#18463: Using len() in Paginator object can raise an error
------------------------------+------------------------------------
Reporter: renato@… | Owner: claudep
Type: Bug | Status: assigned
Component: Core (Other) | Version: master
Severity: Normal | Resolution:
Keywords: | Triage Stage: Accepted
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
------------------------------+------------------------------------
Changes (by claudep):
* status: new => assigned
* needs_better_patch: => 0
* needs_tests: => 0
* owner: nobody => claudep
* needs_docs: => 0
* stage: Unreviewed => Accepted
Old description:
> I'm getting the following error if I try to run a piece of code through
> my views.py:
>
> Traceback (most recent call last):
> File "<console>", line 1, in <module>
> File "/home/mp/webapps/django/rep/app/views.py", line 331, in
> search_species
> print len(recs)
> File "/home/mp/webapps/django/lib/python2.7/django/core/paginator.py",
> line 88, in __len__
> return len(self.object_list)
> File "/home/mp/webapps/django/lib/python2.7/django/db/models/query.py",
> line 87, in __len__
> self._result_cache = list(self.iterator())
> File "/home/mp/webapps/django/lib/python2.7/django/db/models/query.py",
> line 284, in iterator
> model_cls = deferred_class_factory(self.model, skip)
> File
> "/home/mp/webapps/django/lib/python2.7/django/db/models/query_utils.py",
> line 180, in deferred_class_factory
> return type(name, (model,), overrides)
> TypeError: type() argument 1 must be string, not unicode
>
> Strangely, if I run a similar code directly in the Django shell,
> everything goes well. The code looks like this:
>
> {{{
> from app.models import MyClass
> qs = MyClass.objects.all()
> from django.core.paginator import Paginator
> paginator = Paginator(qs, 25)
> recs = paginator.page(1)
> print len(recs)
> }}}
>
> So you have to run this code through a method in views.py to get a crash
> in the last line.
>
> I'm afraid I have no idea of what's going on and how to properly fix
> this, but if I change the offending line from the traceback by forcing
> str() in the name parameter it works:
>
> {{{
> return type(str(name), (model,), overrides)
> }}}
New description:
I'm getting the following error if I try to run a piece of code through my
views.py:
{{{
Traceback (most recent call last):
File "<console>", line 1, in <module>
File "/home/mp/webapps/django/rep/app/views.py", line 331, in
search_species
print len(recs)
File "/home/mp/webapps/django/lib/python2.7/django/core/paginator.py",
line 88, in __len__
return len(self.object_list)
File "/home/mp/webapps/django/lib/python2.7/django/db/models/query.py",
line 87, in __len__
self._result_cache = list(self.iterator())
File "/home/mp/webapps/django/lib/python2.7/django/db/models/query.py",
line 284, in iterator
model_cls = deferred_class_factory(self.model, skip)
File
"/home/mp/webapps/django/lib/python2.7/django/db/models/query_utils.py",
line 180, in deferred_class_factory
return type(name, (model,), overrides)
TypeError: type() argument 1 must be string, not unicode
}}}
Strangely, if I run a similar code directly in the Django shell,
everything goes well. The code looks like this:
{{{
from app.models import MyClass
qs = MyClass.objects.all()
from django.core.paginator import Paginator
paginator = Paginator(qs, 25)
recs = paginator.page(1)
print len(recs)
}}}
So you have to run this code through a method in views.py to get a crash
in the last line.
I'm afraid I have no idea of what's going on and how to properly fix this,
but if I change the offending line from the traceback by forcing str() in
the name parameter it works:
{{{
return type(str(name), (model,), overrides)
}}}
--
Comment:
This bug is only triggered when the model name in deferred_class_factory
is truncated (> 80 chars) and then a Unicode string is returned. Calling
str() seems a good solution.
--
Ticket URL: <https://code.djangoproject.com/ticket/18463#comment:1>
Django <https://code.djangoproject.com/>
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