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Python convert string to class

I want to do a query on the django User table like this:
u = User.objects.filter(member__in = member_list)
where:
class Member(models.Model):
user = models.OneToOneField(User, on_delete=models.CASCADE)
dob = models.DateField('Date of Birth', blank=True, null=True)
and member_list is a list of eligible members.
The query works fine but the problem is I do not actually know the model member is called member. It could be called anything.
I store the name of the model I want in a model called Category. I have a link to the name of the model through content_type.Category is defined as:
class Category(models.Model):
name = models.CharField('Category', max_length=30)
content_type = models.ForeignKey(ContentType)
filter_condition = JSONField(default="{}", help_text=_(u"Django ORM compatible lookup kwargs which are used to get the list of objects."))
user_link = models.CharField(_(u"Link to User table"), max_length=64, help_text=_(u"Name of the model field which links to the User table. 'No-link' means this is the User table."), default="No-link")
def clean (self):
if self.user_link == "No-link":
if self.content_type.app_label == "auth" and self.content_type.model == "user":
pass
else:
raise ValidationError(
_("Must specify the field that links to the user table.")
)
else:
if not hasattr(apps.get_model(self.content_type.app_label, self.content_type.model), self.user_link):
raise ValidationError(
_("Must specify the field that links to the user table.")
)
def __unicode__(self):
return self.name
def _get_user_filter (self):
return str(self.content_type.app_label)+'.'+str(self.content_type.model)+'.'+str(self.user_link)+'__in'
def _get_filter(self):
# simplejson likes to put unicode objects as dictionary keys
# but keyword arguments must be str type
fc = {}
for k,v in self.filter_condition.iteritems():
fc.update({str(k): v})
return fc
def object_list(self):
return self.content_type.model_class()._default_manager.filter(**self._get_filter())
def object_count(self):
return self.object_list().count()
class Meta:
verbose_name = _("Category")
verbose_name_plural = _("Categories")
ordering = ('name',)
So I can retrieve the name of the model that links to User but I then need to convert it into a class which I can include in a query.
I can create an object x = category.content_type.model_class() which gives me <class 'cltc.models.Member'> but when I them perform a query s = User.objects.filter(x = c.category.object_list()) I get the error Cannot resolve keyword 'x' into field.
Any thoughts most welcome.

The left hand side of the filter argument is a keyword, not a python object, so x is treated as 'x', and Django expects a field called x.
To get around this, you can ensure that x is a string, and then use the python **kwarg syntax:
s = User.objects.filter(**{x: c.category.object_list()})
Thanks to https://stackoverflow.com/a/4720109/823020 for this.

adding / editing django generic foreign key objects

Model Device:
class Device(models.Model):
device_code = models.CharField(max_length=64,unique=True)
is_enabled = models.BooleanField(default=False)
def __unicode__(self):
return u'%s: %s' % (self.device_code, 'ENABLED' if self.is_enabled else 'DISABLED')
Model AttributeValues:
class AttributeValue(models.Model):
attribute = models.ForeignKey(Attribute)
content_type = models.ForeignKey(ContentType)
object_id = models.PositiveIntegerField()
content_object = GenericForeignKey('content_type', 'object_id')
class Meta:
abstract = True
unique_together = (
('attribute', 'content_type','object_id'),
)
index_together = (
('content_type','object_id'),
)
#property
def formatted(self):
"""
PLEASE SELECT RELATED ATTRIBUTE BEFORE USING THIS FUNCTION
"""
return self.attribute.format % self.value
def save(self,*args,**kwargs):
if hasattr(self.content_object,'invalidate_cache') and callable(self.content_object.invalidate_cache):
self.content_object.invalidate_cache()
super(AttributeValue,self).save(*args, **kwargs)
def __unicode__(self):
return u'%s %s' % (self.attribute.name, self.value)
class NumericAttributeValue(AttributeValue):
value = models.DecimalField(max_digits=12,decimal_places=4)
class LongTextAttributeValue(AttributeValue):
value = models.TextField()
class ShortTextAttributeValue(AttributeValue):
value = models.CharField(max_length=255)
class FileAttributeValue(AttributeValue):
attribute_file = models.FileField(upload_to="attribute_imgs")
Model Attribute:
ATTRIBUTE_TYPE_CHOICES = (
('n','Numeric'),
('s','Short Text (255)'),
('m','Long Text')
)
class Attribute(models.Model):
name = models.CharField(max_length=255)
code = models.CharField(max_length=64,unique=True)
attribute_type = models.CharField(max_length=1,choices=ATTRIBUTE_TYPE_CHOICES)
sorting_order = models.PositiveIntegerField(default=0)
show = models.BooleanField(default=False)
format = models.CharField(max_length=64,default='%s')
class Meta:
ordering = ['sorting_order','name']
def __unicode__(self):
return self.name
In my device editing (adding) page, it needs to be able to create or select an attribute, then create (or edit / delete) an attribute value (could be a numeric value, long text value, short text value or a file) associated to this attribute, and the current (or new) device. How would you create a django formset for this kind of scenario?

I had to solve a similar problem and django-polymorphic worked for me.
If you define an abstract model as the parent, then it allows you to select any child models that the parent is based on in the Django admin interface (when selecting a foreign-key for example).
You will have to make some changes in your model & admin to get it working (for eg; you won't need GenericForeignKey).
https://django-polymorphic.readthedocs.org/en/latest/

How to filter records of ManyToManyField?

I have following Django models:
class TopicLabel(models.Model):
name = models.CharField(max_length=256)
order = models.IntegerField(null=True, blank=True)
topics = models.ManyToManyField(Topic, through='TopicLabelConnection')
class Topic(models.Model):
title = models.CharField(max_length=140)
visible = models.NullBooleanField(null=True, blank=True, default=False)
def __unicode__(self):
return self.title
class Meta:
verbose_name = _('topic')
verbose_name_plural = _('topics')
class TopicLabelConnection(models.Model):
topicId = models.ForeignKey(Topic, related_name='connection_topic')
labelId = models.ForeignKey(TopicLabel, related_name='connection_label')
def __unicode__(self):
return self.labelId.name + ' / ' + self.topicId.title
I want to create a method of TopicLabel, which will return to me all topics in the TopicLabel.topic collection, which have Topic.visible = True.
I want to program a Django equivalent of the following query:
SELECT *
FROM OPINIONS_TOPICLABELCONNECTION, OPINIONS_TOPIC
WHERE (OPINIONS_TOPICLABELCONNECTION.topicId_id = OPINIONS_TOPIC.id) AND
(OPINIONS_TOPICLABELCONNECTION.labelId_id = X) AND
(OPINIONS_TOPIC.visible = 1)
where X is the primary key of the topic label.
I tried following method definitions and they all failed:
1)
class TopicLabel(models.Model):
[...]
def getVisibleTopics():
return topics.filter(connection_topic__visible=True)
2)
class TopicLabel(models.Model):
[...]
def getVisibleTopics():
return topics.filter(visible=True)
3)
class TopicLabel(models.Model):
[...]
def getVisibleTopics():
return Topic.objects.filter(connection_label__visible=True).filter(connection_label__id=self.id)
4)
class TopicLabel(models.Model):
[...]
def getVisibleTopics():
return Topic.objects.filter(connection_label__visible=True).filter(connection_label__id=self.id)
5)
class TopicLabel(models.Model):
[...]
def getVisibleTopics():
return topics.filter(connection_topicId__visible=True)
What is the correct code?

First, you need to have self as the first parameter on a method. Then filter the topics. try this:
class TopicLabel(models.Model):
[...]
def getVisibleTopics(self):
return self.topics.filter(visible=True)
Also, is there a reason you are creating a custom through table? It doesn't look like you are adding any extra data to it.

how to handle django many to many mapper object [duplicate]

This question already has an answer here:
Django: show list of many to many items in the admin interface
(1 answer)
Closed 9 years ago.
i have model :
class tags(models.Model):
""" This is the tag model """
tag = models.CharField(max_length=15) # Tag name
tagDescription = models.TextField() # Tag Description
tagSlug = models.CharField(max_length=400) # Extra info can be added to the existing tag using this field
createdAt = models.DateTimeField(auto_now_add=True)
updatedAt = models.DateTimeField(auto_now=True)
def __unicode__(self):
return unicode(self.tag)
class stores(models.Model):
""" This is the store model """
storeName = models.CharField(max_length=15) # Store Name
storeDescription = models.TextField() # Store Description
storeURL = models.URLField() # Store URL
storePopularityNumber = models.IntegerField(max_length=1) # Store Popularity Number
storeImage = models.ImageField(upload_to=storeImageDir) # Store Image
storeSlug = models.CharField(max_length=400) # This is the text you see in the URL
createdAt = models.DateTimeField(auto_now_add=True) # Time at which store is created
updatedAt = models.DateTimeField(auto_now=True) # Time at which store is updated
storeTags = models.ManyToManyField(tags) # All the tags associated with the store
def __unicode__(self):
return unicode(self.storeName)
def StoreTags(self):
return unicode(self.storeTags.all())
It is displaying [] under StoreTags
this is storesAdmin class:
class storesAdmin(admin.ModelAdmin):
list_display = ('storeName','storeDescription','storeURL',
'storePopularityNumber','storeImage',
'storeSlug','createdAt','createdAt','StoreTags'
)
Why it is displaying like that i even tried to convert it into unicode but it not working..

Avoid using CamelCase in Model Fields. Django Codigo Style - Model Field
"Field names should be all lowercase, using underscores instead of camelCase."
Avoid using CamelCase in functions and methods.
"Use underscores, not camelCase, for variable, function and method names (i.e. poll.get_unique_voters(), not poll.getUniqueVoters)."
Try choosing another name for storetags method. Maybe it clashes with storetags field name.django hash object

Try with code:
models
class Tags(models.Model):
#...
def __unicode__(self):
return '%s' % self.tag
class Stores(models.Model):
#...
def __unicode__(self):
return '%s' % self.storeTags.tag
admin, list_display is not supported to ManyToMany, i'm remove storetags
class storesAdmin(admin.ModelAdmin):
list_display = ('storename','storedescription','storeurl',
'storepopularitynumber','storeimage',
'storeslug','createdat','createdat'
)
Tell me if it works correctly.

How to store functions in django models

edit: I completely rewrote the question as the original one didn't clearly explain my question
I want to run a function which is specific to each particular model instance.
Ideally I want something like this:
class MyModel(models.Model):
data = models.CharField(max_length=100)
perform_unique_action = models.FunctionField() #stores a function specific to this instance
x = MyModel(data='originalx', perform_unique_action=func_for_x)
x.perform_unique_action() #will do whatever is specified for instance x
y = MyModel(data='originaly', perform_unique_action=func_for_y)
y.perform_unique_action() #will do whatever is specified for instance y
However there is no datatype FunctionField. Normally this would be solvable with inheritance, and creating subclasses of MyModel, maybe like this:
class MyModel(models.Model):
data = models.CharField(max_length=100)
perform_unique_action = default_function
class MyModelX(MyModel):
perform_unique_action = function_X
class MyModelY(MyModel):
perform_unique_action = function_Y
x = MyModelX(data='originalx')
x.perform_unique_action() #will do whatever is specified for instance x
y = MyModelY(data='originaly')
y.perform_unique_action() #will do whatever is specified for instance y
Unfortunately, I don't think I can use inheritance because I am trying to access the function this way:
class MyModel(models.Model):
data = models.CharField(max_length=100)
perform_unique_action = default_function
class SecondModel(models.Model):
other_data = models.IntegerField()
mymodel = models.ForeignKey(MyModel)
secondmodel = SecondModel.objects.get(other_data=3)
secondmodel.mymodel.perform_unique_action()
The problem seems to be that I don't know what type the foreign key is going to be in SecondModel if I override the perform_unique_action in subclasses.
Can I access MyModel from SecondModel as a foreign key and still have a unique function for each instance of MyModel?

This works for me. I haven't tested it, but you should be able to create another class and override their methods and it'll work. Check the class Meta line, it'll treat it as an abstract class. Here's an example of my actual classes that I'm working on right now.
EDIT: Added VoteComment class and tested it. It works as expected!
class Vote(models.Model):
VOTE_ENUM = (
(VoteEnum.DOWN_VOTE, VoteEnum.toString(VoteEnum.DOWN_VOTE)),
(VoteEnum.NONE, VoteEnum.toString(VoteEnum.NONE)),
(VoteEnum.UP_VOTE, VoteEnum.toString(VoteEnum.UP_VOTE)),
)
question = models.ForeignKey(Question, null=False, editable=False, blank=False)
voter = models.ForeignKey(User, blank=False, null=False, editable=False)
vote_type = models.SmallIntegerField(default=0, null=False, blank=False, choices=VOTE_ENUM)
class Meta:
abstract = True
def is_upvote(self):
return self.vote_type > 0
def is_downvote(self):
return self.vote_type < 0
class VoteAnswer(Vote):
answer = models.ForeignKey(Answer, null=False, editable=False, blank=False)
class Meta:
unique_together = (("voter", "answer"),) # to prevent user from voting on the same question/answer/comment again
def __unicode__(self):
vote_type = "UP" if vote_type > 0 else ("DOWN" if vote_type < 0 else "NONE")
return u"{0}: [{1}] {2}".format(user.username, vote_type, answer.text[:32])
def is_upvote(self):
return "FOO! "+str(super(VoteAnswer, self).is_upvote())
class VoteComment(Vote):
comment = models.ForeignKey(Comment, null=False, editable=False, blank=False)
class Meta:
unique_together = (("voter", "comment"),) # to prevent user from voting on the same question/answer/comment again
def __unicode__(self):
vote_type = "UP" if vote_type > 0 else ("DOWN" if vote_type < 0 else "NONE")
return u"{0}: [{1}] {2}".format(user.username, vote_type, comment.text[:32])
def is_upvote(self):
return "BAR!"

I came up with two ways of having a specific function defined for each object. One was using marshal to create bytecode which can be stored in the database (not a good way), and the other was by storing a reference to the function to be run, as suggested by Randall. Here is my solution using a stored reference:
class MyModel(models.Model):
data = models.CharField(max_length=100)
action_module = models.CharField(max_length=100)
action_function = models.CharField(max_length=100)
class SecondModel(models.Model):
other_data = models.IntegerField()
mymodel = models.ForeignKey(MyModel)
secondmodel_obj = SecondModel.objects.get(other_data=3)
#The goal is to run a function specific to the instance
#of MyModel referred to in secondmodel_obj
module_name = secondmodel_obj.mymodel.action_module
func_name = secondmodel_obj.mymodel.action_function
module = __import__(module_name)
func = vars(module)[func_name]
func()
Thanks to everyone who replied, I couldn't have got to this answer if it weren't for your help.

You could achive some similar behavior overriding the save method. And providing special callbacks to your instances.
Something like:
def default_function(instance):
#do something with the model instance
class ParentModel(model.Model):
data = models.CharField()
callback_function = default_function
def save(self, *args, **kwargs):
if hasattr(self, 'callback_function'):
self.callback_function(self)
super(ParentModel, self).save(*args, **kwargs)
class ChildModel():
different_data = models.CharField()
callback_function = other_fun_specific_to_this_model
instance = ChildModel()
#Specific function to this particular instance
instance.callback_function = lambda inst: print inst.different_data
instance.save()

You can write endpoints on your server and limit their access to just your self. Then store in each model instance corresponding url. For example:
views.py
def funx_x(request):
pass
def func_y(request):
pass
models.py:
class MyModel(models.Model):
data = models.CharField(max_length=100)
perform_unique_action = models.URLField()
and then:
x = MyModel(data='originalx', perform_unique_action='http://localhost/funx_x')
requests.post(x.perform_unique_action)

i dont know whether i understand u correct or not. but you can check out this example here.
Example:
A string representing an attribute on the model. This behaves almost the same as the callable, but self in this context is the model instance. Here's a full model example:
class Person(models.Model):
name = models.CharField(max_length=50)
birthday = models.DateField()
def decade_born_in(self):
return self.birthday.strftime('%Y')[:3] + "0's"
decade_born_in.short_description = 'Birth decade'
class PersonAdmin(admin.ModelAdmin):
list_display = ('name', 'decade_born_in')