Django，匹配查詢不存在

Question

我是Django的新手。當我在pycharm運行命令python manage.py runserver，我得到這樣

2017-12-03 05:09:56,952 - INFO - server - Listening on endpoint 
tcp:port=8000:interface=127.0.0.1 
Internal Server Error:/
Traceback (most recent call last): 
File "/Users/mac/anaconda/lib/python3.6/site-packages/django/core/handlers/exception.py", line 41, in innerresponse = get_response(request) 
File "/Users/mac/anaconda/lib/python3.6/site-packages/django/core/handlers/base.py", line 187, in _get_response response = self.process_exception_by_middleware(e, request) 
File "/Users/mac/anaconda/lib/python3.6/site-packages/channels/handler.py", line 243, in process_exception_by_middleware 
return super(AsgiHandler,self).process_exception_by_middleware(exception, request) 
File "/Users/mac/anaconda/lib/python3.6/site-packages/django/core/handlers/base.py", line 185, in _get_response response = wrapped_callback(request, *callback_args, **callback_kwargs) 
File "/Users/mac/PycharmProjects/590/flightmate/webapp/views.py", line 180, in index airlines = RecordSet.objects.get(name="airline") 
File "/Users/mac/anaconda/lib/python3.6/site-packages/django/db/models/manager.py", line 85, in manager_method 
return getattr(self.get_queryset(), name)(*args, **kwargs) 
File "/Users/mac/anaconda/lib/python3.6/site-packages/django/db/models/query.py", line 380, in get self.model._meta.object_name 
webapp.models.DoesNotExist: RecordSet matching query does not exist. 

錯誤消息的models.py的代碼是：

from __future__ import unicode_literals 
import uuid 
import datetime 
from django.db import models 

class RecordSet(models.Model): 
name = models.CharField(max_length=512) 
value = models.TextField() 
def __unicode__(self): 
    return "{0}: {1}".format(self.name, self.value) 

和models.py的父目錄的目錄webapp。任何建議表示讚賞，謝謝！

Answer 1

正如你可以回溯看到，這個問題是這樣的：

airlines = RecordSet.objects.get(name="airline") 

您檢索單個對象與get()並且由於它不存在，它返回DoesNotExist例外。這也是Django文檔在小節Retrieving a single object with get()

明確提到如果沒有結果匹配查詢，獲得（）將引發 DoesNotExist例外。此例外是正在執行查詢的 類的一個屬性 - 因此在上面的代碼中，如果 沒有主鍵爲1的Entry對象，則Django將引發 Entry.DoesNotExist。

要麼使用filter()或get()與try ... except聲明。如果您知道只有一個對象與您的查詢匹配，則應該使用get()，否則使用filter()。