Question

I have the following issue with Django:

My model is defined as follows:

from django.db import models

class SettingSection(models.Model):
    section = models.CharField(max_length=20)
    def __unicode__(self):
        return self.section

class SettingParam(models.Model):
    section = models.ForeignKey(SettingSection)
    param = models.CharField(max_length=20, unique=True)
    description = models.CharField(max_length=200, blank=True)
    def __unicode__(self):
        return self.param

class SettingPreset(models.Model):
    preset = models.CharField(max_length=20, unique=True)
    current = models.BooleanField()
    def __unicode__(self):
        return self.preset

class SettingValue(models.Model):
    preset = models.ForeignKey(SettingPreset)
    param = models.ForeignKey(SettingParam)
    value = models.CharField(max_length=100, blank=True)
    def __unicode__(self):
        return self.value

I have following error when trying to access any attribute of my SettingValue object:

>>> from settings.models import *
>>> preset = SettingPreset.objects.get(current=True)
>>> for section in SettingSection.objects.all():
...     for param in section.settingparam_set.all():
...             v = SettingValue.objects.filter(preset=preset, param=param)
...             print v.id, v.value
... 
Traceback (most recent call last):
  File "<console>", line 4, in <module>
AttributeError: 'QuerySet' object has no attribute 'id'

However, the attributes (“id” and “value”) seem to exist:

>>> for section in SettingSection.objects.all():
...     for param in section.settingparam_set.all():
...             v = SettingValue.objects.filter(preset=preset, param=param)
...             print v.values()
... 
[{'value': u'192.168.1.29', 'id': 1, 'preset_id': 1, 'param_id': 1}]
[{'value': u'en1', 'id': 2, 'preset_id': 1, 'param_id': 2}]
[{'value': u'0', 'id': 3, 'preset_id': 1, 'param_id': 3}]
[{'value': u'', 'id': 4, 'preset_id': 1, 'param_id': 4}]
[{'value': u'', 'id': 5, 'preset_id': 1, 'param_id': 5}]

In addition, I’m able to access any of the attributes without applying filters to my object:

>>> for v in SettingValue.objects.all():
...     print v.id, v.value
... 
1 192.168.1.29
2 en1
3 0
4 
5 

Answer 1

The variable v is a queryset, and you cannot access your models attributes via the queryset. Therefore you should try this to access the first element in your queryset:

for param in section.settingparam_set.all():
    v = SettingValue.objects.filter(preset=preset, param=param)
    print v[0].id, v[0].value #access first element in query set

Or do this to loop over the items in your queryset:

for param in section.settingparam_set.all():
    v = SettingValue.objects.filter(preset=preset, param=param)
    for item in v:
        print item.id, item.value