我试图开发一个简单的网页刮板。我想提取没有HTML代码的文本。它适用于普通HTML,但不适用于JavaScript代码添加文本的某些页面。
例如,如果一些JavaScript代码添加了一些文本,我不能看到它,因为当我调用:
response = urllib2.urlopen(request)
我得到了原始文本而没有添加的文本(因为JavaScript是在客户端执行的)。
所以,我正在寻找一些解决这个问题的想法。
我试图开发一个简单的网页刮板。我想提取没有HTML代码的文本。它适用于普通HTML,但不适用于JavaScript代码添加文本的某些页面。
例如,如果一些JavaScript代码添加了一些文本,我不能看到它,因为当我调用:
response = urllib2.urlopen(request)
我得到了原始文本而没有添加的文本(因为JavaScript是在客户端执行的)。
所以,我正在寻找一些解决这个问题的想法。
当前回答
把BeautifulSoup和Selenium混合在一起对我来说效果很好。
from selenium import webdriver
from selenium.webdriver.common.by import By
from selenium.webdriver.support.ui import WebDriverWait
from selenium.webdriver.support import expected_conditions as EC
from bs4 import BeautifulSoup as bs
driver = webdriver.Firefox()
driver.get("http://somedomain/url_that_delays_loading")
try:
element = WebDriverWait(driver, 10).until(
EC.presence_of_element_located((By.ID, "myDynamicElement"))) #waits 10 seconds until element is located. Can have other wait conditions such as visibility_of_element_located or text_to_be_present_in_element
html = driver.page_source
soup = bs(html, "lxml")
dynamic_text = soup.find_all("p", {"class":"class_name"}) #or other attributes, optional
else:
print("Couldnt locate element")
附注:你可以在这里找到更多的等待条件
其他回答
You'll want to use urllib, requests, beautifulSoup and selenium web driver in your script for different parts of the page, (to name a few). Sometimes you'll get what you need with just one of these modules. Sometimes you'll need two, three, or all of these modules. Sometimes you'll need to switch off the js on your browser. Sometimes you'll need header info in your script. No websites can be scraped the same way and no website can be scraped in the same way forever without having to modify your crawler, usually after a few months. But they can all be scraped! Where there's a will there's a way for sure. If you need scraped data continuously into the future just scrape everything you need and store it in .dat files with pickle. Just keep searching how to try what with these modules and copying and pasting your errors into the Google.
Playwright-Python
还有一种选择是剧作家- Python,它是微软剧作家(本身是受木偶大师影响的浏览器自动化库)到Python的移植。
下面是选择一个元素并抓取它的文本的最小示例:
from playwright.sync_api import sync_playwright
with sync_playwright() as p:
browser = p.chromium.launch()
page = browser.new_page()
page.goto("http://whatsmyuseragent.org/")
ua = page.query_selector(".user-agent");
print(ua.text_content())
browser.close()
我个人更喜欢在单独的容器中使用scrapy和selenium和dockerizing。通过这种方式,你既可以轻松安装,也可以抓取几乎所有包含某种形式javascript的现代网站。这里有一个例子:
使用scrapy startproject创建你的scraper并编写你的蜘蛛,骨架可以像这样简单:
import scrapy
class MySpider(scrapy.Spider):
name = 'my_spider'
start_urls = ['https://somewhere.com']
def start_requests(self):
yield scrapy.Request(url=self.start_urls[0])
def parse(self, response):
# do stuff with results, scrape items etc.
# now were just checking everything worked
print(response.body)
真正的魔力发生在middleware .py中。重写下载中间件中的两个方法__init__和process_request,方法如下:
# import some additional modules that we need
import os
from copy import deepcopy
from time import sleep
from scrapy import signals
from scrapy.http import HtmlResponse
from selenium import webdriver
class SampleProjectDownloaderMiddleware(object):
def __init__(self):
SELENIUM_LOCATION = os.environ.get('SELENIUM_LOCATION', 'NOT_HERE')
SELENIUM_URL = f'http://{SELENIUM_LOCATION}:4444/wd/hub'
chrome_options = webdriver.ChromeOptions()
# chrome_options.add_experimental_option("mobileEmulation", mobile_emulation)
self.driver = webdriver.Remote(command_executor=SELENIUM_URL,
desired_capabilities=chrome_options.to_capabilities())
def process_request(self, request, spider):
self.driver.get(request.url)
# sleep a bit so the page has time to load
# or monitor items on page to continue as soon as page ready
sleep(4)
# if you need to manipulate the page content like clicking and scrolling, you do it here
# self.driver.find_element_by_css_selector('.my-class').click()
# you only need the now properly and completely rendered html from your page to get results
body = deepcopy(self.driver.page_source)
# copy the current url in case of redirects
url = deepcopy(self.driver.current_url)
return HtmlResponse(url, body=body, encoding='utf-8', request=request)
不要忘记在settings.py文件中取消下一行的注释来启用这个中间件:
DOWNLOADER_MIDDLEWARES = {
'sample_project.middlewares.SampleProjectDownloaderMiddleware': 543,}
接下来是dockerization。从一个轻量级映像创建Dockerfile(我在这里使用python Alpine),复制你的项目目录到它,安装要求:
# Use an official Python runtime as a parent image
FROM python:3.6-alpine
# install some packages necessary to scrapy and then curl because it's handy for debugging
RUN apk --update add linux-headers libffi-dev openssl-dev build-base libxslt-dev libxml2-dev curl python-dev
WORKDIR /my_scraper
ADD requirements.txt /my_scraper/
RUN pip install -r requirements.txt
ADD . /scrapers
最后在docker-compose.yaml中把所有这些都整合在一起:
version: '2'
services:
selenium:
image: selenium/standalone-chrome
ports:
- "4444:4444"
shm_size: 1G
my_scraper:
build: .
depends_on:
- "selenium"
environment:
- SELENIUM_LOCATION=samplecrawler_selenium_1
volumes:
- .:/my_scraper
# use this command to keep the container running
command: tail -f /dev/null
运行docker-compose up -d。如果你是第一次这样做,它将需要一段时间来获取最新的硒/独立铬和构建你的刮刀图像以及。
完成后,您可以检查容器是否使用docker ps运行,还可以检查selenium容器的名称是否与传递给scraper容器的环境变量的名称相匹配(在这里,它是SELENIUM_LOCATION=samplecrawler_selenium_1)。
使用docker exec -ti YOUR_CONTAINER_NAME sh进入你的刮板容器,我的命令是docker exec -ti samplecrawler_my_scraper_1 sh, cd到正确的目录下,并用scrapy爬行my_spider运行你的刮板。
所有内容都在我的github页面上,你可以从这里获取
你也可以使用webdriver执行javascript。
from selenium import webdriver
driver = webdriver.Firefox()
driver.get(url)
driver.execute_script('document.title')
或者将值存储在变量中
result = driver.execute_script('var text = document.title ; return text')
也许硒可以做到。
from selenium import webdriver
import time
driver = webdriver.Firefox()
driver.get(url)
time.sleep(5)
htmlSource = driver.page_source