djangoでchoicefield（セレクトボックス）を含むformのformsetを使う場合の選択肢の注入のパターン(form)

django-formset-choicefield-forms.py

class ArticleSelectForm(forms.Form):
    title = forms.CharField(
        widget=forms.TextInput(attrs={'placeholder': _(u'内容'), 'size': 60, }),
    )
    article_group = forms.ChoiceField(
        widget=forms.Select(),
        choices=[],
        required=False,
    )


ArticleSelectFormSet = formsets.formset_factory(ArticleSelectForm, extra=1, max_num=100)