forms.py

class SolveExercise(forms.Form):
    CHOICES=[('opt_1',Exercise.opt_1),
                    ('opt_2',Exercise.opt_2),
                    ('opt_3',Exercise.opt_3),
                    ('opt_4',Exercise.opt_4)]
    choices = forms.ChoiceField(choices = CHOICES,widget = forms.RadioSelect() )

    class Meta:
        model = Exercise
        fields = ['choices']
    def __init__(self, *args, **kwargs):
        super(forms.Form, self).__init__(*args, **kwargs)

    def clean(self):
        cleaned_data = super(forms.Form, self).clean()
        return cleaned_data