How to drag and drop a file with Selenium and Python (and JavaScript?)

I'm trying to build an app that uploads files to several sites (with the possibility of add more sites at any time). For this, I'm using Python with Selenium but I can't find a way to setup an drag and drop event/action. I just want to drag a local file and drop it on an HTML element (like a div or a form) to upload it. I've find a way to do it with this site but it just works with it because it triggers a specific JavaScript's function.

var jq = document.createElement('script');
jq.src = "https://ajax.googleapis.com/ajax/libs/jquery/1.11.2/jquery.min.js";
document.getElementsByTagName('head')[0].appendChild(jq);
// ... give time for script to load
jQuery.noConflict();

myOwnInput = window.jQuery('<input id="myOwnInput" type="file" />').appendTo('body');

function simulateDrop() {
    var fileInput = document.getElementById('myOwnInput'),
        file = fileInput.files[0];        
    holder.ondrop({ 
        dataTransfer: { files: [ file ] }, 
        preventDefault: function () {} 
    });
};

// Now I select a file with the input that I just added and then I execute the next line
simulateDrop();

That code it's not mine, I put together parts of code of (from here and here) because I don't know Javascript, but if it is necessary to do a drag and drop function for several sites, I can learn it with no problem. At the moment I think I can do it for each site studying how each one implement the drag and drop thing, but as I said, I will have to learn JavaScript and I don't know if there is a better way to achieve my goal. So I'm looking for a effective way to do the drag and drop action for several sites, preferably with Python but it is no exclusive.

For example, I tried to do it with uploadfiles.io but I can't make it work.

To summarize, what I need is advice on how to do the drag and drop action for files on different websites.