Star 4. Mechanize is a ruby library that makes automated web interaction easy. MIT License. Branches Tags. Could not load branches. Could not load tags. Latest commit. Each link goes to a page that lists the given committee's filings. The links are in this format:. This particular link goes to the filings from the principal campaign committee with U. Senator Daniel Inouye D-Hawaii. Now things get a little more interesting. Here's what a committee's filings page looks like:.
All the links for the PDF filings are conveniently in the last column of the tables. In the next-to-last column are links to page-by-page browse the PDFs, which we can ignore for now as we want the whole files for download.
For reports that were filed electronically in more recent years, the links go directly to actual PDF files, which are pretty straightforward to download. The URLs look like:. If you follow this sample link, it does not go to a PDF. Instead, you're directed to an intermediary page that prompts you to click a button — helpfully labeled "Generate PDF" — before dynamically generating the desired PDF:.
Which then sends us to a PDF to view in-browser. It doesn't have any unique identifier that would correspond to a file and so is likely not a direct link to the PDF. So the page created by the PDF-generation operation isn't a deep-link. But if by inspecting the source , we see that the server has sent over a webpage that basically consists of an embedded PDF:.
So how does our scraper "push" the button to get the server to build out those PDFs? We look for the POST request triggered by the button. So go back to the individual report page that has the "Generate PDF" button. Activate your network panel. And click the button.
The POST request may disappear before you get a chance to examine it, but it will look like this:. That button is actually part of an HTML form — which we will inspect in the next step.
I've highlighted the two parameters: the keys are in orange and their values are in blue. Go back to the page with the "Generate PDF" button again and now inspect the source.
I've found that with particularly large PDFs, this script will fail. I think it's a matter of choosing a lower-level Ruby HTTP library and configuring settings so that it keeps a persistent connection while awaiting the server's response. I may revisit this issue in a later update to this chapter. The purpose of this chapter is to give you real-world examples of how to put together a scraper that can navigate a multi-level website.
So this next section is just a combination of all the concepts and code we've covered so far. I've broken the code down into four pieces: the first three are custom methods that handle downloading and parsing the pages. Note: I use a Ruby construct called a Module to namespace the method names. This is something I cover in brief in the object-oriented programming chapter. But there's nothing to it beyond just organizing the methods inside a wrapper. Refer back to previous sections on inspecting the search page's POST request.
Refer back to the previous sections on the filings list page and how to "push a button". The previous 3 code snippets were self-contained methods. This step involves writing a loop that calls these methods in appropriate order and passing the appropriate parameters to each successive step. The actual file-saving-to-disk happens here, too. Calls each of the three previous methods. The first two return collections of links that need to be iterated through. The third method, FECImages.
There are some design concepts here that we haven't previously covered, most notably the use of modules to namespace methods covered in more detail in the object-oriented concepts chapter. There's no reason that I couldn't have defined my methods without them.
The table below compares the two styles:. I chose to separate all the code into two files: one for the main loop and one " fecimg-module. The file with the main loop has to require the other file. What's the point of all this extra setup?
Solely for the sake of keeping things clean. For complex projects, keeping everything in a giant code file can slow you down because you're constantly scanning for where you put what code. Keeping separate files and using require cuts down on that constant searching. It also helps to emphasize a design pattern of encapsulation , in which methods are self-contained black boxes that do not need to be aware of each others' implementation details.
Each method need only worry about its own preconditions and expected return values. Likewise, the main loop doesn't need to be aware of how each method does its job. It just needs to know what each method takes in and returns. In fact, in the. Only the methods inside the FECImages module need those, so the require statements can be put there. This example isn't a perfect example of encapsulation.
But this is a relatively small project so I let myself be a little sloppy. It uses Nokogiri for parsing and makes all the form manipulation pretty easy. I like it because it does away most of the annoying web inspecting work and handles some of the more complicated browser-like behavior, such as cookies and authentication. There are some sites that I have not been able to scrape without using Mechanize.
Sign up using Email and Password. Post as a guest Name. Email Required, but never shown. The Overflow Blog. Podcast Making Agile work for data science. Stack Gives Back Featured on Meta. New post summary designs on greatest hits now, everywhere else eventually. Linked Just find the file upload field, and tell it what file name you want to upload:. Mechanize uses nokogiri to parse HTML. What does this mean for you? You can treat a mechanize page like an nokogiri object.
After you have used Mechanize to navigate to the page that you need to scrape, then scrape it using nokogiri methods:. Skip to content. Star 4. Permalink main. Branches Tags. Could not load branches. Could not load tags. Raw Blame. Open with Desktop View raw View blame.
Let's Fetch a Page! Next, let's try finding some links to click. Now that we've fetched google's homepage, let's try listing all of the links: page.
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