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[解決済み] Unicodeに強制変換する:文字列またはバッファが必要、django adminでレンダリングするとNoneTypeが検出される。

2022-02-13 15:59:39

質問

私は長い間このエラーを持っていますが、それを理解することはできません。

Caught TypeError while rendering: coercing to Unicode: need string or buffer, NoneType found.

管理画面でモデルの一つを追加または変更しようとすると発生します(表示は正常に動作します)。

これがそのモデルです。

class PS(models.Model):
    id_ps = models.IntegerField(null=True)
    client = models.ForeignKey(Client, null=True, blank=True)
    nom_du_site = models.CharField(max_length=250)
    rue_livraison = models.TextField(null=True)
    complement_adresse = models.TextField(null=True)
    code_postal_livraison = models.CharField(max_length=50, null=True)
    ville_livraison = models.CharField(max_length=200, null=True)
    pays_livraison = models.CharField(max_length=200, null=True)
    distributeur = models.CharField(max_length=50, null=True)
    tarif = models.CharField(max_length=250, null=True)
    type_tarif = models.CharField(max_length=50, null=True)
    type_installation = models.CharField(max_length=50, null=True)

    def __unicode__(self):
        return self.nom_du_site

    @property
    def pce(self):        
        try:
            return PCE.objects.filter(ps=self)[0]
        except IndexError:
            return
    #    
    def get_pce(self):
        from pce.models import PCE
        return PCE.objects.filter(ps=self).exclude(frequence='6M')
    #
    def get_pce_6m(self):
        from pce.models import PCE
        return PCE.objects.filter(ps=self,frequence='6M') 

何が間違っているのでしょうか?

トレースバック。

    Environment:

    Request Method: GET
    Request URL: http://127.0.0.1:8026/admin/ps/ps/add/
    Django Version: 1.2.5
    Python Version: 2.7.2
    Installed Applications:
    ['django.contrib.auth',
     'django.contrib.contenttypes',
     'django.contrib.sessions',
     'django.contrib.sites',
     'django.contrib.messages',
     'django.contrib.admin',
     'easy_thumbnails',
     'django_extensions',
     'contentadmin',
     'south',
     'sentry',
     'sentry.client',
     'indexer',
     'file_uploader',
     'paging',
     'pagination',
     'consommation',
     'ps',
     'pce',
     'profil',
     'analytics',
     'document']
    Installed Middleware:
    ('annoying.middlewares.StaticServe',
     'django.middleware.common.CommonMiddleware',
     'django.contrib.sessions.middleware.SessionMiddleware',
     'django.middleware.csrf.CsrfViewMiddleware',
     'django.contrib.auth.middleware.AuthenticationMiddleware',
     'django.contrib.messages.middleware.MessageMiddleware',
     'pagination.middleware.PaginationMiddleware')


    Template error:
    In template /usr/local/lib/python2.7/dist-packages/django/contrib/admin/templates/admin/includes/fieldset.html, error at line 19
       Caught TypeError while rendering: coercing to Unicode: need string or buffer, NoneType found
       9 :             {% for field in line %}


       10 :                 <div{% if not line.fields|length_is:'1' %} class="field-box{% if not field.is_readonly and field.errors %} errors{% endif %}"{% 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.field.help_text %}


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


       24 :                     {% endif %}


       25 :                 </div>


       26 :             {% endfor %}


       27 :         </div>


       28 :     {% endfor %}


       29 : </fieldset>


    Traceback:
    File "/usr/local/lib/python2.7/dist-packages/django/core/handlers/base.py" in get_response
      100.                     response = callback(request, *callback_args, **callback_kwargs)
    File "/usr/local/lib/python2.7/dist-packages/django/contrib/admin/options.py" in wrapper
      288.                 return self.admin_site.admin_view(view)(*args, **kwargs)
    File "/usr/local/lib/python2.7/dist-packages/django/utils/decorators.py" in _wrapped_view
      76.                     response = view_func(request, *args, **kwargs)
    File "/usr/local/lib/python2.7/dist-packages/django/views/decorators/cache.py" in _wrapped_view_func
      78.         response = view_func(request, *args, **kwargs)
    File "/usr/local/lib/python2.7/dist-packages/django/contrib/admin/sites.py" in inner
      190.             return view(request, *args, **kwargs)
    File "/usr/local/lib/python2.7/dist-packages/django/utils/decorators.py" in _wrapper
      21.             return decorator(bound_func)(*args, **kwargs)
    File "/usr/local/lib/python2.7/dist-packages/django/utils/decorators.py" in _wrapped_view
      76.                     response = view_func(request, *args, **kwargs)
    File "/usr/local/lib/python2.7/dist-packages/django/utils/decorators.py" in bound_func
      17.                 return func(self, *args2, **kwargs2)
    File "/usr/local/lib/python2.7/dist-packages/django/db/transaction.py" in _commit_on_success
      299.                     res = func(*args, **kw)
    File "/usr/local/lib/python2.7/dist-packages/django/contrib/admin/options.py" in add_view
      909.         return self.render_change_form(request, context, form_url=form_url, add=True)
    File "/usr/local/lib/python2.7/dist-packages/django/contrib/admin/options.py" in render_change_form
      692.         ], context, context_instance=context_instance)
    File "/usr/local/lib/python2.7/dist-packages/django/shortcuts/__init__.py" in render_to_response
      20.     return HttpResponse(loader.render_to_string(*args, **kwargs), **httpresponse_kwargs)
    File "/usr/local/lib/python2.7/dist-packages/django/template/loader.py" in render_to_string
      186.     return t.render(context_instance)
    File "/usr/local/lib/python2.7/dist-packages/django/template/__init__.py" in render
      173.             return self._render(context)
    File "/usr/local/lib/python2.7/dist-packages/django/template/__init__.py" in _render
      167.         return self.nodelist.render(context)
    File "/usr/local/lib/python2.7/dist-packages/django/template/__init__.py" in render
      796.                 bits.append(self.render_node(node, context))
    File "/usr/local/lib/python2.7/dist-packages/django/template/debug.py" in render_node
      72.             result = node.render(context)
    File "/usr/local/lib/python2.7/dist-packages/django/template/loader_tags.py" in render
      125.         return compiled_parent._render(context)
    File "/usr/local/lib/python2.7/dist-packages/django/template/__init__.py" in _render
      167.         return self.nodelist.render(context)
    File "/usr/local/lib/python2.7/dist-packages/django/template/__init__.py" in render
      796.                 bits.append(self.render_node(node, context))
    File "/usr/local/lib/python2.7/dist-packages/django/template/debug.py" in render_node
      72.             result = node.render(context)
    File "/usr/local/lib/python2.7/dist-packages/django/template/loader_tags.py" in render
      125.         return compiled_parent._render(context)
    File "/usr/local/lib/python2.7/dist-packages/django/template/__init__.py" in _render
      167.         return self.nodelist.render(context)
    File "/usr/local/lib/python2.7/dist-packages/django/template/__init__.py" in render
      796.                 bits.append(self.render_node(node, context))
    File "/usr/local/lib/python2.7/dist-packages/django/template/debug.py" in render_node
      72.             result = node.render(context)
    File "/usr/local/lib/python2.7/dist-packages/django/template/loader_tags.py" in render
      62.             result = block.nodelist.render(context)
    File "/usr/local/lib/python2.7/dist-packages/django/template/__init__.py" in render
      796.                 bits.append(self.render_node(node, context))
    File "/usr/local/lib/python2.7/dist-packages/django/template/debug.py" in render_node
      72.             result = node.render(context)
    File "/usr/local/lib/python2.7/dist-packages/django/template/defaulttags.py" in render
      174.                 nodelist.append(node.render(context))
    File "/usr/local/lib/python2.7/dist-packages/django/template/loader_tags.py" in render
      139.             return self.template.render(context)
    File "/usr/local/lib/python2.7/dist-packages/django/template/__init__.py" in render
      173.             return self._render(context)
    File "/usr/local/lib/python2.7/dist-packages/django/template/__init__.py" in _render
      167.         return self.nodelist.render(context)
    File "/usr/local/lib/python2.7/dist-packages/django/template/__init__.py" in render
      796.                 bits.append(self.render_node(node, context))
    File "/usr/local/lib/python2.7/dist-packages/django/template/debug.py" in render_node
      72.             result = node.render(context)
    File "/usr/local/lib/python2.7/dist-packages/django/template/defaulttags.py" in render
      174.                 nodelist.append(node.render(context))
    File "/usr/local/lib/python2.7/dist-packages/django/template/defaulttags.py" in render
      174.                 nodelist.append(node.render(context))
    File "/usr/local/lib/python2.7/dist-packages/django/template/defaulttags.py" in render
      260.             return self.nodelist_false.render(context)
    File "/usr/local/lib/python2.7/dist-packages/django/template/__init__.py" in render
      796.                 bits.append(self.render_node(node, context))
    File "/usr/local/lib/python2.7/dist-packages/django/template/debug.py" in render_node
      72.             result = node.render(context)
    File "/usr/local/lib/python2.7/dist-packages/django/template/defaulttags.py" in render
      260.             return self.nodelist_false.render(context)
    File "/usr/local/lib/python2.7/dist-packages/django/template/__init__.py" in render
      796.                 bits.append(self.render_node(node, context))
    File "/usr/local/lib/python2.7/dist-packages/django/template/debug.py" in render_node
      72.             result = node.render(context)
    File "/usr/local/lib/python2.7/dist-packages/django/template/debug.py" in render
      91.             output = force_unicode(output)
    File "/usr/local/lib/python2.7/dist-packages/django/utils/encoding.py" in force_unicode
      66.                 s = unicode(s)
    File "/usr/local/lib/python2.7/dist-packages/django/forms/forms.py" in __unicode__
      408.         return self.as_widget()
    File "/usr/local/lib/python2.7/dist-packages/django/forms/forms.py" in as_widget
      450.         return widget.render(name, data, attrs=attrs)
    File "/usr/local/lib/python2.7/dist-packages/django/contrib/admin/widgets.py" in render
      247.         output = [self.widget.render(name, value, *args, **kwargs)]
    File "/usr/local/lib/python2.7/dist-packages/django/forms/widgets.py" in render
      447.         options = self.render_options(choices, [value])
    File "/usr/local/lib/python2.7/dist-packages/django/forms/widgets.py" in render_options
      464.         for option_value, option_label in chain(self.choices, choices):
    File "/usr/local/lib/python2.7/dist-packages/django/forms/models.py" in __iter__
      898.                 yield self.choice(obj)
    File "/usr/local/lib/python2.7/dist-packages/django/forms/models.py" in choice
      904.         return (self.field.prepare_value(obj), self.field.label_from_instance(obj))
    File "/usr/local/lib/python2.7/dist-packages/django/forms/models.py" in label_from_instance
      955.         return smart_unicode(obj)
    File "/usr/local/lib/python2.7/dist-packages/django/utils/encoding.py" in smart_unicode
      39.     return force_unicode(s, encoding, strings_only, errors)
    File "/usr/local/lib/python2.7/dist-packages/django/utils/encoding.py" in force_unicode
      66.                 s = unicode(s)

    Exception Type: TemplateSyntaxError at /admin/ps/ps/add/
    Exception Value: Caught TypeError while rendering: coercing to Unicode: need string or buffer, NoneType found

解決方法は?

このエラーは __unicode__ メソッドが、入力されていないフィールドを返している場合。空白のフィールドは None であり、Pythonは None というエラーが出ます。

あなたの場合、ほとんどの場合、問題は PCE モデルの __unicode__ メソッド、特にその返すフィールドを指定します。

デフォルト値を返すことで、これを防ぐことができます。

def __unicode__(self):
   return self.some_field or u'None'