expressions.py 文件源码

def __init__(self, queryset, output_field=None, **extra):
        self.queryset = queryset
        self.extra = extra
        if output_field is None and len(self.queryset.query.select) == 1:
            output_field = self.queryset.query.select[0].field
        super(Subquery, self).__init__(output_field)