[Fixed]-Show loading gif during long processing in django?

You can use Block UI for this purpose, it’s a JavaScript library.

Replace <input type="submit" class="btn btn-default" value="Save" > with

<button type="button" class="btn btn-default" onclick="submit_form()">Save</button>

Submit your form with JavaScript and upon submitting form, show image you want to show. You can watch demos here.