How to fetch complete webpage (using javascript) in python - javascript

I'm trying to use urllib2 to fetch webpage from a website. After I managed to log on and retrieve the page, I found out the page has some <script>.....</script> inside. How can I save the rendered the output (the complete content of the webpage, not the script)?

Javascript can't be easily handled if you are using urllib.
What you need is a headless browser, for ex. WebKit.
A simple example can be found here.
If you don't want yourself to be limited to python, try Phantomjs

I'd also like to mention pywebkitgtk (which I've been using a lot lately as an embedded browser), and Selenium.

Related

How can I screen scrape a multi page application using javascript?

How can I screen scrape a multi page application? I want to do this using Javascript. Here are the approaches I have considered and the problems I have encountered.
Using the Fetch web API in a Node application to get the web pages
Problem: The web pages won't load properly when being fetched. I guess all javascript on the page does not run when the page is fetched.
Running JavaScript from the console
This is a very simple way to inject JavaScript straight into the document. But one problem is that opening the web page is a browser and pasting into the console is manual work. Another problem is that while this works for single page application it becomes very cumbersome for multi-page applications.
What better approach exists that solves the problems I have encountered?
Depends on what are you doing. If you just want to get some that from some website then injecting JS in the page is the way to go.
But as you said it's manual work from which I deduce you want to scrape the sites and save the data maybe. In this case a service side script is better suited. To fix the problem with the JavaScript not being loaded you can use things like PhantomJs or Horseman.
Take a look at this: https://medium.com/#designman/building-a-performant-web-scraper-in-node-js-5f4449674163
If you want to save website content (html, js, css files, images) to file system you can take a look on website-scraper package for nodejs https://www.npmjs.com/package/website-scraper
It also has plugin for PhantomJS which allows to handle single page applications

Rendering HTML local file with out browser or networking (lightweight)

I have had a lot of trouble trying to find information or possible examples of this being done.
I would like to render html in a window and take the js from the html and output that to a python code.
The Html is local and there will never be an internet connection for it to run off. Everythin i try shearch for possible answers everyone always seems to relate back to using some small lightweigh browser which in my case isn't an option to use.
Fort some more detail, I am running Selenium-Webdriver
(python) and Iceweasel(Raspberry Pi B+) to get the value of a element from a html page. So using a different browser isnt possible as the lightweight ones are not compatible with selenium. Using Selenium and Iceweasel takes in excess of 2 miunets to fully load up which for what i need it for is far to long.
I had a look into Awesomium but i think it lacks compatability with the Raspberry Pi.
My other thought was to use OpenGL to render the html but found no easy explained examples.
Currently looking into LibRocket, Berkelium and QWebView but again i dont think they will have anythin i need with the compatability i need.
EDIT:
Basically i want a Canvas capeable of rendering HTML to a screen using X11. On the HTML there will be buttons. I want those buttons to preform actions inside a python script.
The way i see it, a browser is basically a toolbar, a canvas and a lot of networking. I want to strip away as much of that as possible and just remain with the canvas.
First go to the directory that you has the local webpage. Than run python -m SimpleHTTPServer 8000. This will "render the html" in a window. Then view source and paste the javascript into a python file. Alternatively if you would like to automate piping the javascript into an out file you can use beautiful soup to select the javascript and write it to any file you want. Then manipulate it in python however you want.

Scraping a dynamically loaded, javascript lidded website using Pythons BeautifulSoup [duplicate]

I need to scrape a site with python. I obtain the source html code with the urlib module, but I need to scrape also some html code that is generated by a javascript function (which is included in the html source). What this functions does "in" the site is that when you press a button it outputs some html code. How can I "press" this button with python code? Can scrapy help me? I captured the POST request with firebug but when I try to pass it on the url I get a 403 error. Any suggestions?
In Python, I think Selenium 1.0 is the way to go. It’s a library that allows you to control a real web browser from your language of choice.
You need to have the web browser in question installed on the machine your script runs on, but it looks like the most reliable way to programmatically interrogate websites that use a lot of JavaScript.
Since there is no comprehensive answer here, I'll go ahead and write one.
To scrape off JS rendered pages, we will need a browser that has a JavaScript engine (e.i, support JavaScript rendering)
Options like Mechanize, url2lib will not work since they DO NOT support JavaScript.
So here's what you do:
Setup PhantomJS to run with Selenium. After installing the dependencies for both of them (refer this), you can use the following code as an example to fetch the fully rendered website.
from selenium import webdriver
driver = webdriver.PhantomJS()
driver.get('http://jokes.cc.com/')
soupFromJokesCC = BeautifulSoup(driver.page_source) #page_source fetches page after rendering is complete
driver.save_screenshot('screen.png') # save a screenshot to disk
driver.quit()
I have had to do this before (in .NET) and you are basically going to have to host a browser, get it to click the button, and then interrogate the DOM (document object model) of the browser to get at the generated HTML.
This is definitely one of the downsides to web apps moving towards an Ajax/Javascript approach to generating HTML client-side.
I use webkit, which is the browser renderer behind Chrome and Safari. There are Python bindings to webkit through Qt. And here is a full example to execute JavaScript and extract the final HTML.
For Scrapy (great python scraping framework) there is scrapyjs: an additional downloader handler / middleware handler able to scraping javascript generated content.
It's based on webkit engine by pygtk, python-webkit, and python-jswebkit and it's quite simple.

How to get the source code of webbrowser with python

I am writing a spider with scrapy, however, I come across some website which rendered with js, thus the urllib2.open_url does not work. I have found that I could open the browser with webbrowser.open_new(url), however, I did not find how to get the src code of page with webbrowser. Are there any way that I could use to do this with webbrowser, or are there any other solutions without webbrowser to deal with the js sites?
You can use scraper with Webkit engine available out there.
One of them is dryscrape.
Example:
import dryscrape
search_term = 'dryscrape'
# set up a web scraping session
sess = dryscrape.Session(base_url = 'http://google.com')
# we don't need images
sess.set_attribute('auto_load_images', False)
# visit homepage and search for a term
sess.visit('/')
q = sess.at_xpath('//*[#name="q"]')
q.set(search_term)
q.form().submit()
# extract all links
for link in sess.xpath('//a[#href]'):
print link['href']
# save a screenshot of the web page
sess.render('google.png')
print "Screenshot written to 'google.png'"
See more info at:
https://github.com/niklasb/dryscrape
https://dryscrape.readthedocs.org/en/latest/index.html
If you need a full js engine, there are a number of ways you can drive webkit from Python. Until recently, these sort of things were done with Selenium. Selenium drives an entire browser.
More recently there are newer and simpler ways to run a webkit engine (which includes the v8 javascript engine) from Python. See this SO question:
Headless Browser for Python (Javascript support REQUIRED!)
It references this blog as an example Scraping Javascript Webpages with Webkit . It looks to do more or less just what you need.
I'm trying to find an answer to the same problem for a few days now.
I suggest you try QT framework with WebKit.
There are two python bindings. One is PyQt and the other one is PySide. You can use them directly if you want to create something more complex or you want to have 100% control over your code.
For trivial stuff like executing JavaScript in a browser environment you can use Ghost.py. It has some sort of documentation and some problems when using it from the command line but otherwise it's just great.
If you need to process JavaScript you'll need to implement a JavaScript engine. This makes your spider much more complex. Mainly because JavaScript almost always modifies the DOM based on time or an action taken by the user. This makes it extremely challenging to process JS in a crawler.
If you really need to process JavaScript in your spider you can have a look at the JavaScript engine by Mozilla: https://developer.mozilla.org/en/docs/SpiderMonkey

How can I get dynamically web content using Perl?

This is kind of tricky. There is this webpage which, I am guessing, uses some kind of AJAX to pull out content based on the search query. When I fetch the page using get in Perl, it fetches the script code behind the php/html, but not the results which are displayed when the query is searched manually. I need to be able to fetch the content of the results page. Is there anyway to do this in Perl?
Take a look at Selenium RC and the WWW::Selenium module in Perl. With them you can control a real web browser.
Another option is WWW::HtmlUnit which uses the HtmlUnit Java library to execute the JavaScript without a web browser. WWW::HtmlUnit uses Inline::Java to give Perl access to the library. I have found that when installing, it is best to say No to the question "Do you wish to build the JNI extension?".
If you are writing tests that need to check the rendered page, you can have a look at Schwern's javascript-tap-harness, which works with Selenium and handles all the scaffolding.
I also found Using WWW::Selenium To Test Or Automate An Ajax Website pretty useful.

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