Re: Import error: Model based on another model
Daniel,
Thanx for the answer on code execution. As far as the import issue is
concerned. I'll have a look at importing specifics. I wouldn't want you to have
to dig through my code to find a syntactic typo ... :-)
Regards,
Gerard.
Daniel Roseman wrote:
> On Sep 16, 10:08 pm, Gerard Petersen <[EMAIL PROTECTED]> wrote:
>> Daniel,
>>
>> Great one! Your suggested setup works, in the front-end that is. I have
>> quite some classes subclassed from ModelAdmin (including ProductAdmin),
>> however the "form = ProductForm" line breaks my app. I've tried several
>> import statements to get the droplist to work in the admin part. This one
>> worked: "from myforms import ProductForm" however for some strange reason it
>> now breaks on Meta class for the CustomerForm:
>>
>> http://paste.pocoo.org/show/85458/
>>
>> ... completely dazzled .. Any tips?
>
> Urgh, not enough information. My only clue would be that 'from foo
> import *' is a recipe for disaster - you're importing everything in
> the module into your namespace, and that means things could be
> overwritten somewhere. Use 'from models import MyModel, MyOtherModel'
> and 'from django import forms' (then refer to forms.ModelForm etc).
>
>
>> One concept Q: Why is it that the DB query statements to 'build' the
>> BTW_CHOICES don't get executed in models.py and do get executed in the
>> myforms.py
>
> It's because the model is defined declaratively: that is, each of the
> model fields is declared as a class-level attribute, and Django uses
> some clever metaclass stuff to actually turn them into instance
> properties (way over my head, I'm afraid). So you can't put dynamic
> code there - it would only ever get executed once, when the model is
> first defined.
>
> What we've done with the form is override the __init__ method which is
> called whenever a new form is instantiated. So our query is executed
> every time, making the choices dynamic.
>
> --
> DR.
> >
--
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Re: Import error: Model based on another model
On Sep 16, 10:08 pm, Gerard Petersen <[EMAIL PROTECTED]> wrote: > Daniel, > > Great one! Your suggested setup works, in the front-end that is. I have quite > some classes subclassed from ModelAdmin (including ProductAdmin), however the > "form = ProductForm" line breaks my app. I've tried several import statements > to get the droplist to work in the admin part. This one worked: "from myforms > import ProductForm" however for some strange reason it now breaks on Meta > class for the CustomerForm: > > http://paste.pocoo.org/show/85458/ > > ... completely dazzled .. Any tips? Urgh, not enough information. My only clue would be that 'from foo import *' is a recipe for disaster - you're importing everything in the module into your namespace, and that means things could be overwritten somewhere. Use 'from models import MyModel, MyOtherModel' and 'from django import forms' (then refer to forms.ModelForm etc). > One concept Q: Why is it that the DB query statements to 'build' the > BTW_CHOICES don't get executed in models.py and do get executed in the > myforms.py It's because the model is defined declaratively: that is, each of the model fields is declared as a class-level attribute, and Django uses some clever metaclass stuff to actually turn them into instance properties (way over my head, I'm afraid). So you can't put dynamic code there - it would only ever get executed once, when the model is first defined. What we've done with the form is override the __init__ method which is called whenever a new form is instantiated. So our query is executed every time, making the choices dynamic. -- DR. --~--~-~--~~~---~--~~ 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: Import error: Model based on another model
Daniel,
Great one! Your suggested setup works, in the front-end that is. I have quite
some classes subclassed from ModelAdmin (including ProductAdmin), however the
"form = ProductForm" line breaks my app. I've tried several import statements
to get the droplist to work in the admin part. This one worked: "from myforms
import ProductForm" however for some strange reason it now breaks on Meta class
for the CustomerForm:
http://paste.pocoo.org/show/85458/
... completely dazzled .. Any tips?
One concept Q: Why is it that the DB query statements to 'build' the
BTW_CHOICES don't get executed in models.py and do get executed in the
myforms.py
Thanx again!
Regards,
Gerard.
Daniel Roseman wrote:
> On Sep 15, 9:34 pm, Gerard Petersen <[EMAIL PROTECTED]> wrote:
>> Daniel,
>>
>> I'm building an invoice system. The data relations are as follows:
>>
>> Customer -1toN-> Orders -1toN-> Products
>>
>> The products can have different tax levels which, during creation of an
>> order, get chosen by the user from a drop downlist. As shown in my first
>> email, a tax level value (e.g. 0%, 6% or 19%) gets copied to a
>> product.tax_level attribute from the metadata model. Since the value of
>> those taxes can change overtime (by law), I copy them. If I don't copy them
>> (and use relationships), adjusting the value to a new tax level would
>> 'cripple' the old orders. Note that performance or normalisation is
>> currently not a priority, code and app readability is. Then since it's a
>> copy of the tax value level to the product it does not have to be a
>> relationship, and thus a lookup will suffice.
>>
>> Hence my earlier question, how can I fill a dropdown list (BTW_CHOICES) with
>> values from a (different) model.
>>
>> # MetaData model:http://paste.pocoo.org/show/85368/
>> - The display represents the value that the user sees in the dropdown list
>> (see below). It can be compared with the __unicode_- function for objects.
>> - The value is the actual value that is copied and on form submission stored
>> in the product object
>>
>> # Product Model:http://paste.pocoo.org/show/85370/
>>
>> The way BTW_CHOICES should be filled is '(attribute, display)' taken from
>> the metadata model:
>>
>> BTW_CHOICES = (
>> ('0.0', '0%'),
>> ('6.0', '6%'),
>> ('19.0', '19%'),
>> )
>>
>> I hope this clearifies things.
>>
>> Thanx a lot for your interest and help!
>>
>> Regards,
>>
>> Gerard.
>
>
> Hmm, an interesting problem, and I wouldn't necessarily argue with
> your decision to go a bit denormalised.
>
> I would probably approach this in a slightly different way. Rather
> than worrying about the choices in the model, I would concentrate on
> the form. Just about the only thing that defining choices in the model
> field would give you would be a get_tax_level_choices() method, which
> returns the display value rather than the database value. However in
> your case this is of little use as the values are the same, with the
> addition of the % symbol - so it's not worth it.
>
> So I'd do something like this:
>
>
> DUMMY_CHOICES = ((0, 0),)
>
> class ProductForm(forms.ModelForm):
> tax_level = forms.ChoiceField(choices = DUMMY_CHOICES)
>
> class Meta:
> model = Product
>
> def __init__(self, *args, **kwargs):
> super(ProductForm, self).__init__(*args, **kwargs)
> self.fields['tax_level'].choices = [(m.value, m.display for m
> in MetaData.objects.all()]
>
> class ProductAdmin(admin.ModelAdmin)
> form = ProductForm
>
> admin.site.register(Product, ProductAdmin)
>
>
> This code registers the form in the admin, although of course you can
> also use the form on the front end if you like. (I've included the
> line referring to ChoiceField/dummy choices, as if you take the
> choices attribute out of the model field declaration you won't get a
> ChoiceField by default in the ModelForm. You could use the existing
> BTW_CHOICES tuple there if you like, but whatever values are in it
> will be overridden by the queryset in __init__.)
>
> --
> DR.
> >
--
urls = { 'fun': 'www.zonderbroodje.nl', 'tech': 'www.gp-net.nl' }
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Re: Import error: Model based on another model
On Sep 15, 9:34 pm, Gerard Petersen <[EMAIL PROTECTED]> wrote:
> Daniel,
>
> I'm building an invoice system. The data relations are as follows:
>
> Customer -1toN-> Orders -1toN-> Products
>
> The products can have different tax levels which, during creation of an
> order, get chosen by the user from a drop downlist. As shown in my first
> email, a tax level value (e.g. 0%, 6% or 19%) gets copied to a
> product.tax_level attribute from the metadata model. Since the value of those
> taxes can change overtime (by law), I copy them. If I don't copy them (and
> use relationships), adjusting the value to a new tax level would 'cripple'
> the old orders. Note that performance or normalisation is currently not a
> priority, code and app readability is. Then since it's a copy of the tax
> value level to the product it does not have to be a relationship, and thus a
> lookup will suffice.
>
> Hence my earlier question, how can I fill a dropdown list (BTW_CHOICES) with
> values from a (different) model.
>
> # MetaData model:http://paste.pocoo.org/show/85368/
> - The display represents the value that the user sees in the dropdown list
> (see below). It can be compared with the __unicode_- function for objects.
> - The value is the actual value that is copied and on form submission stored
> in the product object
>
> # Product Model:http://paste.pocoo.org/show/85370/
>
> The way BTW_CHOICES should be filled is '(attribute, display)' taken from the
> metadata model:
>
> BTW_CHOICES = (
> ('0.0', '0%'),
> ('6.0', '6%'),
> ('19.0', '19%'),
> )
>
> I hope this clearifies things.
>
> Thanx a lot for your interest and help!
>
> Regards,
>
> Gerard.
Hmm, an interesting problem, and I wouldn't necessarily argue with
your decision to go a bit denormalised.
I would probably approach this in a slightly different way. Rather
than worrying about the choices in the model, I would concentrate on
the form. Just about the only thing that defining choices in the model
field would give you would be a get_tax_level_choices() method, which
returns the display value rather than the database value. However in
your case this is of little use as the values are the same, with the
addition of the % symbol - so it's not worth it.
So I'd do something like this:
DUMMY_CHOICES = ((0, 0),)
class ProductForm(forms.ModelForm):
tax_level = forms.ChoiceField(choices = DUMMY_CHOICES)
class Meta:
model = Product
def __init__(self, *args, **kwargs):
super(ProductForm, self).__init__(*args, **kwargs)
self.fields['tax_level'].choices = [(m.value, m.display for m
in MetaData.objects.all()]
class ProductAdmin(admin.ModelAdmin)
form = ProductForm
admin.site.register(Product, ProductAdmin)
This code registers the form in the admin, although of course you can
also use the form on the front end if you like. (I've included the
line referring to ChoiceField/dummy choices, as if you take the
choices attribute out of the model field declaration you won't get a
ChoiceField by default in the ModelForm. You could use the existing
BTW_CHOICES tuple there if you like, but whatever values are in it
will be overridden by the queryset in __init__.)
--
DR.
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Re: Import error: Model based on another model
Daniel,
I'm building an invoice system. The data relations are as follows:
Customer -1toN-> Orders -1toN-> Products
The products can have different tax levels which, during creation of an order,
get chosen by the user from a drop downlist. As shown in my first email, a tax
level value (e.g. 0%, 6% or 19%) gets copied to a product.tax_level attribute
from the metadata model. Since the value of those taxes can change overtime (by
law), I copy them. If I don't copy them (and use relationships), adjusting the
value to a new tax level would 'cripple' the old orders. Note that performance
or normalisation is currently not a priority, code and app readability is. Then
since it's a copy of the tax value level to the product it does not have to be
a relationship, and thus a lookup will suffice.
Hence my earlier question, how can I fill a dropdown list (BTW_CHOICES) with
values from a (different) model.
# MetaData model: http://paste.pocoo.org/show/85368/
- The display represents the value that the user sees in the dropdown list (see
below). It can be compared with the __unicode_- function for objects.
- The value is the actual value that is copied and on form submission stored in
the product object
# Product Model: http://paste.pocoo.org/show/85370/
The way BTW_CHOICES should be filled is '(attribute, display)' taken from the
metadata model:
BTW_CHOICES = (
('0.0', '0%'),
('6.0', '6%'),
('19.0', '19%'),
)
I hope this clearifies things.
Thanx a lot for your interest and help!
Regards,
Gerard.
Daniel Roseman wrote:
> On Sep 13, 10:56 am, Gerard Petersen <[EMAIL PROTECTED]> wrote:
>> Daniel,
>>
>>> If you want a field that's populated with values from another model,
>>> you should use a ForeignKey.
>> Is it then still possible to use filters and such, and keep it in the model
>> logic?
>>
>> Because the Meta model has these fields: 'attribute', 'value', 'display',
>> 'description'
>>
>> And it's more like a lookup then a real relation between the models Order
>> and Meta.
>
>
> I can't really understand what you're asking here, I'm afraid. Maybe
> you could post your models code (preferably on dpaste.com) along with
> some indication of what you're trying to do.
> --
> DR.
>
> >
--
urls = { 'fun': 'www.zonderbroodje.nl', 'tech': 'www.gp-net.nl' }
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Re: Import error: Model based on another model
On Sep 13, 10:56 am, Gerard Petersen <[EMAIL PROTECTED]> wrote: > Daniel, > > > If you want a field that's populated with values from another model, > > you should use a ForeignKey. > > Is it then still possible to use filters and such, and keep it in the model > logic? > > Because the Meta model has these fields: 'attribute', 'value', 'display', > 'description' > > And it's more like a lookup then a real relation between the models Order and > Meta. I can't really understand what you're asking here, I'm afraid. Maybe you could post your models code (preferably on dpaste.com) along with some indication of what you're trying to do. -- DR. --~--~-~--~~~---~--~~ 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: Import error: Model based on another model
Gerard Petersen wrote: > Daniel, > >> If you want a field that's populated with values from another model, >> you should use a ForeignKey. > Is it then still possible to use filters and such, and keep it in the model > logic? > > Because the Meta model has these fields: 'attribute', 'value', 'display', > 'description' > > And it's more like a lookup then a real relation between the models Order and > Meta. > >> Also, it's not a good idea to use Meta as the name of a model - that's >> bound to get confused with the inner Meta class which defines model >> meta-attributes like ordering. > Thanx for the tip. I already saw this one coming ... ;-) I would like to ask a similar but slightly more specific question. An Oracle database I use keeps lookup data in a Lookups table with three columns, to avoid many small tables (I assume). A Django model would be something like (untested pseudo-code): class Types(model.model): lktName = models.CharField(max_length=50) class Lookups(models.Model): lkpType = models.ForeignKey(Types) lkpValue = models.CharField(max_length=50) So I'd like to be able to populate drop-downs with (id, lkpValue) pairs for a given value of lkpType. The related tables might use a ForeignKey, but I certainly don't want to see all Lookups in a selection, just those of the relevant type. regards Steve -- Steve Holden+1 571 484 6266 +1 800 494 3119 Holden Web LLC http://www.holdenweb.com/ --~--~-~--~~~---~--~~ 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: Import error: Model based on another model
Daniel,
> If you want a field that's populated with values from another model,
> you should use a ForeignKey.
Is it then still possible to use filters and such, and keep it in the model
logic?
Because the Meta model has these fields: 'attribute', 'value', 'display',
'description'
And it's more like a lookup then a real relation between the models Order and
Meta.
> Also, it's not a good idea to use Meta as the name of a model - that's
> bound to get confused with the inner Meta class which defines model
> meta-attributes like ordering.
Thanx for the tip. I already saw this one coming ... ;-)
Regards,
Gerard.
>
> --
> DR.
> >
--
urls = { 'fun': 'www.zonderbroodje.nl', 'tech': 'www.gp-net.nl' }
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Re: Import error: Model based on another model
On Sep 13, 9:25 am, Gerard Petersen <[EMAIL PROTECTED]> wrote:
> Hi All,
>
> I need to create a field with a choice set that looks like this:
>
> BTW_CHOICES = (
> ('0.0', '0%'),
> ('6.0', '6%'),
> ('19.0', '19%'),
> )
>
> This works as expected when using dropdown lists in a form. But it needs to
> be build from data in another model. When needed in a view I can retrieve the
> raw data like this:
>
> btwchoices = Meta.objects.values_list('value',
> 'display').filter(attribute__startswith='BTW')
>
> When I put a similar line in the model class Meta is unknown. And doing a
> 'from models import...' seems very weird when I'm IN the models module. when
> I move it to a myfunctions.py I get import errors.
>
> from models import Meta
> ImportError: cannot import name Meta
>
> Can anybody give me some insights on how, and more importantly where, to
> dynamically fill this BTW_CHOICES thingy.
>
> Thanx!
>
> Regards,
>
> Gerard.
If you want a field that's populated with values from another model,
you should use a ForeignKey.
Also, it's not a good idea to use Meta as the name of a model - that's
bound to get confused with the inner Meta class which defines model
meta-attributes like ordering.
--
DR.
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Import error: Model based on another model
Hi All,
I need to create a field with a choice set that looks like this:
BTW_CHOICES = (
('0.0', '0%'),
('6.0', '6%'),
('19.0', '19%'),
)
This works as expected when using dropdown lists in a form. But it needs to be
build from data in another model. When needed in a view I can retrieve the raw
data like this:
btwchoices = Meta.objects.values_list('value',
'display').filter(attribute__startswith='BTW')
When I put a similar line in the model class Meta is unknown. And doing a 'from
models import...' seems very weird when I'm IN the models module. when I move
it to a myfunctions.py I get import errors.
from models import Meta
ImportError: cannot import name Meta
Can anybody give me some insights on how, and more importantly where, to
dynamically fill this BTW_CHOICES thingy.
Thanx!
Regards,
Gerard.
--
urls = { 'fun': 'www.zonderbroodje.nl', 'tech': 'www.gp-net.nl' }
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