I'm using both django-taggit and django-filter in my web application, which stores legal decisions. My main view (below) inherits from the stock django-filter FilterView and allows people to filter the decisions by both statutes and parts of statutes.
class DecisionListView(FilterView):
context_object_name = "decision_list"
filterset_class = DecisionFilter
queryset = Decision.objects.select_related().all()
def get_context_data(self, **kwargs):
# Call the base implementation to get a context
context = super(DecisionListView, self).get_context_data(**kwargs)
# Add in querysets for all the statutes
context['statutes'] = Statute.objects.select_related().all()
context['tags'] = Decision.tags.most_common().distinct()
return context
I also tag decisions by topic when they're added and I'd like people to be able to filter on that too. I currently have the following in models.py:
class Decision(models.Model):
citation = models.CharField(max_length = 100)
decision_making_body = models.ForeignKey(DecisionMakingBody)
statute = models.ForeignKey(Statute)
paragraph = models.ForeignKey(Paragraph)
...
tags = TaggableManager()
class DecisionFilter(django_filters.FilterSet):
class Meta:
model = Decision
fields = ['statute', 'paragraph']
I tried adding 'tags' to the fields list in DecisionFilter but that had no effect, presumably because a TaggableManager is a Manager rather than a field in the database. I haven't found anything in the docs for either app that covers this. Is it possible to filter on taggit tags?
You should be able to use 'tags__name' as the search/filter field. Check out the Filtering section on http://django-taggit.readthedocs.org/en/latest/api.html#filtering
Related
Updated
I changed my simplified question into a real example.
I've created a working post response of data from the model using ModelSerialzer, which I call from a post method in a view class. I would like to add additional data to the response. This is the pertinent code from my CBV:
def post(self, request, format=None):
user_profile = UserProfiles.objects.get(user=request.user.id)
service_id = user_profile.service_id
rec_filter = Recommendations.objects.values_list('resource')
if service_id > 0:
service_name = Services.objects.get(pk=service_id)
programs = Programs.objects.filter(services=service_id)
resources_filtered = Resources.objects.filter(program__in=programs).exclude(id__in=rec_filter)
else:
service_name = 'All Services'
resources_filtered = Resources.objects.exclude(id__in=rec_filter)
serializer = ResourceSerializer(resources_filtered, many=True)
#serializer.data["service"] = service_name
return Response(serializer.data)
The commented out line was my attempt to add data base on a similar post here. I get a 500 response in my API call. What is the correct way to do it? The response data is JSON if that's necessary to mention.
This is the ModelSerializer:
class ResourceSerializer(serializers.ModelSerializer):
organization = OrganizationSerializer(read_only=True)
program = ProgramSerializer(read_only=True)
class Meta:
model = Resources
fields = [
'organization',
'program',
'link',
'contact',
'general_contact',
'eligibility',
'service_detail'
]
Test of the answer
Heres the updated code based on the answer with a correction to fix and error:
class ResourceSerializer(serializers.ModelSerializer):
organization = OrganizationSerializer(read_only=True)
program = ProgramSerializer(read_only=True)
service = serializers.SerializerMethodField()
def get_service(self, obj):
return "All Services"
class Meta:
model = Resources
fields = [
'organization',
'program',
'link',
'contact',
'general_contact',
'eligibility',
'service_detail',
'service'
]
The problem with this approach is that the value "All Services" is repeated in every row serialized. It's only needed once. I'd also like to keep the data transmitted minimized.
The problem with the original attempt is that serializer.data is immutable. It's necessary to make a copy and add to it.
serializer = ResourceSerializer(resources_filtered, many=True)
augmented_serializer_data = list(serializer.data)
augmented_serializer_data.append({'service': 'All Services'})
return Response(augmented_serializer_data)
This answer is based on one given by #andre-machado in this question.
This code here is an example to coincide with the other answer given.
You can do it in serializer itself. Define the new field required and add it in fields. Mark all the fields in serializer from resource model.
class ResourceSerializer(serializers.ModelSerializer):
service = serializers.SerializerMethodField()
def get_service(self):
return "All Services"
class Meta :
model = Resources
fields = ('service') #Mark all the fields required here from resource model
You can do it from the serilaizer. In this case i was adding the field isOpen to the response and this is how i did it .timeDifference is the name of the function that was to generate data for the extra field . I hope it helps
class ShopSearchSerializer(serializers.ModelSerializer):
isOpen = serializers.SerializerMethodField('timeDifference')
def timeDifference(self,*args):
requestTime = datetime.now()
return requestTime
class Meta:
model = Shop
fields =['name','city','street','house','opening_time','closing_time','isOpen']
I have two models in consideration. RV_Offers and RV_Details. Each offer can have multiple details i.e. I have a foreignkey relationship field in RV_Details table.
Here is my view:
rv_offers_queryset = RV_Offers.objects.all().select_related('vendor').prefetch_related('details')
details_queryset = RV_Details.objects.all().select_related('rv_offer')
title = Subquery(details_queryset.filter(
rv_offer=OuterRef("id"),
).order_by("-created_at").values("original_title")[:1])
offers_queryset = rv_offers_queryset.annotate(
title=title).filter(django_query)
offers = RVOffersSerializer(offers_queryset, many=True).data
return Response({'result': offers}, status=HTTP_200_OK)
As can be seen, I am passing the offers queryset to the serializer.
Now, here is my serializer:
class RVOffersSerializer(serializers.ModelSerializer):
details = serializers.SerializerMethodField()
vendor = VendorSerializer()
def get_details(self, obj):
queryset = RV_Details.objects.all().select_related('rv_offer')
queryset = queryset.filter(rv_offer=obj.id).latest('created_at')
return RVDetailsSerializer(queryset).data
class Meta:
model = RV_Offers
fields = '__all__'
If you look at the get_details method, I am trying to fetch the latest detail that belongs to an offer. My problem is, even though I am using select_related to optimize the query, the results are still extremely slow, In fact, I am using django debug toolbar to inspect the query and apparently select_related seems to have no effect.
What am I doing wrong or how else can I approach this problem?
This is what I did to reduce the number of queries being hit on the db:
def get_details(self, obj):
details = obj.details.last()
return RVDetailsSerializer(details).data
I was able to reduce the number of queries from 45 to 4 using this.
This is because in the view, I had already used select_related to make the queryset, which in turn is being used here using obj.
In the following model...
class Question(models.Model):
question_text = models.CharField(max_length=200)
likes = models.IntegerField(default=0)
dislikes = models.IntegerField(default=0)
pub_at = models.DateTimeField(auto_now_add=True)
category = models.ForeignKey(
Category, on_delete=models.SET_NULL, null=True)
def __str__(self):
return f"{self.question_text}"
def validity(self):
total_likes = self.likes + self.dislikes
if total_likes != 0:
return (self.likes / total_likes) * 100
else:
return 100
I want to be able to access Question.objects.get(pk=1).validity() assuming that pk=1 exists in this case. In python shell I can do this easily. But how do I do this using React. I am able to get all my questions and the fields in React without a problem but I don't think I have a way to access the validity method I created.
In this case I would suggest the following. First, remove the property from the model:
# models.py
class Question(models.Model):
question_text = models.CharField(max_length=200)
likes = models.IntegerField(default=0)
dislikes = models.IntegerField(default=0)
pub_at = models.DateTimeField(auto_now_add=True)
category = models.ForeignKey(
Category, on_delete=models.SET_NULL, null=True)
def __str__(self):
return f"{self.question_text}"
Then add a SerializerMethodField (docs) to your serializer. It is read-only and can be used to pass computed values to your views:
# serializers.py
class QuestionSerializer(serializers.ModelSerializer):
validity = serializers.SerializerMethodField()
class Meta:
model = Question
fields = ['question_text', 'likes', 'dislikes', 'pub_at', 'category', 'validity']
def get_validity(self, instance):
total_likes = instance.likes + instance.dislikes
# Your approach is not wrong. This is a more explicit way of dealing with that particular error type
try:
return (instance.likes / total_likes) * 100
except ZeroDivisionError:
return 100
Bear in mind that the Foreign Key category will be serialized as its database unique id value (Primary Key) in this case.
You might want to use the #property decorator so that you can access the value the same way you would access any of the other fields on your Question model:
class Question(models.Model):
question_text = models.CharField(max_length=200)
likes = models.IntegerField(default=0)
dislikes = models.IntegerField(default=0)
pub_at = models.DateTimeField(auto_now_add=True)
category = models.ForeignKey(
Category, on_delete=models.SET_NULL, null=True)
def __str__(self):
return f"{self.question_text}"
#property
def validity(self):
total_likes = self.likes + self.dislikes
percentage = (self.likes / total_likes) * 100
return percentage
Explanations can be found in the docs or here. Keep in mind that it will not be saved like the other attributes as columns on the database when you run migrations.
I am answering my own question here I found a solution to. Although, #property does work when rendering using a simple Django template when using React and rendering json responses validity is still not available.
In my serializers.py file I did the following...
class QuestionSerializer(serializers.ModelSerializer):
validity = serializers.ReadOnlyField()
class Meta:
model = Question
fields = '__all__'
Take away the #property from the models as it is no longer needed. This has worked for me and you can go to the Django rest_framework or test it in your React application to see if you have access to this.
I would like to know if there are any issues doing this and/or a better way. I was also trying to do validity = serializers.Field() instead of validity = serializers.ReadOnlyField() but got an error saying I needed a Field.to_representation() that takes in self, value as positional arguments.
What arguments exactly do I pass in here. I tried self, Question.validity and did not work. I am not sure what I am doing here.
As an update the method in the model I updated to...
def validity(self):
total_likes = self.likes + self.dislikes
if total_likes != 0:
return (self.likes / total_likes) * 100
else:
return 100
I did not notice before and does not really matter for the question but division by zero is not allowed being that by default division by zero will always occur.
I have a Django app, where each user can add a product with multiple possible metrics (width, height and length combination). A user must also specify in which city this product is located.
Users can also search within the database all products matching specific metrics.
I use Django 1.11 and am seaching for a solution to display on an interactive map all the products matching a queryset.
I am trying to do it with django-leaflet and django-geojson (as my db is not gis-oriented and I don't need heavy geo-computations), but I am facing some difficulties because my "PointField" is not in my product Model but in the Location Model and on the map I need to display Product properties, so I must serialize all these data together.
If you prefer code rather than words, here is a simplified version of my relevant files.
#models.py
class Product(models.Model):
name = models.CharField()
owner = models.ForeignKey(User)
photo = models.ImageField(...)
dimensions = models.ManyToManyField(Metrics)
location = models.ForeignKey(Location, related_name='products', related_query_name='product')
class Metrics(models.Model):
width = models.PositiveIntegerField()
height = models.PositiveIntegerField()
length = models.PositiveIntegerField()
class Location(models.Model):
zip_code = models.PositiveIntegerField()
city_name = models.CharField()
slug = models.SlugField(max_length=500, blank=True)
geom = PointField(default={'type': 'Point', 'coordinates': [0, 0]})
#views.py
class SearchResultListView(ListView):
model = models.Product
template_name='my_app/searchresult_list.html'
context_object_name = 'product_list'
def get_context_data(self, **kwargs):
context = super().get_context_data(**kwargs)
query_width = self.request.GET['width']
query_height = self.request.GET['height']
query_length = self.request.GET['length']
context['product_list'] = context['product_list'].filter(metrics__width=query_width,
metrics__length=query_length, metrics__height=query_height)
return context
#urls.py
????
#template.html
????
I saw in the django-geojson documentation multiple ways to hit the db (GeoJSON layer view,
Tiled GeoJSON layer view, GeoJSON template filter, low-level serialization). But I struggle to find the way to match my needs as my properties are in the Product Model, my coordinates are in the Location Model and my queryset in a non-related class-based view.
Any idea on the best way to perform my task? Should I continue with django-geojson or are there better apps for my purpose?
Your Product and Location look OK, but it is not clear what you are trying to do with Metrics. To select products near some place you want something like:
queryset = Product.objects.filter(location__geom__distance_lt=(someLocation, D(m=50)))
https://docs.djangoproject.com/en/3.0/ref/contrib/gis/geoquerysets/#distance-lt
Imagine, I have News models with many text fields
class News(models.Model):
title = models.CharField(max_length=255)
subtitle = models.CharField(max_length=255, blank=True)
lead = models.TextField(max_length=4096)
content = models.TextField()
...
last_visited = models.DateTimeField()
Every time my News object outputs, I update last_visited field:
news.last_visited = datetime.datetime.now()
news.save()
This code makes Django override all model fields:
UPDATE news SET title='...', subtitle='...', last_visited = '...' WHERE id = '...';
Instead of just one:
UPDATE news SET last_visited = '...' WHERE id = '...';
I worried how bad it is and is it worth of thinking about.
Django documentation offers queryset update but it looks not very elegant:
def upd(obj, **kwargs):
obj.__class__._default_manager.filter(pk=obj.pk).update(**kwargs)
upd(news, last_visited=datetime.datetime.now())
I use mysql backend.
Using update but with a cleaner approach:
class News(models.Model):
def update_visited(self):
News.objects.filter(pk=self.pk).update(
last_visited=datetime.datetime.now())
I think using queryset update is good. It removes the possibility that you overwrite changes to other fields by accident.
I know you're worried that it looks inelegant, but you only have to use it once in your upd function, then use upd in your views.
Supposing you want to use this on more than one model (guessing this because you pass obj to your upd function) it would probably make sense to have some base class that implements the last_visited field and your News class inherits from this class... Then you could do the update just on your base class.... Another possibilty would be putting the last_visited information into a seperate model and referencing the News model either through a ForeignKey or a GenericForeignKey (in the case you want to keep a 'history' for different models).