I solved the question in the follow way:

I created a hidden input to receive the list by javascript:

    <script>
        function addlist() {
            var array = []
            var checkboxes = document.querySelectorAll('input[type=checkbox]:checked')

            for (var i = 0; i < checkboxes.length; i++) {
                array.push(checkboxes[i].value);
            }

            document.getElementById('precedent_list').value = array;
        }
    </script>


<input  type="hidden" style="outline-style: none;" id="precedent_list" name="precedent_list">

And I call the javascript function when the submit button is clicked:

    <p class="w3-center" style="padding-top: 25px; padding-bottom: 25px">
          <button class="w3-round-xxlarge general_button" type="submit" onclick="addlist()">Salvar</button>
   </p>

In views.py I receive the list in the follow way:

my_list = ''
my_list_= []
if 'precedent_list' in request.POST:
    my_list = request.POST['precedent_list']
my_list = my_list.replace(',',' ')
for j in my_list.split():
    my_list_.append(int(j))