how to refresh django control without model

I'd like to refresh django control(without model) after updating. (created the userForm by forms.py) Is this method feasible? if possible, tell me how to write code.

forms.py

class test_Form(forms.Form):

    # userID
    user_id = forms.ChoiceField(
        label = "userID",
        widget= forms.Select(),
    )

    def __init__(self,  *args, **kwargs):
        super().__init__(*args, **kwargs)

        # userID-source
        sql_user_id = """
            select distinct
                user_id ,
                user_id as disp_user_id 
            from hoge
            order by user_id
        """
        df_user_id = db.dataframe(sql_user_regrole) // <- result in dataframe
        self.fields["user_id"].choices = tuple(df_user_id .itertuples(index=False , name = None))

views.py

def view(request):
    return render(request, "test.html",  {'form': test_Form()})

def Regist(request):
    // update process...

    return ??(what should I return to client)

push btn_exe , input text regist to DB-table. and refresh userid(select box). test.html

<script>
    $(document).on("click","#btn_exe",function(){
        RegistExecute();
    });

    function RegistExecute() {
        var formData = $('#userForm').serialize();
        var postData = {
            type : "POST",
            dataType : "text",
            data : formData,
            processData : false,
            contentType : false
        };
        //exe   
        $.ajax(URL, postData)
            .done(function(){
                alert("data update finished.");
                //  how to refresh control??
            });
</script>
<html>
<body class="">
    {% load static%}

    {{ form.media }}

    <form class="form-inline" id="userForm">
            {{ form.user_id}}
            <input type="text" id= "add_user"/>
        {% csrf_token %}
        <button type="button" id="btn_exe" class="">ADD USER</button>
    </form>

please help me~~~~!!!(>_<)