] = random.choice(self.USER_AGENT)
class PyppeteerMiddleware(object):
def __init__(self, **args):
"""
init logger, loop, browser
:param args:
"""
self.logger = getLogger(__name__)
self.loop = asyncio.get_event_loop()
self.browser = self.loop.run_until_complete(
pyppeteer.launch(headless=True))
self.args = args
def __del__(self):
"""
close loop
:return:
"""
self.loop.close()
def render(self, url, retries=1, script=None, wait=0.3, scrolldown=False, sleep=0,
timeout=8.0, keep_page=False):
"""
render page with pyppeteer
:param url: page url
:param retries: max retry times
:param script: js script to evaluate
:param wait: number of seconds to wait before loading the page, preventing timeouts
:param scrolldown: how many times to page down
:param sleep: how many long to sleep after initial render
:param timeout: the longest wait time, otherwise raise timeout error
:param keep_page: keep page not to be closed, browser object needed
:param browser: pyppetter browser object
:param with_result: return with js evaluation result
:return: content,
"""
# define async render
async def async_render(url, script, scrolldown, sleep, wait, timeout, keep_page):
try:
# basic render
page = await self.browser.newPage()
await asyncio.sleep(wait)
response = await page.goto(url, options={'timeout': int(timeout * 1000)})
if response.status != 200:
return None, None, response.status
result = None
# evaluate with script
if script:
result = await page.evaluate(script)
# scroll down for {scrolldown} times
if scrolldown:
for _ in range(scrolldown):
await page._keyboard.down('PageDown')
await asyncio.sleep(sleep)
else:
await asyncio.sleep(sleep)
if scrolldown:
await page._keyboard.up('PageDown')
# get html of page
content = await page.content()
return content, result, response.status
except TimeoutError:
return None, None, 500
finally:
# if keep page, do not close it
if not keep_page:
await page.close()
content, result, status = * 3
# retry for {retries} times
for i in range(retries):
if not content:
content, result, status = self.loop.run_until_complete(
async_render(url=url, script=script, sleep=sleep, wait=wait,
scrolldown=scrolldown, timeout=timeout, keep_page=keep_page))
else:
break
# if need to return js evaluation result
return content, result, status
def process_request(self, request, spider):
"""
:param request: request object
:param spider: spider object
:return: HtmlResponse
"""
if request.meta.get('render'):
try:
self.logger.debug('rendering %s', request.url)
html, result, status = self.render(request.url)
return HtmlResponse(url=request.url, body=html, request=request, encoding='utf-8',
status=status)
except websockets.exceptions.ConnectionClosed:
pass
@classmethod
def from_crawler(cls, crawler):
return cls(**crawler.settings.get('PYPPETEER_ARGS', {}))
然后修改项目配置文件 (./项目名/settings.py)
DOWNLOADER_MIDDLEWARES = {
'scrapypyppeteer.middlewares.PyppeteerMiddleware': 543,
'scrapypyppeteer.middlewares.ProxyMiddleware': 100,
}
然后我们运行程序
https://cdn.nlark.com/yuque/0/2020/png/1313084/1589263259438-dc052a4e-d968-4fda-bd6a-ee435e65e06c.png?x-oss-process=image%2Fresize%2Cw_436
页:
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