How to set choices in dynamic with Django choicefield?

Question

I want to set choices in dynamic.

I used __set_choices method but, when request method is POST, is_valid method always return False.

if request.method=='POST':
 _form = MyForm(request.POST)
 if _form.is_valid():
   #something to do

Answer 1

I often set the choices dynamicly in the constructor:

class MyForm(BaseForm):
    afield = forms.ChoiceField(choices=INITIAL_CHOICES)

    def __init__(self, *args, **kwargs):
        super(MyForm, self).__init__(*args, **kwargs)
        self.fields['afield'].choices = my_computed_choices