Django中'type'对象不可迭代

Question

我使用Django Rest Framework创建了一个简单的API，列出了学生和他们所在的大学。访问数据的URL是http://127.0.0.1:8000/api/v1/students/。在测试API时，我遇到了以下错误：

TypeError at /api/v1/students/
'type' object is not iterable

Internal Server Error: /api/v1/students/
Traceback (most recent call last):
  File "/Users/gilangramadhanilhami/Desktop/88sparses/shipment/tracking/lib/python3.6/site-packages/django/core/handlers/exception.py", line 35, in inner
    response = get_response(request)
  File "/Users/gilangramadhanilhami/Desktop/88sparses/shipment/tracking/lib/python3.6/site-packages/django/core/handlers/base.py", line 128, in _get_response
    response = self.process_exception_by_middleware(e, request)
  File "/Users/gilangramadhanilhami/Desktop/88sparses/shipment/tracking/lib/python3.6/site-packages/django/core/handlers/base.py", line 126, in _get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "/Users/gilangramadhanilhami/Desktop/88sparses/shipment/tracking/lib/python3.6/site-packages/django/views/decorators/csrf.py", line 54, in wrapped_view
    return view_func(*args, **kwargs)
  File "/Users/gilangramadhanilhami/Desktop/88sparses/shipment/tracking/lib/python3.6/site-packages/django/views/generic/base.py", line 69, in view
    return self.dispatch(request, *args, **kwargs)
  File "/Users/gilangramadhanilhami/Desktop/88sparses/shipment/tracking/lib/python3.6/site-packages/rest_framework/views.py", line 477, in dispatch
    request = self.initialize_request(request, *args, **kwargs)
  File "/Users/gilangramadhanilhami/Desktop/88sparses/shipment/tracking/lib/python3.6/site-packages/rest_framework/views.py", line 379, in initialize_request
    authenticators=self.get_authenticators(),
  File "/Users/gilangramadhanilhami/Desktop/88sparses/shipment/tracking/lib/python3.6/site-packages/rest_framework/views.py", line 273, in get_authenticators
    return [auth() for auth in self.authentication_classes]
TypeError: 'type' object is not iterable

我能在StackOverflow上找到一些解决方案，但并没有太多运气找到一个解决方案。我在views.py文件中使用APIView，想要了解为什么使用APIView（使用Viewset时也会出现这个问题）时会发生这种情况。

我尝试更改权限，但没有帮助。同时将many=True设置为“False”也无法解决这个问题。

有人有任何想法吗？提前致谢。

以下是其他文件，以更好地理解此问题。 models.py

from django.db import models

class University(models.Model):
    name = models.CharField(max_length=50)
    url = models.URLField(unique=True)

    class Meta:
        verbose_name = "University"
        verbose_name_plural = "Universities"

    def __str__(self):
        return self.name

class Student(models.Model):
    first_name = models.CharField(max_length=50)
    last_name = models.CharField(max_length=50)
    university = models.ForeignKey(University, on_delete=models.CASCADE,)

    class Meta:
        verbose_name = "Student"
        verbose_name_plural = "Students"


    def __str__(self):
        return '%s %s' % (self.first_name, self.last_name)

serializers.py

from rest_framework import serializers

from . import models

class StudentSerializer(serializers.ModelSerializer):
    class Meta:
        fields = (
            'id',
            'first_name',
            'last_name',
            'university'
        )
        model = models.Student

class UniversitySerializer(serializers.ModelSerializer):
    class Meta:
        fields = (
            'id',
            'name',
            'url'
        )
        model = models.University

views.py

from rest_framework.views import APIView
from rest_framework.response import Response

from . import models
from . import serializers

class ListStudent(APIView):
    def list(self, request, format=None):
        students = models.Student.objects.all()
        serializer = serializers.StudentSerializer(students, many=True)
        return Response(serializer.data)

students/urls.py

from django.urls import path

from . import views

urlpatterns = [
    path('', views.ListStudent.as_view(), name='student_list')
]

urls.py

from django.contrib import admin
from django.urls import path, include

urlpatterns = [
    path('admin/', admin.site.urls),
    path('api-auth/', include('rest_framework.urls', namespace='rest_framework')),
    path('api/v1/students/', include(('students.urls','students'), namespace='students')),
]

- Imperator123

---

追踪错误信息还有更多吗？您能将DEBUG设置为True吗？ - Daniel Roseman

@DanielRoseman 我已经在问题上编辑了一些额外的错误描述。此外，这是DEBUG=True。 - Imperator123

嗯，这似乎与您发布的代码无关。您能展示一下您的DEFAULT_AUTHENTICATION_CLASSES设置吗？ - Daniel Roseman

没关系，我已经解决了。DEFAULT_AUTHENTICATION_CLASSES 看起来像这样 `'DEFAULT_AUTHENTICATION_CLASSES': ( 'rest_framework.authentication.SessionAuthentication'),`。由于值应该是一个元组，所以我漏掉了一个逗号。无论如何，还是谢谢你 :) - Imperator123

Answer 1

我认为这只是一个小错误。我的'DEFAULT_AUTHENTICATION_CLASSES'如下所示：

REST_FRAMEWORK = {
    'DEFAULT_AUTHENTICATION_CLASSES': (
        'rest_framework.authentication.SessionAuthentication'

    ),
    'DEFAULT_PERMISSION_CLASSES': (
        'rest_framework.permissions.IsAuthenticatedOrReadOnly'
    ),
}

我在这里缺少一个简单的逗号,。它应该是这样的。

REST_FRAMEWORK = {
    'DEFAULT_AUTHENTICATION_CLASSES': (
        'rest_framework.authentication.SessionAuthentication',

    ),
    'DEFAULT_PERMISSION_CLASSES': (
        'rest_framework.permissions.IsAuthenticatedOrReadOnly',
    ),
}

我意识到了“可迭代”这个词的含义。希望这能帮助你。

- Imperator123

---

哦！！只是一个,，你节省了我的时间。谢谢。 - Akhil S