Re: How to concatenate a list of Q objects?

[Tom M]

Just to explain

q = q | f if q else f

is using the short version of if/else, so let's expand that:

if q:
q = q | f
else:
q = f

q is only False when you have a Q object with no parameters i.e. Q()

and as you may have seen above | means OR. This is because the Q
object implements the __or__ special method.



On 7 Apr, 19:56, Daniel  wrote:
> Thanks alot guys.  If I can be honest, I'm having a little trouble
> digesting just this one line:
>
> q = q | f if q else f
>
> That line of code only allows (q1 | q2 | q3), right?
>
> It will not allow mixing "AND" as well as "OR" (i.e., q1 & q2 | q3)?
>
> Thanks!
>
> On Apr 7, 1:26 pm, Vinicius Mendes  wrote:
>
> > On Wed, Apr 7, 2010 at 2:00 PM, Tom Evans  wrote:
> > > On Wed, Apr 7, 2010 at 5:39 PM, Daniel  wrote:
> > > > Hi,
>
> > > > Thank you for your help everyone.  I know that I need to learn python
> > > > better, and I did read those articles.  What is still a bit unclear to
> > > > me, though, is how could I add an "OR" or "AND" separator between Q
> > > > objects?
>
> > > > So I have a list of qobjects like [qObj1, qObj2, qObj3].
>
> > > > What I want is something like Sample.objects.filter((qObj1 | qObj2),
> > > > qObj3)
>
> > > > I know that the default is for all Q objects to be "ANDed" together.
> > > > I think the join operation is not going to work here, nor is
> > > > concatenation, but is there something obvious that I'm missing?
>
> > > > THANK YOU :>
>
> > > Documentation on how to combine Q objects:
>
> > >http://docs.djangoproject.com/en/1.1/topics/db/queries/#complex-looku...
>
> > > So you want to loop through them, and 'or' them together..
>
> > > filters = [ q1, q2, q3, q4, q5 ]
> > > q = None
> > > for f in filters:
> > >  q = q | f if q else f
> > > Foo.objects.filter(q)
>
> > Refining a little:
>
> > filters = [q1,q2,q3,q4,q5]
> > q = Q()
> > for f in filters:
> >     q |= f
> > Foo.objects.filter(q)
>
> > Q() is identity for & and |.
>
> > > Tom
>
> > > --
> > > You received this message because you are subscribed to the Google Groups
> > > "Django users" group.
> > > To post to this group, send email to django-us...@googlegroups.com.
> > > To unsubscribe from this group, send email to
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> > > .
> > > For more options, visit this group at
> > >http://groups.google.com/group/django-users?hl=en.
>
> > __
> > Vinícius Mendes
> > Solucione Sistemashttp://solucione.info/

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Re: Custom QuerySet method that has an instance.save() error

[Tom M]

Ok, I definitely did this before posting, but deleting all .pyc files
in the django path (again) did fix it this time (as suggested
somewhere). How confusing is pdb to show you a .py source code file,
with no apparent problem, when the mismatch occurred in a .pyc for a
previous and different .py file?



On Apr 6, 5:53 pm, Tom M <mediaf...@googlemail.com> wrote:
> Hi,
>
> I'm trying to use Model Managers to write some per model
> functionality. I have a Book model that needs to be able to convert
> some of it's members into SoldBook items.
>
> I want to be able to do:
> Book.objects.filter(supplier='Jones').convert_sold()
>
> I'm basing my code 
> onhttp://stackoverflow.com/questions/2163151?tab=votes#tab-top
> but my model looks like this:
>
> from custom_queryset import CustomQuerySetManager #see link above
> from django.db.models.query import QuerySet
>
> class Book(models.Model):
>     objects = CustomQuerySetManager()
>
>     class QuerySet(QuerySet):
>         def convert_sold(self):
>             for book in self.all():
>                 sb = SoldBook()
>                 sb.title = book.title
>                 #etc
>                 sb.save()
>                 book.delete()
>
> but when I call it with
> Book.objects.filter(supplier='Jones').convert_sold()
>
> File "/home/user/webapps/django/lib/python2.5/django/db/models/sql/
> compiler.py", line 843, in as_sql
>     placeholder = field.get_placeholder(val, self.connection)
> TypeError: get_placeholder() takes exactly 2 arguments (3 given)
>
> Unfortunately I'm using django trunk revision 11728 (5 months old?)
> because webfaction haven't fixed their GIS database support for more
> recent djangos :-(
>
> Any idea how to fix this would be greatly appreciated.

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Custom QuerySet method that has an instance.save() error

[Tom M]

Hi,

I'm trying to use Model Managers to write some per model
functionality. I have a Book model that needs to be able to convert
some of it's members into SoldBook items.

I want to be able to do:
Book.objects.filter(supplier='Jones').convert_sold()

I'm basing my code on 
http://stackoverflow.com/questions/2163151?tab=votes#tab-top
but my model looks like this:

from custom_queryset import CustomQuerySetManager #see link above
from django.db.models.query import QuerySet

class Book(models.Model):
objects = CustomQuerySetManager()

class QuerySet(QuerySet):
def convert_sold(self):
for book in self.all():
sb = SoldBook()
sb.title = book.title
#etc
sb.save()
book.delete()

but when I call it with
Book.objects.filter(supplier='Jones').convert_sold()

File "/home/user/webapps/django/lib/python2.5/django/db/models/sql/
compiler.py", line 843, in as_sql
placeholder = field.get_placeholder(val, self.connection)
TypeError: get_placeholder() takes exactly 2 arguments (3 given)

Unfortunately I'm using django trunk revision 11728 (5 months old?)
because webfaction haven't fixed their GIS database support for more
recent djangos :-(

Any idea how to fix this would be greatly appreciated.

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