I have created a simple model - the instances of which I will be saving through the admin interface.
The field hashval needs to have the hashed value of title. It seems to just have the default hashvalue for every entry. How do I fix that ? Additionally, it should also get updated when title is updated. Any help in achieving this will be much appreciated. (Please point out if any duplicates exist)
class Entry(models.Model):
created = models.DateTimeField(auto_now_add=True)
title = models.CharField(max_length=50)
content = models.TextField()
hashval = models.BigIntegerField()
hashval = abs(hash(title))
def __unicode__(self):
return smart_unicode(self.title + " " + str(self.hashval))
class Meta:
verbose_name_plural = 'Entries'
One option is to override your save method to apply this before it's saved.
class Entry(models.Model):
created = models.DateTimeField(auto_now_add=True)
title = models.CharField(max_length=50)
content = models.TextField()
# Need to specify it as blank=True here or
# in the form so it can be ignored when the form is cleaned
hashval = models.BigIntegerField(blank=True)
def save(self, *args, **kwargs):
self.hashval = abs(hash(self.title))
return super(Entry, self).save(*args, **kwargs)
Related
I have two tables, in one of which the possible items with their properties are recorded, in the other the stock levels of these respective items are recorded.
class itemtype(models.Model):
item_id = models.IntegerField(primary_key=True)
item_name = models.CharField(max_length=100)
group_name = models.CharField(max_length=100)
category_name = models.CharField(max_length=100)
mass = models.FloatField()
volume = models.FloatField()
packaged_volume = models.FloatField(null=True)
used_in_storage = models.BooleanField(default=False, null=True)
class Meta:
indexes = [
models.Index(fields=['item_id'])
]
def __str__(self):
return '{}, {}'.format(self.item_id, self.item_name)
class material_storage(models.Model):
storage_id = models.AutoField(primary_key=True)
material = models.ForeignKey(itemtype, on_delete=models.PROTECT)
amount_total = models.IntegerField(null=True)
price_avg = models.FloatField(null=True)
amount = models.IntegerField(null=True)
price = models.FloatField(null=True)
timestamp = models.DateTimeField(default=timezone.now)
def __str__(self):
return '{}, {} avg.: {} ISK'.format(self.material, self.amount, self.price)
I have a ModelForm based on the table material_storage, in which a checkbox indicates whether transport costs should be included or not.
In the form_valid() method of this ModelForm class the calculations are performed. To do so, I have to retrieve the volume per unit of the given item to use it for my transport cost calculations. Trying to geht that value the way shown below leads to an error I don't really understand.
class MaterialChoiceField(forms.ModelChoiceField):
def label_from_instance(self, obj):
return obj.item_name
class NewAssetForm(forms.ModelForm):
material = MaterialChoiceField(models.itemtype.objects.filter(used_in_storage= True))
needs_transport = forms.BooleanField(required=False)
def __init__(self, *args, **kwargs):
super(NewAssetForm, self).__init__(*args, **kwargs)
self.fields['amount'].widget.attrs['min'] = 1
self.fields['price'].widget.attrs['min'] = 0.00
class Meta:
model = models.material_storage
fields = (
'material',
'amount',
'price',
)
widgets = {
'material': forms.Select(),
}
class NewItemView(FormView):
template_name = 'assetmanager/newasset.html'
form_class = forms.NewAssetForm
success_url = '/storage/current'
def form_valid(self, form):
unit_volume = itemtype.objects.values('packaged_volume').filter(item_id=form.cleaned_data['material'])[0]['packaged_volume']
I believe that this has something to do with querying a different model than specified in the form, but I don't understand what exactly is the problem. Especially the fact, that running the exact same query in the django shell returns the correct value does not really help to understand what is going wrong here. Could somebody please tell me how to get the desired value the correct way?
Change last line from:
unit_volume = itemtype.objects.values('packaged_volume').filter(item_id=form.cleaned_data['material'])[0]['packaged_volume']
to:
unit_volume = itemtype.objects.values('packaged_volume').filter(item_id=form.cleaned_data['material'].item_id)[0]['packaged_volume']
The error says, you are giving Item instance to the query, where is item_id asked.
I am testing forms and nesting models in django. In my Project a Person can enter departure, arrival (city names) and choose a weekly day (Mon-Fri). Maybe he drives every “Tuesday” from Amsterdam to Paris. I wanted this constellation to be unique – just for fun. So If another user enters the same route the relation should be linked to the same Car.object.
Models.py
class Person(models.Model):
name = models.CharField(max_length=255, blank=False, unique=True)
route = models.ManyToManyField('Car')
def __str__(self):
return self.name
class Car(models.Model):
name = models.CharField(max_length=255, blank=False, unique=True)
weekdays = models.ForeignKey('Week', null=True, blank=False, on_delete=models.SET_NULL)
departure = models.CharField(max_length=255, blank=False)
arrival = models.CharField(max_length=255, blank=False)
class Meta:
unique_together = ['weekdays', 'departure', 'arrival'] # --- Unique combination
def __str__(self):
return self.name
class Week(models.Model):
day = models.CharField(max_length=255, blank=False, unique=True)
def __str__(self):
return self.day
views.py
class RouteCreateView(CreateView):
model = Person
template_name ="testa/create_route.html"
form_class = RouteForm
success_url = reverse_lazy('testa:testa_home')
def form_valid(self, form):
return super().form_valid(form)
forms.py
class RouteForm(forms.ModelForm):
# --- apply ChoiceField
day = forms.ModelChoiceField(queryset=None)
car_name = forms.CharField()
departure = forms.CharField()
arrival = forms.CharField()
class Meta:
model = Person
fields = [
'name'
]
def __init__(self, *args, **kwargs):
super(RouteForm, self).__init__(*args, **kwargs)
self.fields['day'].queryset = Week.objects.all()
def save(self, commit=True):
personData = super().save(commit)
data = self.cleaned_data
carData = Car(name=data['car_name'], weekdays=data['day'], departure=data['departure'], arrival=data['arrival'])
if commit:
carData.save()
personData.route.add(carData) # --- save m2m relation
return personData
If i enter two times for example „“Tuesday” from Amsterdam to Paris “ then an Error Message appears obviously, this error message (it´s german), telling me I have a double entry / Key.
Question
So my save()Method does not work because I need some kind of logic, so that Django takes the existing car.object or creates a new - if it is not a double entry. But I do not know where to start? The easiest way would be to get some kind of response from my model meta option Car.unique_together so "if it´s an “double-key error” then take the existing object". Is there a way to fetch the response? And what kind of Values it would be, only errors, could not find any hint in the doc? Or should I try some logic with exists()
That was my kind of idea / approach of a new save() 😊
def save(self, commit=True):
personData = super().save(commit)
data = self.cleaned_data
carData = Car(name=data['car_name'], weekdays=data['day'], departure=data['departure'], arrival=data['arrival'])
if commit:
# Check if database sends unique_together response
# if yes
if Car.Meta.unique_together is True:
getAlternative = Car.object.get(Meta.unique_together) # --- get the object which already exist
personData.route.add(getAlternative) # --- save m2m relation
# if not
else:
carData.save() # --- save object
personData.route.add(carData) # --- save m2m relation
return personData
obviously i get a error message: type object 'Car' has no attribute
'Meta'
Theres get_or_create for such use case: https://docs.djangoproject.com/en/2.2/ref/models/querysets/#get-or-create
...
car, created = Car.objects.get_or_create(
weekdays=data['day'],
departure=data['departure'],
arrival=data['arrival'],
defaults = dict(name=data['car_name']),
)
personData.route.add(car)
...
Obviously given name gets ignored if another car with same weekdas, departure, arrival has been found.
I suggest to put the code for creating the car and adding the route in a transaction.atomic() https://docs.djangoproject.com/en/2.2/topics/db/transactions/#django.db.transaction.atomic
Appologies for the beginner question and/or stupidity - I'm learning as I go.... I'm trying to pass a user entered url of a PubMed article to access the metadata for that article. I'm using the following code, but I cannot access anything form the save method in he 'Entry' model. For example in my html form I can display {{entry.date_added }} in a form but not {{ entry.title}}. I suspect it's a simple answer but not obvious to me. Thanks for any help.
models.py
from django.db import models
from django.contrib.auth.models import User
import pubmed_lookup
from django.utils.html import strip_tags
class Topic(models.Model):
"""Broad topic to house articles"""
text = models.CharField(max_length=200)
date_added = models.DateTimeField(auto_now_add=True)
owner = models.ForeignKey(User, on_delete=models.CASCADE)
def __str__(self):
"""Return a string representation of the model"""
return self.text
class Entry(models.Model):
"""Enter and define article from topic"""
topic = models.ForeignKey(Topic, on_delete=models.CASCADE)
pub_med_url = models.URLField(unique=True)
date_added = models.DateTimeField(auto_now_add=True)
def save(self, *args, **kwargs):
query = self.pub_med_url
email = "david.hallsworth#hotmail.com"
lookup = pubmed_lookup.PubMedLookup(query, email)
publication = pubmed_lookup.Publication(lookup)
self.title = strip_tags(publication.title)
self.authors = publication.authors
self.first_author = publication.first_author
self.last_author = publication.last_author
self.journal = publication.journal
self.year = publication.year
self.month = publication.month
self.day = publication.day
self.url = publication.url
self.citation = publication.cite()
self.mini_citation = publication.cite_mini()
self.abstract = strip_tags(publication.abstract)
super().save(*args, **kwargs)
class Meta:
verbose_name_plural = 'articles'
def __str__(self):
return "{} - {} - {} - {} [{}]".format(self.year,
self.first_author, self.journal, self.title, str(self.pmid), )
In Django ORM, you have to manually specify all fields that need to be saved. Simply saving it as self.foo = bar in the save method is stored in the Entry instance object (=in memory), but not in the database. That is, there is no persistence. Specify all the fields that need to be saved in the model and run python manage.py makemigrations,python manage.py migrate. Assigning fields to the model is actually the task of designing the relational database.
class Entry(models.Model):
"""Enter and define article from topic"""
topic = models.ForeignKey(Topic, on_delete=models.CASCADE)
pub_med_url = models.URLField(unique=True)
date_added = models.DateTimeField(auto_now_add=True)
title = models.CharField(...)
authors = models.CharField(...)
...
def assign_some_data_from_pubmed(self):
email = "david.hallsworth#hotmail.com"
lookup = pubmed_lookup.PubMedLookup(query, email)
publication = pubmed_lookup.Publication(lookup)
self.title = strip_tags(publication.title)
self.authors = publication.authors
self.first_author = publication.first_author
self.last_author = publication.last_author
self.journal = publication.journal
self.year = publication.year
self.month = publication.month
self.day = publication.day
self.url = publication.url
self.citation = publication.cite()
self.mini_citation = publication.cite_mini()
self.abstract = strip_tags(publication.abstract)
Usage:
entry = Entry(...)
entry.assign_some_data_from_pubmed()
entry.save()
I have this models:
class Country(models.Model):
name = models.CharField(max_length=250)
def __str__(self):
return str(self.name)
class City(models.Model):
name = models.CharField(max_length=250)
country = models.ForeignKey(Country, default=None, blank=True)
def __str__(self):
return str(self.name)
class Airport(models.Model):
name = models.CharField(max_length=250)
city = models.ForeignKey(City, default=None, blank=True)
def __str__(self):
return "{0} - {1} - {2}".format(self.city, self.city.country, self.name)
class Tour(models.Model):
title = models.CharField(max_length=200)
tour_from = models.ForeignKey(Airport)
tour_to = models.ForeignKey(Airport)
def __str__(self):
return str(self.title)
For string representation of Airport Django sends many requests to DB:
302.06 ms (591 queries including 586 similar and 586 duplicates )
Queries screenshot:
At tour/create page I have a ModelForm for creating a tour and Django sends these queries for displaying form.
forms.py:
class TourCreateForm(forms.ModelForm):
class Meta:
model = Tour
fields = ['title', 'tour_from', 'tour_to']
views.py:
class DashboardTourCreate(CreateView):
model = Tour
template_name = "dashboard/tour/create.html"
form_class = TourCreateForm
def get_context_data(self, **kwargs):
context = super(DashboardTourCreate, self).get_context_data(**kwargs)
context['page_name'] = ['tour', 'tour-index']
context['page_title'] = "Create Tour"
return context
How I can reduce queries count?
Root Cause
def __str__(self):
return "{0} - {1} - {2}".format(self.city, self.city.country, self.name)
When the tour_to and tour_from fields are rendered as <option> in the <select> widget the Airport.__str__ method is called. Because Airport.__str__ has self.city.county and both of these are ForeignKey's, the Django ORM issues a query to grab the airports city and the citys country.
And it does this for every single Airport that is an <option> which means the problem will get progressively worse the more Airport's that are added.
Solution
Leverage select_related[1]. select_related will tell the Django ORM to pull in the related fields ('city', 'county') whenever it grabs an Airport.
class TourCreateForm(forms.ModelForm):
class Meta:
model = Tour
fields = ['title', 'tour_from', 'tour_to']
def __init__(self, *args, **kwargs):
super().__init__(*args, **kwargs)
self.fields['tour_from'].queryset = Airport.objects.select_related(
'city__country',
)
self.fields['tour_to'].queryset = Airport.objects.select_related(
'city__country',
)
[1] https://docs.djangoproject.com/en/2.1/ref/models/querysets/#select-related
As f-string is a string literal expressions evaluated at run time link, this might be faster that other string format but i am not fully sure. I am expecting following modification may reduce the over all time.
class Airport(models.Model):
name = models.CharField(max_length=250)
city = models.ForeignKey(City, default=None, blank=True)
def __str__(self):
return f"{self.city} - {self.city.country} - {self.name}"
I fix this issue by adding Queryset to forms.py:
class TourCreateForm(BaseForm):
airports = Airport.objects.select_related('city', 'city__country').all()
tour_from = forms.ModelChoiceField(queryset=airports)
tour_to = forms.ModelChoiceField(queryset=airports)
But I think this is not correct!
I have the following models:
class Quiver(models.Model):
user = models.ForeignKey(settings.AUTH_USER_MODEL)
is_default = models.BooleanField(default=False)
type = models.CharField(max_length=1, choices=QUIVER_TYPES)
category = models.CharField(max_length=255, choices=QUIVER_CATEGORIES)
def __unicode__(self):
return u'[%s] %s %s quiver' % (
self.user.username,
self.get_type_display(),
self.get_category_display())
class Image(models.Model):
photo = models.ImageField(upload_to=get_upload_file_path)
is_cover = models.BooleanField(default=False)
content_type = models.ForeignKey(ContentType)
object_id = models.PositiveIntegerField()
content_object = generic.GenericForeignKey()
def save(self, *args, **kwargs):
try:
this = Image.objects.get(pk=self.pk)
if this.photo != self.photo:
this.photo.delete(save=False)
except Image.DoesNotExist:
pass
super(Image, self).save(*args, **kwargs)
class Surfboard(models.Model):
quiver = models.ForeignKey(Quiver)
brand = models.CharField(max_length=255)
model = models.CharField(max_length=255)
length = models.CharField(max_length=255)
width = models.CharField(max_length=255, blank=True)
thickness = models.CharField(max_length=255, blank=True)
volume = models.CharField(max_length=255, blank=True)
images = generic.GenericRelation(Image)
def __unicode__(self):
return u'%s %s %s' % (self.length, self.brand, self.model)
def get_cover_image(self):
"Returns the cover image from the images uploaded or a default one"
for image in self.images.all():
if image.is_cover:
return image
return None
I'd like to be able to have the same form I have in the admin in my frontend view /surfboard/add:
As a new Django fan and user, I started to create the form from scratch. Not being able to do what I want with including the foreign key "quiver" as a dropdown list, I found in the doc the ModelForm, and decided to use it, so here what I got:
class SurfboardForm(ModelForm):
class Meta:
model = Surfboard
In my view, it looks like this and it's already a good start:
So now, I wanted to have a way to add pictures at the same time, and they are linked to a surfboard via a Generic Relation. Here I don't find the way to do a implementation like in the admin, and get frustrated. Any tips to do so?
Thanks!
What you seek is called an inline formset - see the docs for more.
It's also handy that you can render a formset quickly with {{ formset.as_p }}, but you'll need to write some JavaScript (or use the JavaScript that's used in the Django admin) to handle adding and removing forms.