Unicodeへの強制：文字列またはバッファが必要、Django adminでのレンダリング時にNoneTypeが見つかりました
私は長い間このエラーを抱えていますが、理解できません：
レンダリング中にTypeErrorをキャッチ：Unicodeへの強制：文字列またはバッファーが必要、NoneTypeが見つかりました
モデルのいずれかを追加または変更しようとすると、管理者で発生します（表示は正常に動作します）
これはモデルです：
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')
ここで何が間違っていますか？
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
このエラーは、入力されていないフィールドを返す__unicode__メソッドがある場合に発生します。空白のフィールドはNoneであり、PythonはNoneを変換できないため、エラーが発生します。
あなたの場合、問題はおそらくPCEモデルの__unicode__メソッド、具体的にはそれが返すフィールドにあります。
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'
このエラーは、__unicode__メソッドで文字列の代わりにオブジェクトを返すときに発生する可能性があります。例えば：
class Author(models.Model):
. . .
name = models.CharField(...)
class Book(models.Model):
. . .
author = models.ForeignKey(Author, ...)
. . .
def __unicode__(self):
return self.author # <<<<<<<< this causes problems
このエラーを回避するには、作成者インスタンスをUnicodeにキャストできます。
class Book(models.Model):
. . .
def __unicode__(self):
return unicode(self.author) # <<<<<<<< this is OK
私の場合、それは別のものでした：保存しているオブジェクトは、何らかの種類の関係を設定する前に、まずidを持っている必要があります（たとえば、save（）を呼び出す必要があります）。
以前の機能を提供された機能に置き換えます。最も簡単な解決策は次のとおりです。
def __unicode__(self):
return unicode(self.nom_du_site)
戻り値def __unicode __は、Django管理パネルで「some_field」を正しく表示するために、関連するモデル（テーブル）の戻り値に類似している必要があります。以下も使用できます。
def __str__(self):
return self.some_field