Obtaining Required Keys For Application/x-www-form-urlencoded

I have been using mechanize to fill in a form from a website but this now has changed and some of the required fields seem to be hidden and cannot be accessed using mechanize any l

Solution 1:

You cannot, in all circumstances, extract all fields a server expects.

The post target, the code handling the POST, is a black box. You cannot look inside the code that the server runs. The best information you have about what it expects is what the original form tells your browser to post. That original form consists not only of the HTML, but also of the headers that were sent with it (cookies for example) and any JavaScript code that is run by the browser.

In many cases, parsing the HTML sent for the form is enough; that's what Mechanize (or a recent more modern framework like robobrowser) does, plus a little cookie handling and making sure typical headers such as the referrer are included. But if any JavaScript code manipulated the HTML or intercepts the form submission to add or remove data then Mechanize or other Python form parsers cannot replicate that step.

Your options then are to:

• Reverse engineer what the Javascript code does and replicate that in Python code. The development tools of your browser can help here; observe what is being posted on the network tab, for example, or use the debugger to step through the JavaScript code to see what it does.

• Use an actual browser, controlled from Python. Selenium could do this for you; it can drive a desktop browser (Chrome, Firefox, etc.) or it can be used to drive a headless browser implementation such as PhantomJS. This is heavier on the resources, but will actually run the JavaScript code and let you post a form just as your browser would, in each and every way.