python - 当我尝试删除对象时出现 "list out of index range"错误

Question

这是我的 delete_category 函数:

def delete_category(request, id):
    user = request.user
    category = Category.objects.get(pk=id)
    category.user.remove(user)
    return HttpResponseRedirect(reverse('auth_profile', args=[user.username]))

这是我的 category_detail 函数:

def category_detail(request, category_name):
    user = request.user
    category = Category.objects.filter(name=category_name, user__username=user)[0]
    return render_to_response("category_detail.html", { "category":category}, context_instance=RequestContext(request))

这是 category_detail.html:

        <p>{{category.name}}</p>
        <a href="{% url 'delete_category' category.id %}">delete</a>

如果我有多个类别，我可以在点击删除链接时删除。但是，如果我只有一个类别，则会出现此错误:

列表索引超出范围

Answer 1

改变

category = Category.objects.filter(name=category_name, user__username=user)[0]

通过

categories = Category.objects.filter(name=category_name, user__username=user)
category = None
if categories:
   category = categories[0]

另请参阅如何正确使用 QuerySet 对象 here