Python-Metaklasse und Vererbung – Attribute nicht erkannt (django-tables2) ⇐ Python

[Anonymous]

Ich versuche, eine UsersTable-Klasse mit django-tables2 zu schreiben, die von StudentsTable in Unterklassen unterteilt werden soll. Dieser Code funktioniert einwandfrei:
tables.py
import django_tables2 as tables
from django_tables2.utils import A # alias for accessor
from .models.environment import Student

def getEditColumn(accessor, kwargs):
return tables.LinkColumn(
viewname='wakemeup:edit_object',
kwargs=kwargs,
verbose_name='',
text='Editar',
accessor=accessor
)

class UsersTable(tables.Table):

# Define constructor
def __init__(self, *args, **kwargs):
# Call base table class constructor
super(UsersTable, self).__init__(data = kwargs['data'])

objectid = kwargs['objectid']
objecttype = kwargs['objecttype']

# Create base attributes
self.objectid = objectid
self.objecttype = objecttype

self.mykwargs={
'objecttype': objecttype,
'objectid': A(objectid)
}

self.edit_link = getEditColumn(objectid, self.mykwargs)

class Meta:
model = Student

class StudentsTable(UsersTable):

# Call UsersTable constructor
def __init__(self, *args, **kwargs):
super(StudentsTable, self).__init__(*args, **kwargs)
print(self.edit_link) # Verify edit_link has been generated

class Meta:
sequence = ('firstname','lastname','emailaddress','phonenumber','defaultsignaturescanfile','classid')

Wenn ich jedoch versuche, auf die von UsersTable geerbte Spalte edit_link zu verweisen, erhalte ich eine Fehlermeldung:
< strong>Geänderte StudentsTable
class StudentsTable(UsersTable):

# Call UsersTable constructor
def __init__(self, *args, **kwargs):
super(StudentsTable, self).__init__(*args, **kwargs)
print(self.edit_link) # Verify edit_link has been generated

class Meta:
exclude = ('studentuserid','reputationvalue','schoolid')
sequence = ('firstname','lastname','emailaddress','phonenumber','defaultsignaturescanfile','classid','edit_link')

Fehler
Exception Type: KeyError
Exception Value: 'edit_link'

Es scheint, als würden die Metaklasseninformationen gelesen, bevor die geerbte Spalte „edit_link“ generiert wird. Die print(edit_link)-Zeile gibt das erwartete Objekt zurück, sodass das Feld verfügbar ist.
Ich habe alle möglichen Versuche mit der Meta-Klasse ausprobiert ... aber kein Erfolg. Kann mir bitte jemand helfen?
Bearbeiten
Hier ist die Spur:
Environment:

Request Method: GET
Request URL: http://127.0.0.1:8000/wakemeup/admin/student

Django Version: 2.0.1
Python Version: 3.6.4
Installed Applications:
['django.contrib.auth',
'django.contrib.contenttypes',
'django.contrib.sessions',
'django.contrib.messages',
'django.contrib.staticfiles',
'users.apps.UsersConfig',
'wakemeup.apps.WakemeupConfig',
'crispy_forms',
'django_tables2']
Installed Middleware:
('whitenoise.middleware.WhiteNoiseMiddleware',
'django.middleware.security.SecurityMiddleware',
'django.contrib.sessions.middleware.SessionMiddleware',
'django.middleware.common.CommonMiddleware',
'django.middleware.csrf.CsrfViewMiddleware',
'django.contrib.auth.middleware.AuthenticationMiddleware',
'django.contrib.messages.middleware.MessageMiddleware',
'django.middleware.clickjacking.XFrameOptionsMiddleware')

Template error:
In template C:\Program Files (x86)\Python36-32\lib\site-packages\django_tables2\templates\django_tables2\bootstrap.html, error at line 11
edit_link
1 : {% load django_tables2 %}
2 : {% load i18n %}
3 : {% block table-wrapper %}
4 :
5 : {% block table %}
6 :
7 : {% block table.thead %}
8 : {% if table.show_header %}
9 :
10 :
11 : {% for column in table.columns %}
12 : {% if column.orderable %}
13 : {{ column.header }}
14 : {% else %}
15 : {{ column.header }}
16 : {% endif %}
17 : {% endfor %}
18 :
19 :
20 : {% endif %}
21 : {% endblock table.thead %}

Traceback:

File "C:\Program Files (x86)\Python36-32\lib\site-packages\django\core\handlers\exception.py" in inner
35. response = get_response(request)

File "C:\Program Files (x86)\Python36-32\lib\site-packages\django\core\handlers\base.py" in _get_response
128. response = self.process_exception_by_middleware(e, request)

File "C:\Program Files (x86)\Python36-32\lib\site-packages\django\core\handlers\base.py" in _get_response
126. response = wrapped_callback(request, *callback_args, **callback_kwargs)

File "c:\Users\ravioli\eclipse-workspace\dcp\wakemeup\views.py" in admin_list
100. return render(request, 'wakemeup/admin/index.html', {'objects' : objectSet, 'objecttype': objecttype})

File "C:\Program Files (x86)\Python36-32\lib\site-packages\django\shortcuts.py" in render
36. content = loader.render_to_string(template_name, context, request, using=using)

File "C:\Program Files (x86)\Python36-32\lib\site-packages\django\template\loader.py" in render_to_string
62. return template.render(context, request)

File "C:\Program Files (x86)\Python36-32\lib\site-packages\django\template\backends\django.py" in render
61. return self.template.render(context)

File "C:\Program Files (x86)\Python36-32\lib\site-packages\django\template\base.py" in render
175. return self._render(context)

File "C:\Program Files (x86)\Python36-32\lib\site-packages\django\template\base.py" in _render
167. return self.nodelist.render(context)

File "C:\Program Files (x86)\Python36-32\lib\site-packages\django\template\base.py" in render
943. bit = node.render_annotated(context)

File "C:\Program Files (x86)\Python36-32\lib\site-packages\django\template\base.py" in render_annotated
910. return self.render(context)

File "C:\Program Files (x86)\Python36-32\lib\site-packages\django\template\loader_tags.py" in render
155. return compiled_parent._render(context)

File "C:\Program Files (x86)\Python36-32\lib\site-packages\django\template\base.py" in _render
167. return self.nodelist.render(context)

File "C:\Program Files (x86)\Python36-32\lib\site-packages\django\template\base.py" in render
943. bit = node.render_annotated(context)

File "C:\Program Files (x86)\Python36-32\lib\site-packages\django\template\base.py" in render_annotated
910. return self.render(context)

File "C:\Program Files (x86)\Python36-32\lib\site-packages\django\template\loader_tags.py" in render
67. result = block.nodelist.render(context)

File "C:\Program Files (x86)\Python36-32\lib\site-packages\django\template\base.py" in render
943. bit = node.render_annotated(context)

File "C:\Program Files (x86)\Python36-32\lib\site-packages\django\template\base.py" in render_annotated
910. return self.render(context)

File "C:\Program Files (x86)\Python36-32\lib\site-packages\django\template\loader_tags.py" in render
67. result = block.nodelist.render(context)

File "C:\Program Files (x86)\Python36-32\lib\site-packages\django\template\base.py" in render
943. bit = node.render_annotated(context)

File "C:\Program Files (x86)\Python36-32\lib\site-packages\django\template\base.py" in render_annotated
910. return self.render(context)

File "C:\Program Files (x86)\Python36-32\lib\site-packages\django_tables2\templatetags\django_tables2.py" in render
169. return template.render(context={'table': table}, request=request)

File "C:\Program Files (x86)\Python36-32\lib\site-packages\django\template\backends\django.py" in render
61. return self.template.render(context)

File "C:\Program Files (x86)\Python36-32\lib\site-packages\django\template\base.py" in render
175. return self._render(context)

File "C:\Program Files (x86)\Python36-32\lib\site-packages\django\template\base.py" in _render
167. return self.nodelist.render(context)

File "C:\Program Files (x86)\Python36-32\lib\site-packages\django\template\base.py" in render
943. bit = node.render_annotated(context)

File "C:\Program Files (x86)\Python36-32\lib\site-packages\django\template\base.py" in render_annotated
910. return self.render(context)

File "C:\Program Files (x86)\Python36-32\lib\site-packages\django\template\loader_tags.py" in render
155. return compiled_parent._render(context)

File "C:\Program Files (x86)\Python36-32\lib\site-packages\django\template\base.py" in _render
167. return self.nodelist.render(context)

File "C:\Program Files (x86)\Python36-32\lib\site-packages\django\template\base.py" in render
943. bit = node.render_annotated(context)

File "C:\Program Files (x86)\Python36-32\lib\site-packages\django\template\base.py" in render_annotated
910. return self.render(context)

File "C:\Program Files (x86)\Python36-32\lib\site-packages\django\template\loader_tags.py" in render
67. result = block.nodelist.render(context)

File "C:\Program Files (x86)\Python36-32\lib\site-packages\django\template\base.py" in render
943. bit = node.render_annotated(context)

File "C:\Program Files (x86)\Python36-32\lib\site-packages\django\template\base.py" in render_annotated
910. return self.render(context)

File "C:\Program Files (x86)\Python36-32\lib\site-packages\django\template\loader_tags.py" in render
67. result = block.nodelist.render(context)

File "C:\Program Files (x86)\Python36-32\lib\site-packages\django\template\base.py" in render
943. bit = node.render_annotated(context)

File "C:\Program Files (x86)\Python36-32\lib\site-packages\django\template\base.py" in render_annotated
910. return self.render(context)

File "C:\Program Files (x86)\Python36-32\lib\site-packages\django\template\base.py" in render
993. output = self.filter_expression.resolve(context)

File "C:\Program Files (x86)\Python36-32\lib\site-packages\django\template\base.py" in resolve
676. obj = self.var.resolve(context)

File "C:\Program Files (x86)\Python36-32\lib\site-packages\django\template\base.py" in resolve
802. value = self._resolve_lookup(context)

File "C:\Program Files (x86)\Python36-32\lib\site-packages\django\template\base.py" in _resolve_lookup
864. current = current()

File "C:\Program Files (x86)\Python36-32\lib\site-packages\django\template\loader_tags.py" in super
81. return mark_safe(self.render(self.context))

File "C:\Program Files (x86)\Python36-32\lib\site-packages\django\template\loader_tags.py" in render
67. result = block.nodelist.render(context)

File "C:\Program Files (x86)\Python36-32\lib\site-packages\django\template\base.py" in render
943. bit = node.render_annotated(context)

File "C:\Program Files (x86)\Python36-32\lib\site-packages\django\template\base.py" in render_annotated
910. return self.render(context)

File "C:\Program Files (x86)\Python36-32\lib\site-packages\django\template\loader_tags.py" in render
67. result = block.nodelist.render(context)

File "C:\Program Files (x86)\Python36-32\lib\site-packages\django\template\base.py" in render
943. bit = node.render_annotated(context)

File "C:\Program Files (x86)\Python36-32\lib\site-packages\django\template\base.py" in render_annotated
910. return self.render(context)

File "C:\Program Files (x86)\Python36-32\lib\site-packages\django\template\defaulttags.py" in render
314. return nodelist.render(context)

File "C:\Program Files (x86)\Python36-32\lib\site-packages\django\template\base.py" in render
943. bit = node.render_annotated(context)

File "C:\Program Files (x86)\Python36-32\lib\site-packages\django\template\base.py" in render_annotated
910. return self.render(context)

File "C:\Program Files (x86)\Python36-32\lib\site-packages\django\template\defaulttags.py" in render
168. len_values = len(values)

File "C:\Program Files (x86)\Python36-32\lib\site-packages\django_tables2\columns\base.py" in __len__
686. return len(self.visible())

File "C:\Program Files (x86)\Python36-32\lib\site-packages\django_tables2\columns\base.py" in visible
643. return list(self.itervisible())

File "C:\Program Files (x86)\Python36-32\lib\site-packages\django_tables2\columns\base.py" in
640. return (x for x in self.iterall() if x.visible)

File "C:\Program Files (x86)\Python36-32\lib\site-packages\django_tables2\columns\base.py" in
597. return (column for name, column in self.iteritems())

File "C:\Program Files (x86)\Python36-32\lib\site-packages\django_tables2\columns\base.py" in iteritems
614. yield (name, self.columns[name])

Exception Type: KeyError at /wakemeup/admin/student
Exception Value: 'edit_link'