I have the class: 

```
class Training_unit(models.Model):
    name = models.CharField(max_length = 200)
    description = models.CharField(max_length = 200)

```

I want to return now the name and the description for that i tried these two methods:

```
def __str__(self):
    return force_bytes('%s %s' % (self.name, self.description))

```

and

```
def __str__(self):
    return '%s %s' % (self.name, self.description)

```

I found these function on 

> 
> [https://docs.djangoproject.com/en/1.8/ref/models/instances/#django.db.models.Model.**str**](https://docs.djangoproject.com/en/1.8/ref/models/instances/#django.db.models.Model.__str__)
> 
> 
> 

but on both it gaves me this error on my admin page:

![error message](https://i.stack.imgur.com/XEAW9.png)

**EDIT:**
Full Traceback message:

```
Environment:

Request Method: GET
Request URL: http://localhost:8000/admin/trainings/training_block/3/

Django Version: 1.8.2
Python Version: 3.4.2
Installed Applications:
('django.contrib.admin',
 'django.contrib.auth',
 'django.contrib.contenttypes',
 'django.contrib.sessions',
 'django.contrib.messages',
 'django.contrib.staticfiles',
 'trainings')
Installed Middleware:
('django.contrib.sessions.middleware.SessionMiddleware',
 'django.middleware.common.CommonMiddleware',
 'django.middleware.csrf.CsrfViewMiddleware',
 'django.contrib.auth.middleware.AuthenticationMiddleware',
 'django.contrib.auth.middleware.SessionAuthenticationMiddleware',
 'django.contrib.messages.middleware.MessageMiddleware',
 'django.middleware.clickjacking.XFrameOptionsMiddleware',
 'django.middleware.security.SecurityMiddleware')

Template error:
In template C:\Python34\lib\site-packages\django\contrib\admin\templates\admin\includes\fieldset.html, error at line 19
   __str__ returned non-string (type datetime.date)

   9 :             {% for field in line %}

   10 :                 <div{% if not line.fields|length_is:'1' %} class="field-box{% if field.field.name %} field-{{ field.field.name }}{% endif %}{% if not field.is_readonly and field.errors %} errors{% endif %}{% if field.field.is_hidden %} hidden{% endif %}"{% elif field.is_checkbox %} class="checkbox-row"{% endif %}>

   11 :                     {% if not line.fields|length_is:'1' and not field.is_readonly %}{{ field.errors }}{% endif %}

   12 :                     {% if field.is_checkbox %}

   13 :                         {{ field.field }}{{ field.label_tag }}

   14 :                     {% else %}

   15 :                         {{ field.label_tag }}

   16 :                         {% if field.is_readonly %}

   17 :                             <p>{{ field.contents }}</p>

   18 :                         {% else %}

   19 :                              {{ field.field }} 

   20 :                         {% endif %}

   21 :                     {% endif %}

   22 :                     {% if field.field.help_text %}

   23 :                         <p class="help">{{ field.field.help_text|safe }}</p>

   24 :                     {% endif %}

   25 :                 </div>

   26 :             {% endfor %}

   27 :         </div>

   28 :     {% endfor %}

   29 : </fieldset>

Traceback:
File "C:\Python34\lib\site-packages\django\core\handlers\base.py" in get_response
  164.                 response = response.render()
File "C:\Python34\lib\site-packages\django\template\response.py" in render
  158.             self.content = self.rendered_content
File "C:\Python34\lib\site-packages\django\template\response.py" in rendered_content
  135.         content = template.render(context, self._request)
File "C:\Python34\lib\site-packages\django\template\backends\django.py" in render
  74.         return self.template.render(context)
File "C:\Python34\lib\site-packages\django\template\base.py" in render
  209.                     return self._render(context)
File "C:\Python34\lib\site-packages\django\template\base.py" in _render
  201.         return self.nodelist.render(context)
File "C:\Python34\lib\site-packages\django\template\base.py" in render
  903.                 bit = self.render_node(node, context)
File "C:\Python34\lib\site-packages\django\template\debug.py" in render_node
  79.             return node.render(context)
File "C:\Python34\lib\site-packages\django\template\loader_tags.py" in render
  135.         return compiled_parent._render(context)
File "C:\Python34\lib\site-packages\django\template\base.py" in _render
  201.         return self.nodelist.render(context)
File "C:\Python34\lib\site-packages\django\template\base.py" in render
  903.                 bit = self.render_node(node, context)
File "C:\Python34\lib\site-packages\django\template\debug.py" in render_node
  79.             return node.render(context)
File "C:\Python34\lib\site-packages\django\template\loader_tags.py" in render
  135.         return compiled_parent._render(context)
File "C:\Python34\lib\site-packages\django\template\base.py" in _render
  201.         return self.nodelist.render(context)
File "C:\Python34\lib\site-packages\django\template\base.py" in render
  903.                 bit = self.render_node(node, context)
File "C:\Python34\lib\site-packages\django\template\debug.py" in render_node
  79.             return node.render(context)
File "C:\Python34\lib\site-packages\django\template\loader_tags.py" in render
  65.                 result = block.nodelist.render(context)
File "C:\Python34\lib\site-packages\django\template\base.py" in render
  903.                 bit = self.render_node(node, context)
File "C:\Python34\lib\site-packages\django\template\debug.py" in render_node
  79.             return node.render(context)
File "C:\Python34\lib\site-packages\django\template\loader_tags.py" in render
  65.                 result = block.nodelist.render(context)
File "C:\Python34\lib\site-packages\django\template\base.py" in render
  903.                 bit = self.render_node(node, context)
File "C:\Python34\lib\site-packages\django\template\debug.py" in render_node
  79.             return node.render(context)
File "C:\Python34\lib\site-packages\django\template\defaulttags.py" in render
  217.                             nodelist.append(node.render(context))
File "C:\Python34\lib\site-packages\django\template\loader_tags.py" in render
  159.                 return template.render(context)
File "C:\Python34\lib\site-packages\django\template\base.py" in render
  211.                 return self._render(context)
File "C:\Python34\lib\site-packages\django\template\base.py" in _render
  201.         return self.nodelist.render(context)
File "C:\Python34\lib\site-packages\django\template\base.py" in render
  903.                 bit = self.render_node(node, context)
File "C:\Python34\lib\site-packages\django\template\debug.py" in render_node
  79.             return node.render(context)
File "C:\Python34\lib\site-packages\django\template\defaulttags.py" in render
  217.                             nodelist.append(node.render(context))
File "C:\Python34\lib\site-packages\django\template\defaulttags.py" in render
  217.                             nodelist.append(node.render(context))
File "C:\Python34\lib\site-packages\django\template\defaulttags.py" in render
  329.                 return nodelist.render(context)
File "C:\Python34\lib\site-packages\django\template\base.py" in render
  903.                 bit = self.render_node(node, context)
File "C:\Python34\lib\site-packages\django\template\debug.py" in render_node
  79.             return node.render(context)
File "C:\Python34\lib\site-packages\django\template\defaulttags.py" in render
  329.                 return nodelist.render(context)
File "C:\Python34\lib\site-packages\django\template\base.py" in render
  903.                 bit = self.render_node(node, context)
File "C:\Python34\lib\site-packages\django\template\debug.py" in render_node
  79.             return node.render(context)
File "C:\Python34\lib\site-packages\django\template\debug.py" in render
  92.             output = force_text(output)
File "C:\Python34\lib\site-packages\django\utils\encoding.py" in force_text
  90.                     s = six.text_type(s)
File "C:\Python34\lib\site-packages\django\utils\html.py" in <lambda>
  399.         klass.__str__ = lambda self: mark_safe(klass_str(self))
File "C:\Python34\lib\site-packages\django\forms\forms.py" in __str__
  543.         return self.as_widget()
File "C:\Python34\lib\site-packages\django\forms\forms.py" in as_widget
  599.         return force_text(widget.render(name, self.value(), attrs=attrs))
File "C:\Python34\lib\site-packages\django\contrib\admin\widgets.py" in render
  292.             'widget': self.widget.render(name, value, *args, **kwargs),
File "C:\Python34\lib\site-packages\django\forms\widgets.py" in render
  513.         options = self.render_options(choices, [value])
File "C:\Python34\lib\site-packages\django\forms\widgets.py" in render_options
  539.         for option_value, option_label in chain(self.choices, choices):
File "C:\Python34\lib\site-packages\django\forms\models.py" in __iter__
  1103.                 yield self.choice(obj)
File "C:\Python34\lib\site-packages\django\forms\models.py" in choice
  1110.         return (self.field.prepare_value(obj), self.field.label_from_instance(obj))
File "C:\Python34\lib\site-packages\django\forms\models.py" in label_from_instance
  1181.         return smart_text(obj)
File "C:\Python34\lib\site-packages\django\utils\encoding.py" in smart_text
  56.     return force_text(s, encoding, strings_only, errors)
File "C:\Python34\lib\site-packages\django\utils\encoding.py" in force_text
  90.                     s = six.text_type(s)

Exception Type: TypeError at /admin/trainings/training_block/3/
Exception Value: __str__ returned non-string (type datetime.date)

```