ForeignKey related bug
Hi,
While building a blog type application, I seem to have stumbled upon a
bug. In a nut shell all object attributes have become read only when I
fetch the object from a query set which is fetched using the xxx_set()
API.
Please see the pdb trace for details. I have added comments to depict
the erroneous logs. (pdb was started from within a unit test). I do
get similar behavior when using the shell.
Any suggestions for debugging this one?
regards,
CP
class Blog (models.Model):
title = models.CharField (maxlength = 300, default=None)
blog_id = models.CharField (unique=True, null=False, blank=False,
default=None, maxlength=64)
class Post (models.Model):
blog = models.ForeignKey (Blog)
post_id = models.CharField (maxlength = 64, null=False,
unique=True)
title = models.CharField (maxlength = 200, null=False)
pdb logs
-
(Pdb) blog.post_set.all()
[]
(Pdb) m = blog.post_set.all()
(Pdb) m[0].title
'check accidents'
(Pdb) print m[0]
Blogger Post id: 6497585470310212022, title: check accidents
(Pdb) m[0].title = "dfdf"
(Pdb) m[0].title #NOTE: that the title does not change
'check accidents'
(Pdb) print m[0]
Blogger Post id: 6497585470310212022, title: check accidents
(Pdb) m[0].__dict__
{'blog_id': 2, 'title': 'check accidents',
'post_id': '6497585470310212022', 'id': 1}
(Pdb) m[0].__dict__["title"] = "dfdf"
(Pdb) m[0].__dict__
{'blog_id': 2, 'title': 'check accidents',
'post_id': '6497585470310212022', 'id': 1}
(Pdb) ps = Post.objects.all()
(Pdb) ps
[]
(Pdb) ps[0].title = "dfdF"
(Pdb) ps
[]
(Pdb)
python logs
---
>>> blog = Blog.objects.get (url__contains = "abc")
>>> m = blog.post_set.all()
>>> m[0].title
'FDfdF'
>>> m[0].title="dfdF"
>>> m[0]
>>> m[0].title
'FDfdF'
--~--~-~--~~~---~--~~
You received this message because you are subscribed to the Google Groups
"Django users" group.
To post to this group, send email to django-users@googlegroups.com
To unsubscribe from this group, send email to [EMAIL PROTECTED]
For more options, visit this group at
http://groups.google.com/group/django-users?hl=en
-~--~~~~--~~--~--~---
Re: ForeignKey related bug
Chirayu Patel wrote: > Hi, > > While building a blog type application, I seem to have stumbled upon a > bug. In a nut shell all object attributes have become read only when I > fetch the object from a query set which is fetched using the xxx_set() > API. > > Please see the pdb trace for details. I have added comments to depict > the erroneous logs. (pdb was started from within a unit test). I do > get similar behavior when using the shell. > > Any suggestions for debugging this one? This may not be all of your problem, but pdb had a bug (at least Python 2.4, maybe it's gone in 2.5) wherein setting a variable at a breakpoint worked if and only if you didn't reexamine it after setting it. E.g., this worked: (Pdb) foobar = "dfdf" (Pdb) c But this did not: (Pdb) foobar = "dfdf" (Pdb) foobar 'old value' (Pdb) c There used to be a post on someone's blog about this, but darned if I can find it now. John --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups "Django users" group. To post to this group, send email to django-users@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/django-users?hl=en -~--~~~~--~~--~--~---
Re: ForeignKey related bug
> > A little weird, maybe someone else can explain exactly what's going > on. Presumably a QuerySet slice is somehow not being treated as the > object itself. Hi, As Eric correctly pointed out that slicing a QuerySet is not "sticky". Whenever you take a slice of an exisiting QuerySet, Django clones it dynamically to a new QuerySet. So every time you reference m[0] you get a slice from a *clone* of the QuerySet m. It follows that this clone has a different instance of m[0] from the previous m[0]. As Eric suggested, save m[0] first to a variable if you need to act on a known single instance of that object for multiple operations. -Rajesh D --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups "Django users" group. To post to this group, send email to django-users@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/django-users?hl=en -~--~~~~--~~--~--~---
Re: ForeignKey related bug
> While building a blog type application, I seem to have stumbled upon a > bug. In a nut shell all object attributes have become read only when I > fetch the object from a query set which is fetched using the xxx_set() > API. Hi Chirayu, Looks like the problem is not the FOO_set() manager, but setting attributes on an object accessed via a QuerySet slice. Try putting m[0] by itself into a variable, and then setting attributes on that variable: it works. Directly setting attributes by using m[0].title = XXX doesn't seem to stick, however. x = m[0] x.title = 'dfdf' x.title # gets me u'dfdf' A little weird, maybe someone else can explain exactly what's going on. Presumably a QuerySet slice is somehow not being treated as the object itself. Eric --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups "Django users" group. To post to this group, send email to django-users@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/django-users?hl=en -~--~~~~--~~--~--~---
Re: ForeignKey related bug
> While building a blog type application, I seem to have stumbled upon a > bug. In a nut shell all object attributes have become read only when I > fetch the object from a query set which is fetched using the xxx_set() > API. Hi Chirayu, Looks like the problem is not the FOO_set() manager, but setting attributes on an object accessed via a QuerySet slice. Try putting m[0] by itself into a variable, and then setting attributes on that variable: it works. Directly setting attributes by using m[0].title = XXX doesn't seem to stick, however. x = m[0] x.title = 'dfdf' x.title # gets me u'dfdf' A little weird, maybe someone else can explain exactly what's going on. Presumably a QuerySet slice is somehow not being treated as the object itself. Eric --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups "Django users" group. To post to this group, send email to django-users@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/django-users?hl=en -~--~~~~--~~--~--~---
ForeignKey related bug
Hi,
While building a blog type application, I seem to have stumbled upon a
bug. In a nut shell all object attributes have become read only when I
fetch the object from a query set which is fetched using the xxx_set()
API.
Please see the pdb trace for details. I have added comments to depict
the erroneous logs. (pdb was started from within a unit test). I do
get similar behavior when using the shell.
Any suggestions for debugging this one?
regards,
CP
class Blog (models.Model):
title = models.CharField (maxlength = 300, default=None)
blog_id = models.CharField (unique=True, null=False, blank=False,
default=None, maxlength=64)
class Post (models.Model):
blog = models.ForeignKey (Blog)
post_id = models.CharField (maxlength = 64, null=False, unique=True)
title = models.CharField (maxlength = 200, null=False)
pdb logs
-
(Pdb) blog.post_set.all()
[]
(Pdb) m = blog.post_set.all()
(Pdb) m[0].title
'check accidents'
(Pdb) print m[0]
Blogger Post id: 6497585470310212022, title: check accidents
(Pdb) m[0].title = "dfdf"
(Pdb) m[0].title #NOTE: that the title does not change
'check accidents'
(Pdb) print m[0]
Blogger Post id: 6497585470310212022, title: check accidents
(Pdb) m[0].__dict__
{'blog_id': 2, 'title': 'check accidents',
'post_id': '6497585470310212022', 'id': 1}
(Pdb) m[0].__dict__["title"] = "dfdf"
(Pdb) m[0].__dict__
{'blog_id': 2, 'title': 'check accidents',
'post_id': '6497585470310212022', 'id': 1}
(Pdb) ps = Post.objects.all()
(Pdb) ps
[]
(Pdb) ps[0].title = "dfdF"
(Pdb) ps
[]
(Pdb)
python logs
---
>>> blog = Blog.objects.get (url__contains = "abc")
>>> m = blog.post_set.all()
>>> m[0].title
'FDfdF'
>>> m[0].title="dfdF"
>>> m[0]
>>> m[0].title
'FDfdF'
--~--~-~--~~~---~--~~
You received this message because you are subscribed to the Google Groups
"Django users" group.
To post to this group, send email to django-users@googlegroups.com
To unsubscribe from this group, send email to [EMAIL PROTECTED]
For more options, visit this group at
http://groups.google.com/group/django-users?hl=en
-~--~~~~--~~--~--~---
