[Replying to your first message rather than your last because this is the
one with a traceback showing why this problem is happening. See comments
inline in the traceback.]
On Wed, Apr 22, 2009 at 9:33 AM, robin <robinc...@gmail.com> wrote:
>
> I have an unexplainable problem involving importing from 3 apps and
> one python script.
> Thank you to those who took the time to understand this problem.
>
> Sorry I cannot explain this problem, I tried to make it as simple as
> possible below.
>
> 'acc' has many 'numbers' which has a one-to-one relationship with
> 'two'.
>
> 'python run.py' tries to import from 'numbers' but causes import
> errors when 'acc' modelchoicefield queryset changes from 'all' to
> 'filter'
>
> ----------------acc/models.py--------------
>
> from django.db import models
> from django import forms
>
> class Group(models.Model):
> name=models.IntegerField()
>
> class User(models.Model):
> group=models.ForeignKey(Group)
>
> class UserForm(forms.ModelForm):
> group=forms.ModelChoiceField(Group.objects.all()) #causes problem if
> changed to Group.objects.filter(name='blah')
> class Meta:
> model=User
>
> ----------------number/models.py------------
>
> from django.db import models
> from acc.models import User
>
> class Number(models.Model):
> name=models.IntegerField()
>
> -------------------two/models.py-----------------
>
> from django.db import models
> from numbers.models import Number
>
> class Two(models.Model):
> number=models.OneToOneField(Number,primary_key=True) #potential
> problem line
>
> ---------------run.py-----------------------
>
> #!/usr/bin/env python
> from django.core.management import setup_environ
> import settings
> setup_environ(settings)
> from numbers.models import Number
>
> #######PROBLEM-#######
>
> With the above setup, if i execute: python run.py, it should be fine.
> BUT the problem occurs the moment i change acc.models from:
>
> group=forms.ModelChoiceField(Group.objects.all())
> #TO#
> group=forms.ModelChoiceField(Group.objects.filter(name='blah'))
>
> The last error it will show is:
>
> File "/home/robin/test/toast/two/models.py", line 2, in <module>
> from numbers.models import Number
> ImportError: cannot import name Number
>
>
> Thanks a lot,
> Robin
>
>
> The complete errors are below:
>
> Traceback (most recent call last):
> File "expire_listing.py", line 6, in <module>
> from numbers.models import Number
It all starts with attempting to import Number from numbers.models...
>
> File "/home/robin/test/toast/numbers/models.py", line 2, in <module>
> from acc.models import User
which leads to needing to import User from acc.models...
>
> File "/home/robin/test/toast/acc/models.py", line 11, in <module>
> class UserForm(forms.ModelForm):
and acc.models contains a UserForm class definition...
>
> File "/home/robin/test/toast/acc/models.py", line 12, in UserForm
> group=forms.ModelChoiceField(Group.objects.filter(name__in=[0,1]))
which includes a Group.objects.filter() call. filter() has a bit of work to
do...
>
> File "/usr/lib/python2.5/site-packages/django/db/models/manager.py",
> line 102, in filter
> return self.get_query_set().filter(*args, **kwargs)
> File "/usr/lib/python2.5/site-packages/django/db/models/query.py",
> line 489, in filter
> return self._filter_or_exclude(False, *args, **kwargs)
> File "/usr/lib/python2.5/site-packages/django/db/models/query.py",
> line 507, in _filter_or_exclude
> clone.query.add_q(Q(*args, **kwargs))
> File "/usr/lib/python2.5/site-packages/django/db/models/sql/
> query.py", line 1258, in add_q
> can_reuse=used_aliases)
> File "/usr/lib/python2.5/site-packages/django/db/models/sql/
> query.py", line 1133, in add_filter
> negate=negate, process_extras=process_extras)
> File "/usr/lib/python2.5/site-packages/django/db/models/sql/
> query.py", line 1309, in setup_joins
> field, model, direct, m2m = opts.get_field_by_name(name)
> File "/usr/lib/python2.5/site-packages/django/db/models/options.py",
> line 281, in get_field_by_name
> cache = self.init_name_map()
> File "/usr/lib/python2.5/site-packages/django/db/models/options.py",
> line 311, in init_name_map
> for f, model in self.get_all_related_m2m_objects_with_model():
> File "/usr/lib/python2.5/site-packages/django/db/models/options.py",
> line 388, in get_all_related_m2m_objects_with_model
> cache = self._fill_related_many_to_many_cache()
> File "/usr/lib/python2.5/site-packages/django/db/models/options.py",
> line 402, in _fill_related_many_to_many_cache
> for klass in get_models():
> File "/usr/lib/python2.5/site-packages/django/db/models/loading.py",
> line 136, in get_models
> self._populate()
> File "/usr/lib/python2.5/site-packages/django/db/models/loading.py",
> line 57, in _populate
> self.load_app(app_name, True)
which eventually requires ensuring that your app is loaded...
>
> File "/usr/lib/python2.5/site-packages/django/db/models/loading.py",
> line 72, in load_app
> mod = __import__(app_name, {}, {}, ['models'])
> File "/home/robin/test/toast/two/models.py", line 2, in <module>
> from numbers.models import Number
> ImportError: cannot import name Number
which comes full circle back to attempting to import Number from
numbers.models. But Python is already in the middle of attempting to import
Number from numbers.models so if it didn't bail out here with an error you'd
just get infinite recursion.
So you've run into trouble because you've put something -- the form
definition for your UserForm -- which requires your app's models to be fully
loaded, in a place where Python is going to attempt to execute it before all
of your app's models have been loaded. I think a better solution than the
one you list in your last note (which I don't quite follow, actually), is to
move your form definitons out of your models files. That way loading your
models won't trigger trying to do something that needs all of your models to
be loaded first.
Karen
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