I'd like to use Python to scrape the contents of the "Were you looking for these authors:" box on web pages like this one: http://academic.research.microsoft.com/Search?query=lander
Unfortunately the contents of the box get loaded dynamically by JavaScript. Usually in this situation I can read the Javascript to figure out what's going on, or I can use an browser extension like Firebug to figure out where the dynamic content is coming from. No such luck this time...the Javascript is pretty convoluted and Firebug doesn't give many clues about how to get at the content.
Are there any tricks that will make this task easy?
Instead of trying to reverse engineer it, you can use ghost.py to directly interact with JavaScript on the page.
If you run the following query in a chrome console, you'll see it returns everything you want.
document.getElementsByClassName('inline-text-org');
Returns
[<div class="inline-text-org" title="University of Manchester">University of Manchester</div>,
<div class="inline-text-org" title="University of California Irvine">University of California ...</div>
etc...
You can run JavaScript through python in a real life DOM using ghost.py.
This is really cool:
from ghost import Ghost
ghost = Ghost()
page, resources = ghost.open('http://academic.research.microsoft.com/Search?query=lander')
result, resources = ghost.evaluate(
"document.getElementsByClassName('inline-text-org');")
A very similar question was asked earlier here.
Quoted is selenium, originally a testing environment for web-apps.
I usually use Chrome's Developer Mode, which IMHO already gives even more details than Firefox.
For scraping dynamic content, you need not a simple scraper but a full-fledged headless browser.
dhamaniasad/HeadlessBrowsers: A list of (almost) all headless web browsers in existence is the fullest list of these that I've seen; it lists which languages each has bindings for.
(Note that more than a few of the listed projects are abandoned!)
Related
This question already has answers here:
Web-scraping JavaScript page with Python
(18 answers)
Closed 6 hours ago.
What is the best method to scrape a dynamic website where most of the content is generated by what appears to be ajax requests? I have previous experience with a Mechanize, BeautifulSoup, and python combo, but I am up for something new.
--Edit--
For more detail: I'm trying to scrape the CNN primary database. There is a wealth of information there, but there doesn't appear to be an api.
The best solution that I found was to use Firebug to monitor XmlHttpRequests, and then to use a script to resend them.
This is a difficult problem because you either have to reverse engineer the JavaScript on a per-site basis, or implement a JavaScript engine and run the scripts (which has its own difficulties and pitfalls).
It's a heavy weight solution, but I've seen people doing this with GreaseMonkey scripts - allow Firefox to render everything and run the JavaScript, and then scrape the elements. You can even initiate user actions on the page if needed.
Selenium IDE, a tool for testing, is something I've used for a lot of screen-scraping. There are a few things it doesn't handle well (Javascript window.alert() and popup windows in general), but it does its work on a page by actually triggering the click events and typing into the text boxes. Because the IDE portion runs in Firefox, you don't have to do all of the management of sessions, etc. as Firefox takes care of it. The IDE records and plays tests back.
It also exports C#, PHP, Java, etc. code to build compiled tests/scrapers that are executed on the Selenium server. I've done that for more than a few of my Selenium scripts, which makes things like storing the scraped data in a database much easier.
Scripts are fairly simple to write and alter, being made up of things like ("clickAndWait","submitButton"). Worth a look given what you're describing.
Adam Davis's advice is solid.
I would additionally suggest that you try to "reverse-engineer" what the JavaScript is doing, and instead of trying to scrape the page, you issue the HTTP requests that the JavaScript is issuing and interpret the results yourself (most likely in JSON format, nice and easy to parse). This strategy could be anything from trivial to a total nightmare, depending on the complexity of the JavaScript.
The best possibility, of course, would be to convince the website's maintainers to implement a developer-friendly API. All the cool kids are doing it these days 8-) Of course, they might not want their data scraped in an automated fashion... in which case you can expect a cat-and-mouse game of making their page increasingly difficult to scrape :-(
There is a bit of a learning curve, but tools like Pamie (Python) or Watir (Ruby) will let you latch into the IE web browser and get at the elements. This turns out to be easier than Mechanize and other HTTP level tools since you don't have to emulate the browser, you just ask the browser for the html elements. And it's going to be way easier than reverse engineering the Javascript/Ajax calls. If needed you can also use tools like beatiful soup in conjunction with Pamie.
Probably the easiest way is to use IE webbrowser control in C# (or any other language). You have access to all the stuff inside browser out of the box + you dont need to care about cookies, SSL and so on.
i found the IE Webbrowser control have all kinds of quirks and workarounds that would justify some high quality software to take care of all those inconsistencies, layered around the shvwdoc.dll api and mshtml and provide a framework.
This seems like it's a pretty common problem. I wonder why someone hasn't anyone developed a programmatic browser? I'm envisioning a Firefox you can call from the command line with a URL as an argument and it will load the page, run all of the initial page load JS events and save the resulting file.
I mean Firefox, and other browsers already do this, why can't we simply strip off the UI stuff?
I am looking for a python module that will let me navigate searchbars, links etc of a website.
For context I am looking to do a little webscraping of this website [https://www.realclearpolitics.com/]
I simply want to take information on each state (polling data etc) in relation to the 2020 election and organize it all in a collection of a database.
Obviously there are a lot of states to go through and each is on a seperate webpage. So im looking for a method in python in which i could quickly navigate the site and take the data of each page etc aswell as update and add to existing data. So finding a method of quickly navigating links and search bars with my inputted data would be very helpful.
Any suggestions would be greatly appreciated.
# a simple list that contains the names of each state
states = ["Alabama", "Alaska" ,"Arizona", "....."]
for state in states:
#code to look up the state in the searchbar of website
#figures being taken from website etc
break
Here is the rough idea i have
There are many options to accomplish this with Python. As #LD mentioned, you can use Selenium. Selenium is a good option if you need to interact with a websites UI via a headless browser. E.g clicking a button, entering text into a search bar, etc. If your needs aren't that complex, for instance if you just need to quickly scrape all the raw content from a web page and process it, than you should use the requests module from Python's standard library.
For processing raw content from a crawl, I would recommend beautiful soup.
Hope that helps!
I am trying to extract data from a web site and the data are in a table :
url=requests.get("xxxxx")
soup =BeautifulSoup(url.content)
table=soup.find_all("table")[0]
rows = table.find_all('tr')
I tried this code it works but only 42 lines are extracted and the source table contains 220 lines ?
someone tell me how to fix this.
Welcome.
2 possibilities. Javascript or website security.
requests is javscript agnostic and doesn't execute any javascript code. You'll want a headless browser solution (selenium is popular) that more closely mimicks a browser, especially when it comes to javascript.
Many websites don't want to be scraped and employ different methods to prevent it. The simplest form is checking the User-Agent value of the client (your Python script) or rate-throttling (20k refreshes a second isn't human). e.g., if the User-Agent is anything other than a known value, it'll behave differently (little or no data). Other forms of defense are more complex. Such as trying to play audio on your "browser" or polling your "browser"'s resolution. For that you'll need to investigate the site's behavior. This can take time. You can start off with either the Networking tab of your browser's developing tools (F12 on Firefox) or Zap Proxy for more refined control.
I want to get some information on a web page. I use requests.get to abstract the page. But I cannot find what I want. Checking it carefully, I found the info I want is in a list with a scrollbar. When I drag scrollbar down, more and more info is loaded. So I guess all the info in the list is not loaded yet when I get the page by module requests. I want to know what is happened in this process and How can I gather the information I want. (I am not familiar with Html language).
I want to know what is happened in this process
It sounds like when the user scrolls, the scrolling causes some javascript(js) to execute, and the js makes repeated requests to the server for more data. Unfortunately, the requests module cannot cause the javascript on an html page to execute--all you get back is the text of the js. The unable to execute javascript on an html page in order to retrieve what the user actually sees has been a problem for a long time. Fortunately, smart programmers have largely solved that problem. You need to use a different module. Check out the selenium module.
I am not familiar with Html language
Scraping web pages can get really tricky really fast, and some web pages proactively try to prevent computer programs from scraping their content, so you need to know both html and js in order to figure out what is going on.
I want to crawl a website having multiple pages and when a page number is clicked it is dynamically loaded.How to screen scrape it?
i.e as the url is not present as href or a how to crawl to other pages?
Would be greatful if someone helped me on this.
PS:URL remains the same when different page is clicked.
You should consider also Ghost.py, since it allows you tu run arbitrary javascript commands, fill forms and take snapshoot very quickly.
if you are using google chrome, you can check the url which is dynamically being called in
network->headers of the developer tools
so based on that you can identify whether it is a GET or POST request.
If it is a GET request you can find the parameters straight away from the url.
If it is a POST request you can find the parameters from form data in network->headers
of the developer tools.
You could look for the data you want in the javascript code instead of the HTML. This is usually a pain but you can do fun things with regular expressions.
Alternatively, some of the browser testing libraries like splinter work by loading the page up in an actual browser like firefox or chrome before scraping. One of those would work if you are running this on a machine with a browser installed.
Since this post has been tagged with python and web-crawler, Beautiful Soup has to be mentioned: http://www.crummy.com/software/BeautifulSoup/
Documentation here: http://www.crummy.com/software/BeautifulSoup/bs3/download/2.x/documentation.html
You can not do that easily since it is an ajax pagination (even with mechanize). Instead, open the source file of the page and try to know what is the url request used for the ajax pagination. Then, you can create a fake request back and process the returned data by your own way
If you don't mind using gevent.GRobot is another good choose.