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。
听起来好像你真正要找的数据可以通过主页面上的一些javascript调用的辅助URL访问。
虽然您可以尝试在服务器上运行javascript来处理这个问题，但一种更简单的方法可能是使用Firefox加载页面，并使用Charles或Firebug之类的工具来准确识别辅助URL。然后，您可以直接查询该URL以获得您感兴趣的数据。
EDIT 2021年9月:phantomjs也不再维护
EDIT 30/Dec/2017:这个答案出现在谷歌搜索的顶部结果中，所以我决定更新它。老答案仍然在最后。
dryscape不再维护，开发人员推荐的库dryscape仅适用于Python 2。我发现使用Selenium的python库和Phantom JS作为web驱动程序足够快，也很容易完成工作。
一旦你安装了Phantom JS，确保phantomjs二进制文件在当前路径下可用:
phantomjs --version
# result:
2.1.1
#例子 为了给出一个例子，我用下面的HTML代码创建了一个示例页面。(链接):
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Javascript scraping test</title>
</head>
<body>
<p id='intro-text'>No javascript support</p>
<script>
document.getElementById('intro-text').innerHTML = 'Yay! Supports javascript';
</script>
</body>
</html>
没有javascript，它说:不支持javascript和javascript:耶!支持javascript
#抓取没有JS支持:
import requests
from bs4 import BeautifulSoup
response = requests.get(my_url)
soup = BeautifulSoup(response.text)
soup.find(id="intro-text")
# Result:
<p id="intro-text">No javascript support</p>
#抓取与JS支持:
from selenium import webdriver
driver = webdriver.PhantomJS()
driver.get(my_url)
p_element = driver.find_element_by_id(id_='intro-text')
print(p_element.text)
# result:
'Yay! Supports javascript'
你也可以使用Python库dryscraping来抓取javascript驱动的网站。
#抓取与JS支持:
import dryscrape
from bs4 import BeautifulSoup
session = dryscrape.Session()
session.visit(my_url)
response = session.body()
soup = BeautifulSoup(response)
soup.find(id="intro-text")
# Result:
<p id="intro-text">Yay! Supports javascript</p>
这似乎是一个很好的解决方案，从一个伟大的博客文章
import sys
from PyQt4.QtGui import *
from PyQt4.QtCore import *
from PyQt4.QtWebKit import *
from lxml import html
#Take this class for granted.Just use result of rendering.
class Render(QWebPage):
def __init__(self, url):
self.app = QApplication(sys.argv)
QWebPage.__init__(self)
self.loadFinished.connect(self._loadFinished)
self.mainFrame().load(QUrl(url))
self.app.exec_()
def _loadFinished(self, result):
self.frame = self.mainFrame()
self.app.quit()
url = 'http://pycoders.com/archive/'
r = Render(url)
result = r.frame.toHtml()
# This step is important.Converting QString to Ascii for lxml to process
# The following returns an lxml element tree
archive_links = html.fromstring(str(result.toAscii()))
print archive_links
# The following returns an array containing the URLs
raw_links = archive_links.xpath('//div[@class="campaign"]/a/@href')
print raw_links
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
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')
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.
Selenium是抓取JS和Ajax内容的最佳工具。
查看这篇文章，了解如何使用Python从web中提取数据
$ pip install selenium
然后下载Chrome webdriver。
from selenium import webdriver
browser = webdriver.Chrome()
browser.get("https://www.python.org/")
nav = browser.find_element_by_id("mainnav")
print(nav.text)
容易,对吧?
如果你以前曾经使用过python的Requests模块，我最近发现开发人员创建了一个名为Requests- html的新模块，现在它也有呈现JavaScript的能力。
你也可以访问https://html.python-requests.org/来了解更多关于这个模块的信息，或者如果你只对呈现JavaScript感兴趣，那么你可以访问https://html.python-requests.org/?#javascript-support来直接学习如何使用该模块使用Python来呈现JavaScript。
从本质上讲，一旦你正确安装了Requests-HTML模块，下面的例子，在上面的链接中显示，展示了你如何使用这个模块来抓取一个网站，并呈现网站中包含的JavaScript:
from requests_html import HTMLSession
session = HTMLSession()
r = session.get('http://python-requests.org/')
r.html.render()
r.html.search('Python 2 will retire in only {months} months!')['months']
'<time>25</time>' #This is the result.
我最近从YouTube上的一个视频中了解到这一点。点击这里!观看YouTube上演示该模块如何工作的视频。
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
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
我们没有得到正确的结果，因为任何javascript生成的内容都需要在DOM上呈现。当我们获取一个HTML页面时，我们获取初始的，未经javascript修改的DOM。
因此，我们需要在抓取页面之前呈现javascript内容。
由于selenium已经在本线程中多次提到(有时也提到了它的速度有多慢)，我将列出其他两种可能的解决方案。
解决方案1:这是一个关于如何使用Scrapy抓取javascript生成内容的非常好的教程，我们将遵循这一点。
我们需要:
Docker installed in our machine. This is a plus over other solutions until this point, as it utilizes an OS-independent platform. Install Splash following the instruction listed for our corresponding OS.Quoting from splash documentation: Splash is a javascript rendering service. It’s a lightweight web browser with an HTTP API, implemented in Python 3 using Twisted and QT5. Essentially we are going to use Splash to render Javascript generated content. Run the splash server: sudo docker run -p 8050:8050 scrapinghub/splash. Install the scrapy-splash plugin: pip install scrapy-splash Assuming that we already have a Scrapy project created (if not, let's make one), we will follow the guide and update the settings.py: Then go to your scrapy project’s settings.py and set these middlewares: DOWNLOADER_MIDDLEWARES = { 'scrapy_splash.SplashCookiesMiddleware': 723, 'scrapy_splash.SplashMiddleware': 725, 'scrapy.downloadermiddlewares.httpcompression.HttpCompressionMiddleware': 810, } The URL of the Splash server(if you’re using Win or OSX this should be the URL of the docker machine: How to get a Docker container's IP address from the host?): SPLASH_URL = 'http://localhost:8050' And finally you need to set these values too: DUPEFILTER_CLASS = 'scrapy_splash.SplashAwareDupeFilter' HTTPCACHE_STORAGE = 'scrapy_splash.SplashAwareFSCacheStorage' Finally, we can use a SplashRequest: In a normal spider you have Request objects which you can use to open URLs. If the page you want to open contains JS generated data you have to use SplashRequest(or SplashFormRequest) to render the page. Here’s a simple example: class MySpider(scrapy.Spider): name = "jsscraper" start_urls = ["http://quotes.toscrape.com/js/"] def start_requests(self): for url in self.start_urls: yield SplashRequest( url=url, callback=self.parse, endpoint='render.html' ) def parse(self, response): for q in response.css("div.quote"): quote = QuoteItem() quote["author"] = q.css(".author::text").extract_first() quote["quote"] = q.css(".text::text").extract_first() yield quote SplashRequest renders the URL as html and returns the response which you can use in the callback(parse) method.
解决方案2:我们暂且称之为实验性的(2018年5月)…… 此解决方案仅适用于Python版本3.6(目前)。
你知道请求模块吗(谁不知道呢)? 现在它有了一个网络爬行的小兄弟:requests-HTML:
这个库旨在使解析HTML(例如抓取网页)尽可能简单和直观。
安装请求-html: pipenv 对页面的url进行请求: 导入HTMLSession 会话= HTMLSession() R = session.get(a_page_url) 渲染响应以获得Javascript生成的比特: r.html.render ()
最后，该模块似乎提供了抓取功能。 或者，我们也可以尝试使用我们刚刚渲染的r.html对象来使用BeautifulSoup。
使用PyQt5
from PyQt5.QtWidgets import QApplication
from PyQt5.QtCore import QUrl
from PyQt5.QtWebEngineWidgets import QWebEnginePage
import sys
import bs4 as bs
import urllib.request
class Client(QWebEnginePage):
def __init__(self,url):
global app
self.app = QApplication(sys.argv)
QWebEnginePage.__init__(self)
self.html = ""
self.loadFinished.connect(self.on_load_finished)
self.load(QUrl(url))
self.app.exec_()
def on_load_finished(self):
self.html = self.toHtml(self.Callable)
print("Load Finished")
def Callable(self,data):
self.html = data
self.app.quit()
# url = ""
# client_response = Client(url)
# print(client_response.html)
如前所述，Selenium是呈现JavaScript结果的好选择:
from selenium.webdriver import Firefox
from selenium.webdriver.firefox.options import Options
options = Options()
options.headless = True
browser = Firefox(executable_path="/usr/local/bin/geckodriver", options=options)
url = "https://www.example.com"
browser.get(url)
gazpacho是一个非常容易解析渲染html的库:
from gazpacho import Soup
soup = Soup(browser.page_source)
soup.find("a").attrs['href']
我最近使用requests_html库来解决这个问题。
他们的扩展文档在readthedocs。IO非常好(跳过pypi.org上的带注释的版本)。如果您的用例是基本的，那么您可能会取得一些成功。
from requests_html import HTMLSession
session = HTMLSession()
response = session.request(method="get",url="www.google.com/")
response.html.render()
如果你在使用response.html.render()呈现你需要的数据时遇到麻烦，你可以将一些javascript传递给呈现函数来呈现你需要的特定js对象。这是从他们的文档中复制的，但这可能正是你需要的:
如果指定了script，它将在 运行时。例子:
script = """
() => {
return {
width: document.documentElement.clientWidth,
height: document.documentElement.clientHeight,
deviceScaleFactor: window.devicePixelRatio,
}
}
"""
返回执行脚本的返回值，如果有的话:
>>> response.html.render(script=script)
{'width': 800, 'height': 600, 'deviceScaleFactor': 1}
In my case, the data I wanted were the arrays that populated a javascript plot but the data wasn't getting rendered as text anywhere in the html. Sometimes its not clear at all what the object names are of the data you want if the data is populated dynamically. If you can't track down the js objects directly from view source or inspect, you can type in "window" followed by ENTER in the debugger console in the browser (Chrome) to pull up a full list of objects rendered by the browser. If you make a few educated guesses about where the data is stored, you might have some luck finding it there. My graph data was under window.view.data in the console, so in the "script" variable passed to the .render() method quoted above, I used:
return {
data: window.view.data
}
尝试直接访问API
在抓取中常见的场景是网页从API端点异步请求数据。一个最小的例子是以下网站:
身体< > < >脚本 fetch(“https://jsonplaceholder.typicode.com/posts/1”) .then(res => { if (!res.ok)抛出错误(res.status); 返回res.json (); }) .then(data => { //页面加载后通过JS动态注入数据 document.body.innerText = data.title; }) .catch(err => console.error(err)) ； > < /脚本 身体< / >
在许多情况下，API将受到CORS或访问令牌的保护，或速率限制过高，但在其他情况下，它是公开可访问的，您可以完全绕过网站。对于CORS问题，你可以在任何地方尝试CORS。
一般的过程是使用浏览器的开发人员工具的网络选项卡来搜索页面发出的请求，以获得您想要抓取的数据的关键字/子字符串。通常，您会看到一个不受保护的API请求端点，该端点带有一个JSON有效负载，您可以直接使用urllib或请求模块访问该有效负载。上面的可运行代码片段就是这种情况，你可以用它来练习。点击“运行片段”后，下面是我如何在我的网络选项卡中找到端点:
这个例子是虚构的;从静态标记来看，端点URL可能不明显，因为它可以被动态组装、缩小并隐藏在数十个其他请求和端点之下。网络请求还将显示任何相关的请求有效负载细节，例如您可能需要的访问令牌。
在获取端点URL和相关细节后，使用标准HTTP库在Python中构建一个请求并请求数据:
>>> import requests
>>> res = requests.get("https://jsonplaceholder.typicode.com/posts/1")
>>> data = res.json()
>>> data["title"]
'sunt aut facere repellat provident occaecati excepturi optio reprehenderit'
当你可以摆脱它时，这往往比使用Selenium、Pyppeteer、Scrapy或其他流行的抓取库更容易、更快、更可靠。
如果您很不幸，数据没有通过API请求以良好的格式返回数据，那么它可能是原始浏览器负载的一部分，在<script>标记中，作为JSON字符串或(更可能的是)JS对象。例如:
<body> <script> var someHardcodedData = { 用户 ID： 1， 编号： 1， 题目： “Sunt aut facere repellat provident occaecati excepturi optio reprehenderit”， Body： 'quia et suscipit\nsuscipit recusandae con sequuntur expedita et\nreprehenderit molestiae ut ut quas totam\nnostrum rerum est autem sunt rem eveniet architecto' }; document.body.textContent = someHardcodedData.title; </script> </body>
没有一种万能的方法来获取这些数据。基本技术是使用BeautifulSoup访问<script>标记文本，然后应用正则表达式或解析来提取对象结构、JSON字符串或数据可能采用的任何格式。下面是上面所示的示例结构的概念证明:
import json
import re
from bs4 import BeautifulSoup
# pretend we've already used requests to retrieve the data,
# so we hardcode it for the purposes of this example
text = """
<body>
<script>
var someHardcodedData = {
userId: 1,
id: 1,
title: 'sunt aut facere repellat provident occaecati excepturi optio reprehenderit',
body: 'quia et suscipit\nsuscipit recusandae con sequuntur expedita et cum\nreprehenderit molestiae ut ut quas totam\nnostrum rerum est autem sunt rem eveniet architecto'
};
document.body.textContent = someHardcodedData.title;
</script>
</body>
"""
soup = BeautifulSoup(text, "lxml")
script_text = str(soup.select_one("script"))
pattern = r"title: '(.*?)'"
print(re.search(pattern, script_text, re.S).group(1))
看看下面这些解析JS对象的资源，它们不是很有效的JSON:
如何将原始javascript对象转换为python字典? 如何修复JSON键值没有双引号?
以下是一些使用API绕过抓取的额外案例研究/概念证明:
如何使用Python beautifulsoup将yelp评论和星级评分刮到CSV Beautiful Soup对现有元素返回None 从BeautifulSoup Python中提取数据 通过POST收集Bandcamp粉丝(使用一种混合方法，即向网站发出初始请求，从使用BeautifulSoup的标记中提取一个令牌，然后在对JSON端点的第二个请求中使用)
如果所有这些都失败了，请尝试本线程中列出的许多动态抓取库中的一个。
Pyppeteer
你可以考虑Pyppeteer，它是Chrome/Chromium驱动程序前端的Python移植版本。
下面是一个简单的例子，展示了如何使用pyppeterer动态地访问被注入到页面中的数据:
import asyncio
from pyppeteer import launch
async def main():
browser = await launch({"headless": True})
[page] = await browser.pages()
# normally, you go to a live site...
#await page.goto("http://www.example.com")
# but for this example, just set the HTML directly:
await page.setContent("""
<body>
<script>
// inject content dynamically with JS, not part of the static HTML!
document.body.innerHTML = `<p>hello world</p>`;
</script>
</body>
""")
print(await page.content()) # shows that the `<p>` was inserted
# evaluate a JS expression in browser context and scrape the data
expr = "document.querySelector('p').textContent"
print(await page.evaluate(expr, force_expr=True)) # => hello world
await browser.close()
asyncio.get_event_loop().run_until_complete(main())
请参阅pyppeterer的参考文档。
简单快捷的解决方案:
我也遇到过同样的问题。我想刮一些数据是用JavaScript构建的。如果我只用BeautifulSoup从这个网站抓取文本，那么我就以文本中的标签结束。 我想渲染这个标签，并将从中抓取信息。 另外，我不想使用像Scrapy和selenium这样的笨重框架。
我发现请求模块的get方法接受url，它实际上呈现脚本标签。
例子:
import requests
custom_User_agent = "Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:47.0) Gecko/20100101 Firefox/47.0"
url = "https://www.abc.xyz/your/url"
response = requests.get(url, headers={"User-Agent": custom_User_agent})
html_text = response.text
这将呈现加载站点和呈现标签。
希望这将有助于作为快速和简单的解决方案，渲染网站加载脚本标签。
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()
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