python - Django model.objects.all() 在正常调用时给出超出范围的列表索引

Question

所以我目前正在使用 Django 开发一个私有(private)项目，当我尝试为团队加载页面时，它只是说“列表索引超出范围”，我正在使用 object.all() 从模型团队中获取每个团队，

在模板中，我使用 for 循环将每个团队发布到页面上，我一直在尝试使用 order_by() 和 first()，但它们似乎都没有帮助。

我的回溯在这里http://dpaste.com/2S4Q7FY

我在这里做错了什么我应该改变什么

观点

def teams(request):
    teams = Team.objects.all()
    context = {
        'teams': teams,
    }
    if request.user.is_authenticated():
        logged_in_user = get_object_or_404(User, pk=request.user.pk)
        context['logged_in_user'] = logged_in_user
    return render(request, 'teams.html', context)

模范队

class Team(models.Model):
    name = models.CharField(max_length=16)
    logo = models.ImageField(upload_to='teams/avatars', default='static/img/userpreload.png')
    background = models.ImageField(upload_to='teams/backgrounds', default='static/img/userpreload.png')
    description = models.TextField(blank=True)
    people_needed = models.PositiveSmallIntegerField()
    members = models.ManyToManyField(User, through='TeamMembership')
    accepts_applications = models.BooleanField()

    @property
    def teamleaders_listable(self):
        leaders = self.members.filter(teammembership__leader=True)
        string = leaders[0].extendeduser.nickname

        for leader in leaders[1:]:
            string += ", " + leader.extendeduser.nickname

        return string

    @property
    def multiple_teamleaders(self):
        if len(self.members.filter(teammembership__leader=True)) > 1:
            return True
        else:
            return False


    def __str__(self):
        return self.name

Answer 1

回溯的关键部分是:

File "/home/melonendk/webapps/victory_genki_dk/victory/staff/models.py" in teamleaders_listable
  22.       string = leaders[0].extendeduser.nickname

File "/home/melonendk/webapps/victory_genki_dk/lib/python3.6/Django-1.11.6-py3.6.egg/django/db/models/query.py" in __getitem__
  289.         return list(qs)[0]

Exception Type: IndexError at /teams/
Exception Value: list index out of range

这告诉您 leaders[0] 失败了，因为 self.members.filter(teammembership__leader=True) 是一个空查询集。

您可以稍微更改代码以使用 ", ".join() 而不是遍历查询集。当查询集为空时，这将返回空字符串 ''。

@property
def teamleaders_listable(self):
    leaders = self.members.filter(teammembership__leader=True)
    return ", ".join(l.extendeduser.nickname for l in leaders)