Python 处理 Django 的 objects.get 的最佳方法是什么？
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What's the best way to handle Django's objects.get?
提问by TIMEX
Whenever I do this:
每当我这样做时：
thepost = Content.objects.get(name="test")
It always throws an error when nothing is found. How do I handle it?
当没有找到任何东西时，它总是会引发错误。我该如何处理？
采纳答案by Some programmer dude
try:
thepost = Content.objects.get(name="test")
except Content.DoesNotExist:
thepost = None
Use the model DoesNotExist exception
使用模型DoesNotExist 异常
回答by Rob Golding
Often, it is more useful to use the Django shortcut function get_object_or_404instead of the API directly:
通常，直接使用 Django 快捷功能get_object_or_404而不是 API更有用：
from django.shortcuts import get_object_or_404
thepost = get_object_or_404(Content, name='test')
Fairly obviously, this will throw a 404 error if the object cannot be found, and your code will continue if it is successful.
很明显，如果找不到对象，这将引发 404 错误，如果成功，您的代码将继续。
回答by Anurag Uniyal
Catch the exception
捕捉异常
try:
thepost = Content.objects.get(name="test")
except Content.DoesNotExist:
thepost = None
alternatively you can filter, which will return a empty list if nothing matches
或者，您可以过滤，如果没有匹配项，它将返回一个空列表
posts = Content.objects.filter(name="test")
if posts:
# do something with posts[0] and see if you want to raise error if post > 1
回答by zobbo
You can also catch a generic DoesNotExist. As per the docs at http://docs.djangoproject.com/en/dev/ref/models/querysets/
您还可以捕获通用的DoesNotExist。根据http://docs.djangoproject.com/en/dev/ref/models/querysets/ 上的文档
from django.core.exceptions import ObjectDoesNotExist
try:
e = Entry.objects.get(id=3)
b = Blog.objects.get(id=1)
except ObjectDoesNotExist:
print "Either the entry or blog doesn't exist."
回答by Banjer
Raising a Http404 exceptionworks great:
提高一个HTTP404异常的伟大工程：
from django.http import Http404
def detail(request, poll_id):
try:
p = Poll.objects.get(pk=poll_id)
except Poll.DoesNotExist:
raise Http404
return render_to_response('polls/detail.html', {'poll': p})
回答by Adil Malik
Handling exceptions at different points in your views could really be cumbersome..What about defining a custom Model Manager, in the models.py file, like
在视图中的不同点处理异常可能真的很麻烦..如何在 models.py 文件中定义自定义模型管理器，例如
class ContentManager(model.Manager):
def get_nicely(self, **kwargs):
try:
return self.get(kwargs)
except(KeyError, Content.DoesNotExist):
return None
and then including it in the content Model class
然后将其包含在内容模型类中
class Content(model.Model):
...
objects = ContentManager()
In this way it can be easily dealt in the views i.e.
这样就可以很容易地在视图中处理，即
post = Content.objects.get_nicely(pk = 1)
if post != None:
# Do something
else:
# This post doesn't exist
回答by Rafael Valverde
Another way of writing:
另一种写法：
try:
thepost = Content.objects.get(name="test")
except Content.DoesNotExist:
thepost = None
is simply:
很简单：
thepost = Content.objects.filter(name="test").first()
Note that the two are not strictly the same. Manager method getwill raise not only an exception in the case there's no recordyou're querying for but also when multiple recordsare found. Using firstwhen there are more than one record might fail your business logic silently by returning the first record.
请注意，两者并不严格相同。Manager 方法get不仅会在没有您要查询的记录的情况下引发异常，还会在找到多条记录时引发异常。使用first时，有一个以上的记录可能通过返回的第一条记录失败默默你的业务逻辑。
