Django管理员导入导入导出-'NoneType'对象不可调用

Question

在Django管理页面中，我试图使用import_export库导入学生表，但它提供了

  在/ admin / catalog / student / import /的

TypeError不是'NoneType'对象   可调用的请求方法：POST请求URL：
  http://127.0.0.1:8000/admin/catalog/student/import/ Django版本：   2.2.2异常类型：TypeError异常值：'NoneType'对象不可调用异常位置：   C：\ Users \ sdixit23.EAD \ Envs \ my_django_environment \ lib \ site-packages \ import_export \ admin.py   在write_to_tmp_storage中，第229行Python可执行文件：   C：\ Users \ sdixit23.EAD \ Envs \ my_django_environment \ Scripts \ python.exe   Python版本：3.7.3 Python路径：
  ['C：\ Users \ sdixit23.EAD \ django_projects \ django_projects \ glacier'，   'C：\ Users \ sdixit23.EAD \ Envs \ my_django_environment \ Scripts \ python37.zip'，   'C：\ Users \ sdixit23.EAD \ Envs \ my_django_environment \ DLLs'，   'C：\ Users \ sdixit23.EAD \ Envs \ my_django_environment \ lib'，   'C：\ Users \ sdixit23.EAD \ Envs \ my_django_environment \ Scripts'，   'c：\ users \ sdixit23.ead \ appdata \ local \ programs \ python \ python37-32 \ Lib'，   'c：\ users \ sdixit23.ead \ appdata \ local \ programs \ python \ python37-32 \ DLLs'，   'C：\ Users \ sdixit23.EAD \ Envs \ my_django_environment'，   'C：\ Users \ sdixit23.EAD \ Envs \ my_django_environment \ lib \ site-packages'，   'C：\ Users \ sdixit23.EAD \ Envs \ my_django_environment \ lib \ site-packages \ odf'，   'C：\ Users \ sdixit23.EAD \ Envs \ my_django_environment \ lib \ site-packages \ odf'，   'C：\ Users \ sdixit23.EAD \ Envs \ my_django_environment \ lib \ site-packages \ odf'，   'C：\ Users \ sdixit23.EAD \ Envs \ my_django_environment \ lib \ site-packages \ odf'，   'C：\ Users \ sdixit23.EAD \ Envs \ my_django_environment \ lib \ site-packages \ odf'，   'C：\ Users \ sdixit23.EAD \ Envs \ my_django_environment \ lib \ site-packages \ odf'，   'C：\ Users \ sdixit23.EAD \ Envs \ my_django_environment \ lib \ site-packages \ odf']   服务器时间：2019年8月28日星期三17:31:27 +0100

我尝试检查models.py和admin.py文件。我什至尝试重新创建该站点，但是我不知道为什么它不起作用。 实际上，它不适用于我的任何模型。

admin.py

class StudentAdmin(ImportExportModelAdmin):
    list_display = ('student_ID',
                    'student_First_Name',
                    'student_Last_Name',
                    'student_DOB',
                    'gender',
                    'student_Gmail',
                    'parent_Name',
                    'parent_Email',
                    'contact_Number',
                    'city',
                    'country',
                    'comments',
                    )

# Register the admin class with the associated model
admin.site.register(Student, StudentAdmin)

models.py

class Student(models.Model):
    """Model representing a Student."""

    student_ID = models.CharField(primary_key=True, max_length=10, help_text='Enter Student ID as PYNNN')
    student_First_Name = models.CharField(max_length=100, help_text='Enter Student First Name')
    student_Last_Name = models.CharField(max_length=100, help_text='Enter Student First Name')
    student_DOB = models.DateField(help_text='Enter Date of Birth as YYYY-MM-DD', null=True)

    gender = models.CharField(
        max_length=10,
        choices=STUDENT_GENDER,
        blank=True,
        default='',
        help_text='Enter Student Gender',
    )

    student_Gmail = models.EmailField(max_length=100, help_text='Enter student Gmail-id. Its Mandatory to use Gmail-id', null=True)
    parent_Name = models.CharField(max_length=100, help_text='Enter Parent Full Name', null=True)
    parent_Email = models.EmailField(max_length=100, help_text='Enter Parent Email', null=True)
    contact_Number = models.CharField(max_length=11, help_text='Enter Mobile Number (e.g. 07910100045)', null=True)
    city = models.CharField(max_length=50, help_text='Enter City Name', null=True)
    country = CountryField(null=True, default= "United Kingdom")
    comments = models.TextField(max_length=200, help_text='Any Specific comments', null=True)

    def get_absolute_url(self):
        """Returns the url to access a particular student instance."""
        return reverse('student-detail', args=[str(self.pk)])

    def __str__(self):
        """String for representing the Model object."""
        return f'{self.student_First_Name} {self.student_Last_Name}'

预期结果是“预览页面”，相反，我看到此错误

TypeError at /admin/catalog/student/import/
'NoneType' object is not callable
Request Method: POST
Request URL:    http://127.0.0.1:8000/admin/catalog/student/import/
Django Version: 2.2.2
Exception Type: TypeError
Exception Value:    'NoneType' object is not callable
Exception Location: C:\Users\sdixit23.EAD\Envs\my_django_environment\lib\site-packages\import_export\admin.py in write_to_tmp_storage, line 229
Python Executable:  C:\Users\sdixit23.EAD\Envs\my_django_environment\Scripts\python.exe
Python Version: 3.7.3
Python Path:    ['C:\\Users\\sdixit23.EAD\\django_projects\\django_projects\\glacier',
 'C:\\Users\\sdixit23.EAD\\Envs\\my_django_environment\\Scripts\\python37.zip',
 'C:\\Users\\sdixit23.EAD\\Envs\\my_django_environment\\DLLs',
 'C:\\Users\\sdixit23.EAD\\Envs\\my_django_environment\\lib',
 'C:\\Users\\sdixit23.EAD\\Envs\\my_django_environment\\Scripts',
 'c:\\users\\sdixit23.ead\\appdata\\local\\programs\\python\\python37-32\\Lib',
 'c:\\users\\sdixit23.ead\\appdata\\local\\programs\\python\\python37-32\\DLLs',
 'C:\\Users\\sdixit23.EAD\\Envs\\my_django_environment',
 'C:\\Users\\sdixit23.EAD\\Envs\\my_django_environment\\lib\\site-packages',
 'C:\\Users\\sdixit23.EAD\\Envs\\my_django_environment\\lib\\site-packages\\odf',
 'C:\\Users\\sdixit23.EAD\\Envs\\my_django_environment\\lib\\site-packages\\odf',
 'C:\\Users\\sdixit23.EAD\\Envs\\my_django_environment\\lib\\site-packages\\odf',
 'C:\\Users\\sdixit23.EAD\\Envs\\my_django_environment\\lib\\site-packages\\odf',
 'C:\\Users\\sdixit23.EAD\\Envs\\my_django_environment\\lib\\site-packages\\odf',
 'C:\\Users\\sdixit23.EAD\\Envs\\my_django_environment\\lib\\site-packages\\odf',
 'C:\\Users\\sdixit23.EAD\\Envs\\my_django_environment\\lib\\site-packages\\odf']
Server time:    Wed, 28 Aug 2019 17:31:27 +0100