编辑数据而不删除先前添加的数据。 Django使用'forms.Form'

Question

如何编辑数据而不删除以前添加的内容。在我的情况下，我想使用看起来像这样的form.Form

class SecondForm(forms.Form):
    data_1 = forms.ChoiceField(choices=CHOICES, label="")
    data_2 = forms.ChoiceField(choices=CHOICES, label="")
    data_3 = forms.ChoiceField(choices=CHOICES, label="")

在我的views.py

id = #some object number
if request.method =="POST":
    second_form = SecondForm(request.POST)
    if second_form.is_valid():
        cd = second_form.cleaned_data
        object = Valuation(pk=object_id)
        object.data_1 = cd['data_1']
        object.data_2 = cd['data_2']
        object.data_3 = cd['data_3']
        object.save()

        return HttpResponseRedirect(reverse('app:valuation_third', args=[forwarding]))
else:
    second_form = SecondForm()

在这种情况下，如果我的模型如下所示：

class Valuation(models.Model):
    data_added_before = models.CharField(max_length=50, blank=True)
    data_1 = models.CharField(max_length=50, blank=True)
    data_2 = models.CharField(max_length=50, blank=True)
    data_3 = models.CharField(max_length=50, blank=True)

每次清除字段“ data_added_before”时，都会对其进行清理。如何避免。因此，保留了该字段前面添加的信息。并将当前表单中的新数据添加到现有数据中。

编辑： 任何帮助将不胜感激。

Tempate.html

{% load crispy_forms_tags %}
          <form action="." method="post">
          <div class="">
            <h2 class="h3 text-primary font-weight-normal mb-4">More information></h2>
          </div>
            {% csrf_token %}
            <p>data_1 name</p>
            {{ second_form.data_1|as_crispy_field }}
            <p>data_2 name</p>
            {{ second_form.data_2|as_crispy_field }}
            <p>data_3 name</p>
            {{ second_form.data_3|as_crispy_field }}
            <div class="form-row">
              <div class="form-group col-md-6 mb-0">
                <form>
                  <input class="btn btn-text btn-text-secondary" type="button" value="before" onclick="history.back()">
                </form>
              </div>
              <div class="form-group col-md-6 mb-0">
                <div class="text-right">
                    <button type="submit" class="btn btn-primary">next <i class="fas fa-angle-right fa-lg"></i></button>
                </div>
              </div>
            </div>

          </form>