Develop Reference

How to query a specific field in a model that has the same name as another field of another model

I'm trying to render the device that has the same name as the Gateway in the query so I created three models (The plant model has nothing to do with this issue so skip it ) as you can see in the models.py :
from django.db import models
infos_type= (
('ONGRID','ONGRID'),
('PV','PV'),
('HYBRID','HYBRID'),
)
infos_status= (
('etude','Etude'),
('online','Online'),
('Other','Other'),
)
infos_Device= (
('Rs485','Rs485'),
('lora','lora'),
('Other','Other'),
)
class new_Plant(models.Model):
name=models.CharField(max_length=20)
adress=models.CharField(max_length=50)
type=models.CharField(max_length=20,choices=infos_type)
location=models.CharField(max_length=50)
list_gateway=models.CharField(max_length=50)
status=models.CharField(max_length=50,choices=infos_status)
def __str__(self):
return self.name
#class Meta:
#db_table="website"
class new_Gateway(models.Model):
gatewayname=models.CharField(max_length=20)
slavename=models.CharField(max_length=20)
list_devices=models.CharField(max_length=20)
def __str__(self):
return self.gatewayname
class new_Device(models.Model):
Gateway_Name=models.CharField(max_length=20)
DeviceName=models.CharField(max_length=20)
slavename=models.CharField(max_length=20)
adress=models.CharField(max_length=20)
baud_rate=models.CharField(max_length=20)
connection_type=models.CharField(max_length=20,choices=infos_Device)
def __str__(self):
return self.DeviceName
# Create your models here.
Now as I said I want to render in a specific page , the device that Has "Gateway_Name" field same as the Gateway "gatewayname" field.
in my views.py this is what I tried but it doesn't work :
def gatewaysdevice(request,id):
gateway=new_Gateway.objects.get(id=id)
result=new_Device.objects.filter(Gateway_Name__contains=new_Gateway(gatewayname))
return render(request, 'website/gatewaysdevice.html',{'result':result})

You can try this query in your code:
result=new_Device.objects.filter(Gateway_Name__contains=gateway.gatewayname)
#If you encounter any type(object) error then use str(gateway.gatewayname).
Note : You can go with '__icontains' in above query which ignores lower and uppercase entries in Gateway_Name field for better approach.

How can I override a DjangoModelFormMutation field type in graphene?

I'm building a simple recipe storage application that uses the Graphene package for GraphQL. I've been able to use Django Forms so far very easily in my mutations, however one of my models fields is really an Enum and I'd like to expose it in Graphene/GraphQL as such.
My enum:
class Unit(Enum):
# Volume
TEASPOON = "teaspoon"
TABLESPOON = "tablespoon"
FLUID_OUNCE = "fl oz"
CUP = "cup"
US_PINT = "us pint"
IMPERIAL_PINT = "imperial pint"
US_QUART = "us quart"
IMPERIAL_QUART = "imperial quart"
US_GALLON = "us gallon"
IMPERIAL_GALLON = "imperial gallon"
MILLILITER = "milliliter"
LITER = "liter"
# Mass and Weight
POUND = "pound"
OUNCE = "ounce"
MILLIGRAM = "milligram"
GRAM = "gram"
KILOGRAM = "kilogram"
My Model:
class RecipeIngredient(TimeStampedModel):
recipe = models.ForeignKey(Recipe, on_delete=models.CASCADE, related_name='ingredients')
direction = models.ForeignKey(RecipeDirection, on_delete=models.CASCADE, null=True, related_name='ingredients')
quantity = models.DecimalField(decimal_places=2, max_digits=10)
unit = models.TextField(choices=Unit.as_tuple_list())
My form:
class RecipeIngredientForm(forms.ModelForm):
class Meta:
model = RecipeIngredient
fields = (
'recipe',
'direction',
'quantity',
'unit',
)
My Mutation:
class CreateRecipeIngredientMutation(DjangoModelFormMutation):
class Meta:
form_class = RecipeIngredientForm
exclude_fields = ('id',)
I've created this graphene enum UnitEnum = Enum.from_enum(Unit) however I haven't been able to get graphene to pick it up. I've tried adding it to the CreateRecipeIngredientMutation as a regular field like unit = UnitEnum() as well as an Input class on that mutation. So far, the closest I've gotten is this Github issue from awhile ago. After playing around with the class in an iPython shell, I think I could just do CreateRecipeIngredientMutation.Input.unit.type.of_type = UnitEnum() but this feels awful.

I came up with a solution that works but is not pretty. I used the https://github.com/hzdg/django-enumfields package to help with this.
I created my own form field:
class EnumChoiceField(enumfields.forms.EnumChoiceField):
def __init__(self, enum, *, coerce=lambda val: val, empty_value='', **kwargs):
if isinstance(enum, six.string_types):
self.enum = import_string(enum)
else:
self.enum = enum
super().__init__(coerce=coerce, empty_value=empty_value, **kwargs)
And used it in my Django form. Then in my custom AppConfig I did this:
class CoreAppConfig(AppConfig):
name = 'myapp.core'
def ready(self):
registry = get_global_registry()
#convert_form_field.register(EnumChoiceField)
def convert_form_field_to_enum(field: EnumChoiceField):
converted = registry.get_converted_field(field.enum)
if converted is None:
raise ImproperlyConfigured("Enum %r is not registered." % field.enum)
return converted(description=field.help_text, required=field.required)
And finally in my schema:
UnitEnum = Enum.from_enum(Unit)
get_global_registry().register_converted_field(Unit, UnitEnum)
I really don't like this, but couldn't think of a better way to handle this. I came across this idea when searching down another graphene django issue here https://github.com/graphql-python/graphene-django/issues/481#issuecomment-412227036.
I feel like there has to be a better way to do this.

Override imported class variables - django/python

I need to override variables (or pass dynamic data) to imported class.
filters.py
import django_filters
from .models import Gate, Tram, OperationArea, Bogie
from distutils.util import strtobool
from django import forms
class GateFilter(django_filters.FilterSet):
# Prepare dynamic lists with choices
tram_list = [(id, number) for id, number in Tram.objects.all().values_list('id', 'number')]
bogie_list = [(id, number) for id, number in Bogie.objects.all().values_list('id', 'number')]
area_list = [(id, area) for id, area in OperationArea.objects.all().values_list('id', 'area')]
# Generate fields
tram = django_filters.MultipleChoiceFilter(choices=tram_list, label=u'Tramwaj')
car = django_filters.MultipleChoiceFilter(choices=Gate.CAR_SYMBOLS, label=u'Człon')
bogie = django_filters.MultipleChoiceFilter(choices=bogie_list, label=u'Wózek')
bogie_type = django_filters.MultipleChoiceFilter(choices=Gate.BOGIE_TYPES, label=u'Typ wózka')
area = django_filters.MultipleChoiceFilter(choices=area_list, label=u'Obszar')
operation_no = django_filters.CharFilter(label=u'Numer operacji', widget=forms.TextInput(attrs={'size': '16px'}))
status = django_filters.MultipleChoiceFilter(choices=Gate.GATE_STATUSES, label=u'Status')
rating = django_filters.MultipleChoiceFilter(choices=Gate.GATE_GRADES, label=u'Ocena')
class Meta:
pass
views.py
from .filters import GateFilter
class GateListView(generic.ListView):
queryset = None
gate_type = None
template_name = 'qapp/gate/list.html'
context_object_name = 'gate_list'
paginate_by = 20
def get_queryset(self):
# Type is stored in database as big-letter word, so 'bjc' != 'BJC'.
if self.gate_type.upper() == 'BJW':
ordering = ['bogie', 'bogie_type']
else:
ordering = ['tram', 'car']
queryset = Gate.objects.filter(type=self.gate_type.upper()).order_by(*ordering)
self.gate_list = GateFilter(self.request.GET, queryset=queryset)
return self.gate_list.qs.distinct()
def get_context_data(self, **kwargs):
context = super(GateListView, self).get_context_data(**kwargs)
# Return Gate.type to template.
context['gate_type'] = self.gate_type
# Return object (for generating form) to template.
context['gate_list_filter'] = self.gate_list
return context
As you can see, in the filters.py, the data for variables tram_list, bogie_list and area_list are dynamic (fetched from database).
But during importing this class to views.py, this data becomes static.
I tried to override this values:
using #classmethod decorator in class GateFilter, and calling it
before setting self.gate_list object,
in views.py using GateFilter.tram_list (and the rest) notation,
No luck.
I can't use reload() function, due to import type (from .filters import GateFilter).
Currently for update lists in filters.py I need to rerun whole app.
This is unacceptable for business logic of my app.

This is the wrong approach. Rather, you should be using the filters that are aware of querysets and that evaluate them when required: ModelChoiceFilter and ModelMultipleChoiceFilter.
class GateFilter(django_filters.FilterSet):
team = django_filters.ModelMultipleChoiceFilter(queryset=Tram.objects.all())

django related field exists after delete

I've an Order model and others models which related with it. An user can delete any of this items and I must perform a check if the order is empty after deletion and set as active False in case true. Some basic code to ilustrate it
class Order(models.Model):
paid = models.BooleanField(default=False)
active = models.BooleanField(default=True)
user = models.ForeignKey(settings.AUTH_USER_MODEL)
def empty_order():
"""
I must implement it
"""
class HomeOrder(models.Model):
...
order = models.OneToOneField(Order, related_name='primary_home')
class TourOrder(models.Model):
...
order = models.ForeignKey(Order, related_name='tours')
I have a post_delete signals that are connected with every of this Models related to Order:
post_delete.connect(delete_order_if_empty, sender=HomeOrder)
post_delete.connect(delete_order_if_empty, sender=TourOrder)
def delete_order_if_empty(sender, instance, **kwargs):
if instance.order.empty_order():
instance.order.active = False
instance.order.save()
An Order can have one Home, so if the Home exists I can do order.primary_home, if Home does not exist it will raise an AttributeError because it is an OneToOne relationship.
An Order can have many Tours, so in the empty_order method I thought to do some checks as following.
def empty_order():
home = hasattr(self, 'primary_home') # Avoid AttributeError exception
tours = self.tours.exists()
this_order_has_something = primary_home or tours
return not this_order_has_something
Now, when I delete an HomeOrder the signal is raised but the empty_method never realized that this HomeOrder does not exists any more. Example:
>>>o=Order.objects.create(...)
>>>o.primary_home # raise AttributeError
>>>h=HomeOrder.objetcs.create(order=o, ...)
>>>o.primary_home # <HomeOrder: home-xx>
>>>h.delete()
>>>o.primary_home # still <HomeOrder: home-xx> Why?
>>>o.refresh_from_db()
>>>o.primary_home # again <HomeOrder: home-xx>

Django Integrated Test Passing When it Should Fail

I'm in the process of creating an assessment system using Django; however, I have an integrated test that passes and I'm not sure as to why (it should be failing). In the test, I set the grade field of the bobenrollment object to "Excellent". As you can see from the models below, the Enrollment model doesn't have a grade field (none of the models do). I was under the impression that dot notation of model objects would access the model fields (I'm probably incorrect about this). I don't want to write ineffective tests, so I would like to know what makes this test pass and what I should do to make it break. Thanks!
class ClassAndSemesterModelTest(TestCase):
def add_two_classes_to_semester_add_two_students_to_class(self):
first_semester = Semester.objects.create(text='201530')
edClass = EdClasses.objects.create(name='EG 5000')
edClass2 = EdClasses.objects.create(name='EG 6000')
first_semester.classes.add(edClass)
first_semester.classes.add(edClass2)
bob = Student.objects.create(name="Bob DaBuilder")
jane = Student.objects.create(name="Jane Doe")
bobenrollment = Enrollment.objects.create(student=bob, edclass=edClass)
janeenrollment = Enrollment.objects.create(student=jane,edclass=edClass)
bobenrollment2 = Enrollment.objects.create(student=bob,edclass=edClass2)
janeenrollment2 = Enrollment.objects.create(student=jane,edclass=edClass2)
def test_students_link_to_enrollments(self):
self.add_two_classes_to_semester_add_two_students_to_class()
edclass1 = EdClasses.objects.get(name="EG 5000")
bob = Student.objects.get(name="Bob DaBuilder")
#The three lines below are the subject of my question
bobenrollment = Enrollment.objects.get(edclass=edclass1, student=bob)
bobenrollment.grade = "Excellent"
self.assertEqual(bobenrollment.grade, "Excellent")
And the models below:
from django.db import models
class Student(models.Model):
name = models.TextField(default="")
def __str__(self):
return self.name
#TODO add models
class EdClasses(models.Model):
name = models.TextField(default='')
students = models.ManyToManyField(Student, through="Enrollment")
def __str__(self):
return self.name
class Semester(models.Model):
text = models.TextField(default='201530')
classes = models.ManyToManyField(EdClasses)
def __str__(self):
return self.text
class Enrollment(models.Model):
student = models.ForeignKey(Student)
edclass = models.ForeignKey(EdClasses)
Requirements.txt
beautifulsoup4==4.4.1
Django==1.5.4
ipython==3.1.0
LiveWires==2.0
nose==1.3.3
Pillow==2.7.0
projectname==0.1
pyperclip==1.5.11
pytz==2015.2
requests==2.10.0
selenium==2.53.6
six==1.9.0
South==1.0.2
swampy==2.1.7
virtualenv==1.11.5

I was under the impression that dot notation of model objects would access the model fields (I'm probably incorrect about this)
You're correct about this. What you're not taking into account is the fact that you can dynamically add properties to python objects. For instance:
In [1]: class MyClass():
...: pass
...:
In [2]: a = MyClass()
In [3]: a.im_a_property = 'hello'
In [4]: print a.im_a_property
hello
As you can see, the a instance will have the im_a_propery property even though it's not defined by the class. The same applies for the following line in your code:
bobenrollment.grade = "Excellent"
Django models override this behavior so you can seamlessly get DB values as properties of your model instance, but the instance is just a regular python object.
If you want to test the grade property gets saved correctly, you should modify your test to add the value of grade when creating the record and making sure the instance you assert against is the one you read from your DB (i.e. not modifying it beforehand).