request.method == 'post' django code example

Example: request.post django

Read about request objects that your views receive: https://docs.djangoproject.com/en/dev/ref/request-response/#httprequest-objects

Also your hidden field needs a reliable name and then a value:

<input type="hidden" name="title" value="{{ source.title }}">
Then in a view:

request.POST.get("title", "")