From the View, how do I pass custom "choices" into a form's ChoiceField?

The get_initial method is made to populate the initial value of the fields of your form. Not to set the available choices or to modify your fields attributes.

To successfully passing your choices from your view to the form, you need to implement the get_form_kwargs method in your view:

class PairRequestView(FormView):
    form_class = PairRequestForm

    def get_form_kwargs(self):
        """Passing the `choices` from your view to the form __init__ method"""

        kwargs = super().get_form_kwargs()

        # Here you can pass additional kwargs arguments to the form.
        kwargs['favorite_choices'] = [('choice_value', 'choice_label')]

        return kwargs

And in your form, get the choices from the kwargs argument in the __init__ method and set the choices on the field:

class PairRequestForm(forms.Form):

    favorite_choices = forms.ChoiceField(choices=[], widget=RadioSelect, required=False)

    def __init__(self, *args, **kwargs):
        """Populating the choices of  the favorite_choices field using the favorites_choices kwargs"""

        favorites_choices = kwargs.pop('favorite_choices')

        super().__init__(*args, **kwargs)

        self.fields['favorite_choices'].choices = favorites_choices

And voilà !

Another simple way of doing this would be:

class PairRequestView(FormView):
    form_class = PairRequestForm

    def get_form(self, *args, **kwargs):
         requester_obj = Profile.objects.get(user__username=self.request.user)
         favorites_set = requester_obj.get_favorites()
         form = super().get_form(*args, **kwargs)
         form.fields['favorite_choices'].choices = favorites_set
         return form