When using polymodels - forms give error 'XXX' object has no attribute 'class'

[GoogleCodeExporter]

What steps will reproduce the problem?
1. create a base model that inherits from polymodel.PolyModel 
2. create a subclass of the base model
3. create a ModelForm that uses the subclass
4. Try to display the form or use the admin interface

What is the expected output? What do you see instead?
'XXX' object has no attribute 'class'

What version of the product are you using? On what operating system?
lastest version on osx

Please provide any additional information below.

If I use exclude = [ 'class' ] in the form meta: it will work

Original issue reported on code.google.com by tommytastic on 21 Apr 2009 at 11:29

[GoogleCodeExporter]

Could you please try with the latest repo version? I'm too busy to code up the 
tests,
right now...

Original comment by wkornew...@gmail.com on 22 Apr 2009 at 9:26

[GoogleCodeExporter]

So, does it work?

Original comment by wkornew...@gmail.com on 24 Apr 2009 at 9:47

[GoogleCodeExporter]

Hi, Great to hear you have made a fix. Unfortunately I've got a bit stuck 
trying to
test. I originally started developing my app based on the sample app you have 
provided.

So today, I downloaded the latest sample app - I notice it uses django-1.1 now.

When I try to start that, I get the following error:

(I'm running on mac osx 10.5.6)

$ python manage.py runserver 8001

WARNING:root:Could not read datastore data from
/var/folders/hE/hEG11sliHkq0hizsuH4Zg++++TI/-Tmp-/django_aep-sample.datastore
WARNING:root:Could not read datastore data from
/var/folders/hE/hEG11sliHkq0hizsuH4Zg++++TI/-Tmp-/django_aep-sample.datastore.hi
story
Traceback (most recent call last):
  File "manage.py", line 4, in <module>
    setup_env(manage_py_env=True)
  File "/Users/tom/svn/aep/appenginepatch-sample/common/appenginepatch/aecmd.py",
line 63, in setup_env
    patch_all()
  File
"/Users/tom/svn/aep/appenginepatch-sample/common/appenginepatch/appenginepatcher
/patch.py",
line 21, in patch_all
    patch_django()
  File
"/Users/tom/svn/aep/appenginepatch-sample/common/appenginepatch/appenginepatcher
/patch.py",
line 588, in patch_django
    from ragendja import template
  File
"/Users/tom/svn/aep/appenginepatch-sample/common/appenginepatch/ragendja/templat
e.py", line
74, in <module>
    add_to_builtins(lib)
  File "/Users/tom/svn/aep/appenginepatch-sample/__init__.py", line 959, in
add_to_builtins

  File "/Users/tom/svn/aep/appenginepatch-sample/__init__.py", line 948, in get_library

  File
"/Users/tom/svn/aep/appenginepatch-sample/common/zip-packages/django-1.1.zip/dja
ngo/utils/importlib.py",
line 35, in import_module
  File
"/Users/tom/svn/aep/appenginepatch-sample/common/appenginepatch/ragendja/templat
etags/ragendjatags.py",
line 8, in <module>
    from ragendja.dbutils import prefetch_references
  File
"/Users/tom/svn/aep/appenginepatch-sample/common/appenginepatch/ragendja/dbutils
.py",
line 4, in <module>
    from django.utils import simplejson
  File "/Users/tom/svn/aep/appenginepatch-sample/__init__.py", line 111, in <module>

  File "/Users/tom/svn/aep/appenginepatch-sample/__init__.py", line 108, in <module>

  File
"/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-de
fault.bundle/Contents/Resources/google_appengine/google/appengine/dist/py_zipimp
ort.py",
line 213, in load_module
    exec code in mod.__dict__
  File
"/Library/Python/2.5/site-packages/simplejson-2.0.9-py2.5-macosx-10.5-i386.egg/s
implejson/decoder.py",
line 7, in <module>
  File
"/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-de
fault.bundle/Contents/Resources/google_appengine/google/appengine/dist/py_zipimp
ort.py",
line 213, in load_module
    exec code in mod.__dict__
  File
"/Library/Python/2.5/site-packages/simplejson-2.0.9-py2.5-macosx-10.5-i386.egg/s
implejson/scanner.py",
line 5, in <module>
  File
"/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-de
fault.bundle/Contents/Resources/google_appengine/google/appengine/dist/py_zipimp
ort.py",
line 213, in load_module
    exec code in mod.__dict__
  File
"/Library/Python/2.5/site-packages/simplejson-2.0.9-py2.5-macosx-10.5-i386.egg/s
implejson/_speedups.py",
line 7, in <module>
  File
"/Library/Python/2.5/site-packages/simplejson-2.0.9-py2.5-macosx-10.5-i386.egg/s
implejson/_speedups.py",
line 4, in __bootstrap__
  File
"/Library/Python/2.5/site-packages/setuptools-0.6c9-py2.5.egg/pkg_resources.py",
 line
841, in resource_filename
    self, resource_name
  File
"/Library/Python/2.5/site-packages/setuptools-0.6c9-py2.5.egg/pkg_resources.py",
 line
1311, in get_resource_filename
    return self._extract_resource(manager, zip_path)
  File
"/Library/Python/2.5/site-packages/setuptools-0.6c9-py2.5.egg/pkg_resources.py",
 line
1342, in _extract_resource
    os.write(outf, self.loader.get_data(zip_path))
  File
"/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-de
fault.bundle/Contents/Resources/google_appengine/google/appengine/dist/py_zipimp
ort.py",
line 226, in get_data
    (fullpath, required_prefix))
IOError: Path 'simplejson/_speedups.so' doesn't start with zipfile name
'/Library/Python/2.5/site-packages/simplejson-2.0.9-py2.5-macosx-10.5-i386.egg/'

I was going to copy my app into here to test. 

Or.. should I be using downloading just the 'django-app-engine-dev' repo, 
zipping it
and replacing my existing django-1.02.zip in zip-files?

Thanks

Original comment by tommytastic on 24 Apr 2009 at 1:43

[GoogleCodeExporter]

I guess you'll have to remove your simplejson package because that isn't 
compatible
with App Engine. As an alternative, you could add a simplejson.py file to your
"common" folder which contains simply this line:

raise ImportError("Only Django's internal simplejson package is supported!")

Original comment by wkornew...@gmail.com on 24 Apr 2009 at 5:47

[GoogleCodeExporter]

Hmm I see - I wonder why I wasn't getting the error previously. 
Managed to get it going again, removed my hacks to 'exclude' class fields and it
works! So your fix seems to be doing the trick . Will keep an eye on it and 
report
back. Entering another issue regarding FromWithSets and 'initial' values.

Original comment by tommytastic on 24 Apr 2009 at 9:54

[GoogleCodeExporter]

Great! :)

Original comment by wkornew...@gmail.com on 24 Apr 2009 at 10:18

• Changed state: Fixed

[GoogleCodeExporter]

I have the same problem with appengine 1.2.5. 
My Models and ModelForms are in external module named modules.py
Although I add the line "exclude = [ 'class' ]" in my ModelForm it not works.

Original comment by big...@gmail.com on 30 Sep 2009 at 1:28

[GoogleCodeExporter]

I had to back out of using polymodel in my django on app engine application as 
well. 
I would get the same django form error on the base or subclass model. I 
couldn't 
find an answer on line on how to get django to ignore 'class' in the models 
returned 
from the datastore.  

Original comment by SCBoe...@gmail.com on 25 Jan 2010 at 8:00

[GoogleCodeExporter]

This issue is not fixed (this is with r102 from SVN):

==== models.py 
from google.appengine.ext import db 
from google.appengine.ext.db import polymodel 
class Person(polymodel.PolyModel): 
  first_name = db.StringProperty() 
  last_name = db.StringProperty() 
  dob = db.DateProperty(verbose_name="Date of Birth") 
class Adult(Person): 
  interests = db.StringListProperty() 
==== views.py 
import logging 
from google.appengine.ext import db 
from django import forms 
from google.appengine.ext.db import djangoforms 
from django.http import HttpResponseRedirect 
from django.shortcuts import render_to_response 
from testing import models 
class AdultForm(djangoforms.ModelForm): 
  class Meta: 
    model = models.Adult 
    exclude = ( 'class', 'create_ts', 'modify_ts', 'edited_by', ) 
def adult_form(request, person_id=None): 
  if request.method == 'POST': 
    if person_id: 
      # update an existing person with data from the form 
      adult = models.Adult.get_by_id(int(person_id)) 
      form = AdultForm(request.POST, instance=adult) 
    else: 
      # create a new person solely from the form data 
      form = AdultForm(request.POST) 
    if form.is_valid(): 
      # django doesn't know how to commit to gae 
      adult = form.save(commit=False) 
      adult.put() 
      return HttpResponseRedirect('/') 
  else: 
    if person_id: 
      # new form filled out with existing data 
      adult = models.Adult.get_by_id(int(person_id)) 
      form = AdultForm(instance=adult) 
    else: 
      # new, empty form 
      form = AdultForm() 
  return render_to_response('adult_form.html', { 
    'person_id': person_id, 
    'form': form, 
  }) 
==== 
Environment: 
Request Method: GET 
Request URL: http://localhost:8080/testing/10 
Django Version: 1.1.1 
Python Version: 2.5.5 
Installed Applications: 
('appengine_django',) 
Installed Middleware: 
('django.middleware.common.CommonMiddleware',) 
Traceback: 
File "/opt/local/lib/python2.5/site-packages/django/core/handlers/ 
base.py" in get_response 
  92.                 response = callback(request, *callback_args, 
**callback_kwargs) 
File "/Users/b/src/bepreparedapp/testing/views.py" in adult_form 
  38.       form = AdultForm(instance=adult) 
File "/Users/b/Applications/Developer/GoogleAppEngineLauncher.app/ 
Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/ 
google_appengine/google/appengine/ext/db/djangoforms.py" in __init__ 
  753.         object_data[name] = prop.get_value_for_form(instance) 
File "/Users/b/Applications/Developer/GoogleAppEngineLauncher.app/ 
Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/ 
google_appengine/google/appengine/ext/db/djangoforms.py" in 
get_value_for_form 
  191.     return getattr(instance, self.name) 
Exception Type: AttributeError at /testing/10 
Exception Value: 'Adult' object has no attribute 'class' 

Original comment by benjamin...@gmail.com on 14 Apr 2010 at 8:50

[GoogleCodeExporter]

A workaround, found on the main google-appengine list ('djangoforms.ModelForm 
for PolyModel ??', Oct 09), 
is to exclude the '_class' attribute (not 'class').

e.g. for my previous example:

class AdultForm(djangoforms.ModelForm):
  class Meta:
    model = models.Adult
    exclude = ( '_class', 'create_ts', 'modify_ts', 'edited_by', )

Original comment by benjamin...@gmail.com on 14 Apr 2010 at 9:14