Changing a required field in a form based on a condition in views (Django)

Question

I have a LabelingForm () form with two multiple select fields, and I want to set the required parameter so that it is False when pressing buttons A and B, but True when pressing button C. I tried with initial = False and required = True, but it does not work, it requires a field to be selected when you press the A button.

in forms.py

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

in the template

<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>

Answer 1

Change the attribute required before calling is_valid():

   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():
          ...