查询 - 双下划线

    models.Book.objects.filter(id__gt=2)                    # 大于
    models.Book.objects.filter(id__lt=2)                    # 小于
    models.Book.objects.filter(id__in=[1,2,3])              # = 
    models.Book.objects.filter(title__contains="python")    # 包含
    models.Book.objects.filter(title__icontains="python")   # 不区分大小写


models.Publisher.objects.filter(book__title="python").values("name")

重要：从Publisher查book，双下划线

一对多，多对一都可以根据它的关联__xxx去查询