TypeError：类型为class的对象没有len（）

Question

当我尝试通过管理面板将数据添加到Faculty模型时，上传照片给我错误：

在/ admin / institute / faculty / add /中的TypeError
“部门”类型的对象没有len（）

models.py：

    MEDIA_ROOT_IMAGES = 'images/'

    def __get_path_faculty__(instance, filename):
        upload_dir = os.path.join(MEDIA_ROOT_IMAGES,instance.dept,'Faculty')
        if not os.path.exists(upload_dir):
            os.makedirs(upload_dir)
        return os.path.join(upload_dir, filename)

    class Department(models.Model):
        dept_code = models.CharField(unique=True, max_length = 2, primary_key = True, blank = False)
        .....

    class Faculty(models.Model):
        name = models.CharField(max_length = 50, blank = False)
        dept = models.ForeignKey(Department, blank=False)
        photo = models.ImageField(upload_to = __get_path_faculty__, default = 'null')
        .....
        faculty_id = models.CharField(unique=True, max_length =100, editable = False)
        def save(self, *args, **kwargs):
            if not self.faculty_id:
                self.faculty_id = self.email_off.split('@')[0]
            super(Faculty,self).save(*args,**kwargs)

views.py：

    def faculty(request,dept_code):
        dept_code1 = dept_code[:2].upper()
        try:
            dept = Department.objects.get(dept_code = dept_code1)
            context_dict['Department'] = dept
        except:
            raise Http404
        try:
            faculties = Faculty.objects.filter(dept=dept_code1)
            context_dict['Faculties'] = faculties

        except:
            raise Http404
        return render(request,'faculty.html',context_dict)

追溯：

File "C:\Users\shiva\Anaconda\lib\site-packages\django\core\handlers\base.py" in get_response
  132.                     response = wrapped_callback(request, *callback_args, **callback_kwargs)
File "C:\Users\shiva\Anaconda\lib\site-packages\django\contrib\admin\options.py" in wrapper
  616.                 return self.admin_site.admin_view(view)(*args, **kwargs)
File "C:\Users\shiva\Anaconda\lib\site-packages\django\utils\decorators.py" in _wrapped_view
  110.                     response = view_func(request, *args, **kwargs)
File "C:\Users\shiva\Anaconda\lib\site-packages\django\views\decorators\cache.py" in _wrapped_view_func
  57.         response = view_func(request, *args, **kwargs)
File "C:\Users\shiva\Anaconda\lib\site-packages\django\contrib\admin\sites.py" in inner
  233.             return view(request, *args, **kwargs)
File "C:\Users\shiva\Anaconda\lib\site-packages\django\contrib\admin\options.py" in add_view
  1516.         return self.changeform_view(request, None, form_url, extra_context)
File "C:\Users\shiva\Anaconda\lib\site-packages\django\utils\decorators.py" in _wrapper
  34.             return bound_func(*args, **kwargs)
File "C:\Users\shiva\Anaconda\lib\site-packages\django\utils\decorators.py" in _wrapped_view
  110.                     response = view_func(request, *args, **kwargs)
File "C:\Users\shiva\Anaconda\lib\site-packages\django\utils\decorators.py" in bound_func
  30.                 return func.__get__(self, type(self))(*args2, **kwargs2)
File "C:\Users\shiva\Anaconda\lib\site-packages\django\utils\decorators.py" in inner
  145.                     return func(*args, **kwargs)
File "C:\Users\shiva\Anaconda\lib\site-packages\django\contrib\admin\options.py" in changeform_view
  1467.                 self.save_model(request, new_object, form, not add)
File "C:\Users\shiva\Anaconda\lib\site-packages\django\contrib\admin\options.py" in save_model
  1078.         obj.save()
File "C:\Users\shiva\Documents\GitHub\iitbhu - Copy (3)\src\institute\models.py" in save
  130.         super(Faculty,self).save(*args,**kwargs)
File "C:\Users\shiva\Anaconda\lib\site-packages\django\db\models\base.py" in save
  710.                        force_update=force_update, update_fields=update_fields)
File "C:\Users\shiva\Anaconda\lib\site-packages\django\db\models\base.py" in save_base
  738.             updated = self._save_table(raw, cls, force_insert, force_update, using, update_fields)
File "C:\Users\shiva\Anaconda\lib\site-packages\django\db\models\base.py" in _save_table
  822.             result = self._do_insert(cls._base_manager, using, fields, update_pk, raw)
File "C:\Users\shiva\Anaconda\lib\site-packages\django\db\models\base.py" in _do_insert
  861.                                using=using, raw=raw)
File "C:\Users\shiva\Anaconda\lib\site-packages\django\db\models\manager.py" in manager_method
  127.                 return getattr(self.get_queryset(), name)(*args, **kwargs)
File "C:\Users\shiva\Anaconda\lib\site-packages\django\db\models\query.py" in _insert
  920.         return query.get_compiler(using=using).execute_sql(return_id)
File "C:\Users\shiva\Anaconda\lib\site-packages\django\db\models\sql\compiler.py" in execute_sql
  970.             for sql, params in self.as_sql():
File "C:\Users\shiva\Anaconda\lib\site-packages\django\db\models\sql\compiler.py" in as_sql
  928.                 for obj in self.query.objs
File "C:\Users\shiva\Anaconda\lib\site-packages\django\db\models\fields\files.py" in pre_save
  315.             file.save(file.name, file, save=False)
File "C:\Users\shiva\Anaconda\lib\site-packages\django\db\models\fields\files.py" in save
  90.         name = self.field.generate_filename(self.instance, name)
File "C:\Users\shiva\Documents\GitHub\iitbhu - Copy (3)\src\institute\models.py" in __get_path_faculty__
  17.     upload_dir = os.path.join(MEDIA_ROOT_IMAGES,instance.dept,'Faculty')
File "C:\Users\shiva\Anaconda\lib\ntpath.py" in join
  66.         p_drive, p_path = splitdrive(p)
File "C:\Users\shiva\Anaconda\lib\ntpath.py" in splitdrive
  114.     if len(p) > 1:

Exception Type: TypeError at /admin/institute/faculty/add/
Exception Value: object of type 'Department' has no len()

Answer 1

这是导致错误的行：

upload_dir = os.path.join(MEDIA_ROOT_IMAGES,instance.dept,'Faculty')

instance.dept是Department一个实例。 您可能想要的是部门代码。 这可以通过instance.dept.dept_code进行访问。

Answer 2

您正在收到此错误，因为在Department类中没有定义len()函数。 而且，似乎您正在尝试对Department类的实例执行.len() 。

Answer 3

为了在类上使用len（）方法，您需要在类中实现len方法。 此处的更多信息： http : //www.diveintopython.net/object_directional_framework/special_class_methods2.html