forms.py 文件源码

def __iter__(self):
        if self.field.group_by is None:
            yield from super().__iter__()
            return

        if self.field.empty_label is not None:
            yield ("", self.field.empty_label)

        qs = self.queryset
        if self.field.is_relation:
            if self.field.group_by not in qs.query.order_by:
                qs.query.order_by.insert(0, self.field.group_by)
            qs = qs.select_related(self.field.group_by)

        groups = groupby(
            qs.all(),
            key=lambda row: getattr(row, self.field.group_by)
        )
        for group, choices in groups:
            yield smart_text(group), [self.choice(ch) for ch in choices]