Django Model.ObjectDoesNotExist 异常

Question

在这里，我想获得匹配查询的获胜者。如果我没有那个赢家，我想去创造赢家

winner_check = Winner.objects.get(win_date__year=today.year, win_date__month=today.month, win_date__day=today.day)
if winner_check:
    final_winner = winner_check
    message = "Winner already generated for today."
    return anything

else:
    winner_index = random.randint(0, len(player_list)-1)
    winner = player_list[winner_index]
    return anything

这是正确的做法还是我应该产生异常

try:
    winner_check = Winner.objects.get(win_date__year=today.year, win_date__month=today.month, win_date__day=today.day)
    final_winner = winner_check
    message = "Winner already generated for today"
    return anything
except Winner.DoesNotExist:
    winner_index = random.randint(0, len(player_list)-1)
    final_winner = player_list[winner_index]
    return anything

如果我只想得到不创建怎么办

try:
    winner_check = Winner.objects.get(win_date__year=today.year, win_date__month=today.month, win_date__day=today.day)
except Winner.DoesNotExist:
    pass

如果没有用户，我想进一步处理返回一条消息，例如“没有赢家” 谁能指导我通过 get() 方法的异常

Answer 1

首先，我建议您将win_date 字段定义为models.DateField()，以便使用datetime.date 对象进行查找并避免在下面这样使用；

winner = Winner.objects.get(win_date__year=today.year, win_date__month=today.month, win_date__day=today.day)

相反，您将能够寻找这样的获胜者；

from django.utils import timezone

winner = Winner.objects.get(win_date=timezone.now().date())

至于您的问题，您可以使用get_or_create() 方法使用给定的win_date 搜索获胜者，如果找不到则创建一个新的。

winner, created = Winner.objects.get_or_create(win_date=timezone.now().date(), defaults={"name": "Vishnu", "surname": "Raj"})

if created:
    print "New winner has been generated"
else:
    print "Winner has already been generated for today"

---

对于您问题的第二部分，关于检索对象和处理DoesNotExist 异常，我建议您使用get_object_or_404()，它会在找不到对象时引发Http404 错误。

from django.utils import get_object_or_404
from django.http import Http404

def get_winner(request, id):
    try:
        winner = get_object_or_404(Winner, pk=id)
    except Http404:
        winner = Winner(win_date=..., name=..., surname=...)

在这种情况下，向用户发送404 错误而不是500 几乎总是更好的方法，因为 500 表示服务器错误，而 404 表示“未找到”。