问题

以下是代码的翻译部分：

这是视图：

class UserViewSet(viewsets.ViewSet):
  def list(self, request):
    queryset = User.objects.all()
    serializer = UserSerializer(queryset, many=True)
    return Response(serializer.data)
  
  def retrieve(self, request, pk=None):
    queryset = User.objects.all()
    user = get_object_or_404(queryset, pk=pk)
    serializer = UserSerializer(user)
    return Response(serializer.data)

URLs：

from django.urls import path
from .views import *
from rest_framework import routers

userl = UserViewSet.as_view({'get': 'list'})
userd = UserViewSet.as_view({'get': 'retrieve'})

router = routers.SimpleRouter()
router.register('users', UserViewSet, basename='user')

urlpatterns = [
  path('users/', userl, name='user-list'),
  path('users/<int:pk>/', userd, name='user-detail'),
  path('register', RegisterUserAPIView.as_view()),
  path('login/', LoginAPIView.as_view()),
  path('logout', LogoutAPIView.as_view()),
  path('products', ProductsViewSet.as_view({'get': 'list'})),
]

跟踪信息：

File "C:\Users\User\Desktop\erkin2\venv\lib\site-packages\routers\router.py", line 27, in db_for_read
    return settings.DATABASES.keys()[0]
TypeError: 'dict_keys' object is not subscriptable

我尝试使用`keys()`，但然后它说：

> 函数没有属性keys()。

class UserViewSet(viewsets.ViewSet):
  def list(self, request):
    queryset = User.objects.all()
    serializer = UserSerializer(queryset, many=True)
    return Response(serializer.data)
  
  def retrieve(self, request, pk=None):
    queryset = User.objects.all()
    user = get_object_or_404(queryset, pk=pk)
    serializer = UserSerializer(user)
    return Response(serializer.data)

from django.urls import path
from .views import *
from rest_framework import routers

userl = UserViewSet.as_view({'get': 'list'})
userd = UserViewSet.as_view({'get': 'retrieve'})

router = routers.SimpleRouter()
router.register(r'users', UserViewSet, basename='user')

urlpatterns = [
  path('users/', userl, name='user-list'),
  path('users/<int:pk>/', userd, name='user-detail'),
  path('register',RegisterUserAPIView.as_view()),
  path('login/', LoginAPIView.as_view()),
  path('logout', LogoutAPIView.as_view()),
  path('products', ProductsViewSet.as_view({'get': 'list'})),

]'login/', LoginAPIView.as_view()),
  path('logout', LogoutAPIView.as_view()),
  path('products', ProductsViewSet.as_view({'get': 'list'})),

]

  File "C:\Users\User\Desktop\erkin2\venv\lib\site-packages\routers\router.py", line 27, in db_for_read
    return settings.DATABASES.keys()[0]
TypeError: 'dict_keys' object is not subscriptable

答案1

得分: 1

明显并且也许逆直觉的是，字典的 `keys()` 方法并不返回一个键列表。让我们检查一下：
```python
d = {'a': 1, 'b': 2}

print(d.keys())
>>> dict_keys(['a', 'b'])

print(type(d.keys()))
>>> <class 'dict_keys'>

d.keys()[0]
>>> TypeError: 'dict_keys' 对象不可索引

这并不总是如此。在Python 2中，keys() 方法确实返回一个列表。参见这个旧问题。

要获取键的实际列表，您可以在字典上调用 list()：

print(list(d))
>>> ['a', 'b']

然后索引将按预期工作：

print(list(d)[0])
>>> a

因此，您可能希望将行 return settings.DATABASES.keys()[0] 更改为：

return list(settings.DATABASES)[0]

<details>
<summary>英文:</summary>

Apparently and perhaps counter-intuitively, the `keys()` method for dictionaries does not return a list of keys. Let&#39;s check:
```python
d = {&#39;a&#39;: 1, &#39;b&#39;: 2}

print(d.keys())
&gt;&gt;&gt; dict_keys([&#39;a&#39;, &#39;b&#39;])

print(type(d.keys()))
&gt;&gt;&gt; &lt;class &#39;dict_keys&#39;&gt;

d.keys()[0]
&gt;&gt;&gt; TypeError: &#39;dict_keys&#39; object is not subscriptable

This was not always so. In Python 2, the keys() method did return a list. See this old question.

To get an actual list of the keys, you can call list() on the dictionary:

print(list(d))
>>> ['a', 'b']

Then indexing works as expected:

print(list(d)[0])
>>> a

So you may want to change the line return settings.DATABASES.keys()[0] to this:

return list(settings.DATABASES)[0]