Python 根据视图中的条件更改表单中的必填字段（Django）

我有一个表单，LabelingForm（），有两个多个EchoiceFields，我希望设置required-参数，以便在按下按钮a和B时为False，但在按下按钮C时为True。我尝试过使用initial=False和required=True，但不起作用，按下按钮a时需要字段选择

在forms.py中

class LabelingForm(forms.Form):



    First_choices = (('1',''),

             .....
            )

    First_choice = forms.MultipleChoiceField(choices=First_choices, initial=True,required=True)


    Second__choices = (('1',''),

      .....
            )

   Second_choice = forms.MultipleChoiceField(choices=Second_choices, initial=True,required=True)

in views.py

def function(request, postID):
       if request.method == 'POST':
          form = LabelingForm(request.POST)
          if form.is_valid():

        if "A" in request.POST:
             # required is false 

        if "B" in request.POST:
             # required is false 

        if "C" in request.POST:
             # required is true
           # change required to True 
            form.fields['First_choice'].required = True
            form.fields['Second_choice'].required = True

模板中

<form  action="" method="post">{% csrf_token %}
 <input type="submit"  name="A" value="Submit A"></input>

 <input type="submit"  name="B" value="Submit B"></input>
 # change so that required is True
 {{ labelingform.first_choice}}{{ labelingform.second_choice}}<input type="submit"  name="C" value="Submit C"></input>

</form>

{%csrf\u令牌%}
#更改以使所需为真
{{labelingform.first_choice}{{labelingform.second_choice}

在调用

有效（）之前更改
required
属性：

只需提到，在较新版本中，它应该是：form.fields['First_choice'].required=True form.fields['Second_choice'].required=True
   if request.method == 'POST':
      form = LabelingForm(request.POST)

      required = 'C' in request.POST
      form.fields['First_choice'].required = required
      form.fields['Second_choice'].required = required

      if form.is_valid():
          ...