I have a a form in Django with two inline forms. One of them is giving me grief.
My model is like so.
class BookingActivity(models.Model):
booking = models.ForeignKey('Booking')
program = models.ForeignKey(Program)
activity = models.ForeignKey(Activity, choices=programs_as_optgroups())
the activity ForeignKey choices are generated via this method:
def programs_as_optgroups():
activities = []
programs = []
for program in Program.objects.all():
new_program = []
new_activities = []
for activity in Activity.objects.filter(program=program):
new_activities.append([activity.id, activity.name])
new_program = [program.name, new_activities]
activities.append(new_program)
return activities
I'm trying to add <optgroup> tags to my ForeignKey select which is working. But when I submit the form I get an error: Cannot assign "u'3'": "BookingActivity.activity" must be a "Activity" instance.
This makes some sense - sort of. But if I check the request data sent from the form post. With choices either setup or not I get the same values, i.e.
activity = models.ForeignKey(Activity, choices=programs_as_optgroups())
and
activity = models.ForeignKey(Activity)
both return the a u'3' from the form. But I can't figure out why I get an error only when I'm using the optgroups.
I'm guessing you're trying
http://dealingit.wordpress.com/2009/10/26/django-tip-showing-optgroup-in-a-modelform/
in the blog
sub_categories.append([sub_category.id, sub_category.name])
you have
new_activities.append([activity.id, activity])
I think you're assuming you will get an object when it actually is a string you're getting back.
Related
Two models Users (built-in) and Posts:
class Post(models.Model):
post_date = models.DateTimeField(default=timezone.now)
user = models.ForeignKey(User, on_delete=models.CASCADE, null=True, related_name='user_post')
post = models.CharField(max_length=100)
I want to have an API endpoint that returns the percentage of users that have posted. Basically I want SUM(unique users who have posted) / total_users
I have been trying to play around with annotate and aggregate, but I am getting the sum of posts for each users, or the sum of users per post (which is one...). How can I get the sum of posts returned with unique users, divide that by user.count and return?
I feel like I am missing something silly but my brain has gone to mush staring at this.
class PostParticipationAPIView(generics.ListAPIView):
queryset = Post.objects.all()
serializer_class = PostSerializer
def get_queryset(self):
start_date = self.request.query_params.get('start_date')
end_date = self.request.query_params.get('end_date')
# How can I take something like this, divide it by User.objects.all().count() * 100, and assign it to something to return as the queryset?
queryset = Post.objects.filter(post_date__gte=start_date, post_date__lte=end_date).distinct('user').count()
return queryset
My goal is to end up with the endpoint like:
{
total_participation: 97.3
}
Thanks for any guidance.
BCBB
EDIT
OK, I am still struggling a bit. I tried to create a serializer that just had a decimal field for participation_percentage like:
percentage_participation = serializers.DecimalField(max_digits=5, decimal_places=2, max_value=100, min_value=0)
Then I calculate in the view, but I get an error:
Got AttributeError when attempting to get a value for field percentage_participation on serializer ParticipationSerializer.
The serializer field might be named incorrectly and not match any attribute or key on the str instance.
Original exception text was: 'str' object has no attribute 'percentage_participation'.
Error was the same if I made it a CharField (in case there was some string coercion?).
So then I tried to move it to a Serializer Method and put all the calculation logic in there. This calculated fine, but if I had to provide a query_set in the view. If provided a model object, it just returned the percentage as many times as the query (say Posts.objects.all() had a total of 100 posts, it returned the percentage 100 times).
So then I tried to override the get_queryset in the view, but I HAVE to return something. If I just return { "meh", "hello" } then I return the percentage from the SerializerMethodField one time and the end result is exactly what I want.
I just have no idea as to WHY or how to do this correctly.
Thanks for your help.
EDIT #2
OK so I realized why I was only getting one, it was iterating over the string I returned, which was one character. When I returned "meh" it gave me three of the percentage, iterating over each character in the string...
I am not understanding from playing around, reading the docs, or using GoogleFu how to do this properly. I just want to be able to perform some kind of summary logic on records from the DB - how can I do this properly?!?!
Thank you for all your time.
BCBB
something like this should work
# get total user count
total_users = User.objects.count()
# get unique set of users with post
total_users_who_posted = Post.objects.filter(...).distinct("user").count()
# calculate_percentage
percentage = {
"total_participation": (total_users_who_posted*100)/ total_users
}
# take caution of divion by zero
I don't think it is possible to use djangos orm to do this completely but you can use the orm to get the user counts (with posts and total):
from django.db.models import BooleanField, Case, Count, When, Value
counts = (User
.objects
.annotate(posted=Case(When(user_post__isnull=False,
then=Value(True)),
default=Value(False),
output_field=BooleanField()))
.values('posted')
.aggregate(posted_users=Count('pk', filter=Q(posted=True)),
total_users=Count('pk', filter=Q(posted__isnull=False)))
# This will result in a dict containing the following:
# counts = {'posted_users': ...,
# 'total_users': ....}
Would like to be able to access data in a post request directly as well as processing it in the normal way. First created form:
class TransactionForm(ModelForm):
class Meta:
model = Transaction
fields = ['dish', 'customer', 'grams', 'amount_payable']
('customer' is the pk of another model, Customer.)
Then process form:
#csrf_exempt
def create_transaction(request):
print(request.POST)
user_input = TransactionForm(request.POST)
print (user_input)
if user_input.is_valid():
user_input.save()
#customerobject = Customer.objects.get(pk= PK-TAKEN FROM POST)
#customerobject.account_balance -= (amount_payable TAKEN FROM POST)
#customerobject.save()
return HttpResponse('AOK~')
else:
return HttpResponse(user_input) #'ERROR: transaction not valid~')
Am struggling to correctly formulate the commented lines above. (The rest works fine.)
Would like to be able to extract the value 'customer' from the POST in order to find the customer. Then to extract the value 'amount_payable' from the POST in order to deduct it from the customer's balance.
Eventually stumbled upon the relevant command:
cust = user_input.cleaned_data.get('customer')
customerobject = Customer.objects.get(pk=cust.id)
customerobject.account_balance -= user_input.cleaned_data.get('amount_payable')
customerobject.save()
Low-level languages are easier for sieve-heads like me.
I am having trouble with updating fields of a model instance. The model is as follows:
class commonInfo(models.Model):
mothers_id = models.IntegerField(primary_key=True)
date = models.DateField()
data_collector = models.CharField(max_length=50)
Essentially, I just want to do this, but it won't work because commonInfo has a user defined primary key
commonInfo_form(request.POST or None).is_valid()
Since I am updating, I am overriding date and data_collector, but not mothers_id. So I would want to do something like this, but this specific code is not working
obj = commonInfo.objects.get(pk=commonInfo_id)
form = commonInfo_form(request.POST)
date = form.cleaned_data['data_collector'] #this line is not working
data_collector = form.cleaned_data['data_collector'] #this line is not working
obj.update(**{'date':date, 'data_collector':data_collector})
any ideas? I feel like it is just those two lines that I need to fix. Or if there is a more pythonic way or built method in Django?
Just validate with isinstance. so like,
if isinstance(request.POST['date'], datetime.date) and isinstance(request.POST['data_collector'], str):
# you might have to use getattr for request.POST here, I'm not sure
# and request.POST['date'] would have to be converted from a string to datetime.date I think
date = request.POST['date']
data_collector = request.POST['data_collector']
obj.update(**{'date':date, 'data_collector':data_collector})
The process for adding a record from a form is different from updating an existing instance. All you need to do differently is indicate which instance to bind the form to when you create it, ex:
obj = commonInfo.objects.get(pk=commonInfo_id)
form = commonInfo_form(request.POST, instance=obj)
I have two models:
Base_Activity:
topics = models.ManyToManyField(Topic)
... some others
User_Activity:
user = models.ForeignKey(settings.AUTH_USER_MODEL)
activity = models.ForeignKey(Base_Activity)
is_archived = models.BooleanField(default=False)
Now I want to query Base_activity to select all rows with topic X and exclude any rows that have a matching row in User_Activity for user=*current_user* and is_archived=True.
I have read the Django docs on how to follow relationships backward, since I query Base_Activity, but need information from User_Activity which has a ForeignKey to the former. However, even testing this method in the Django console doesn't work:
a = Base_Activity.objects.filter(topics__slug = topic)
a.user_activity_set.all()
AttributeError: 'InheritanceQuerySet' object has no attribute 'user_activity_set'
Question: What is the best way to do my query? If this is indeed by following the ForeignKey backwards, then what am I doing wrong?
a = Base_Activity.objects.filter(topics__slug = topic)
This returns a QuerySet instance, not a model instance. You should iterate through it or just get one from the list:
activities = Base_Activity.objects.filter(topics__slug=topic)
activities[0].user_activity_set.all()
In your case you can do entire work in one query:
activities = Base_Activity.objects.filter(topics__slug=topic).exclude(user_activity__user=user, user_activity__is_archived=True)
I'm not sure this will solve your problem, but anyway please don't use underscores in your class names in Python.
Is there an easy way to fetch the ManyToMany objects from a query that returns more than one object? The way I am doing it now doesn't feel as sexy as I would like it to. Here is how I am doing it now in my view:
contacts = Contact.objects.all()
# Use Custom Manager Method to Fetch Each Contacts Phone Numbers
contacts = PhoneNumber.objects.inject(contacts)
My Models:
class PhoneNumber(models.Model):
number = models.CharField()
type = models.CharField()
# My Custom Manager
objects = PhoneNumberManager()
class Contact(models.Model):
name = models.CharField()
numbers = models.ManyToManyField(PhoneNumber, through='ContactPhoneNumbers')
class ContactPhoneNumbers(models.Model):
number = models.ForeignKey(PhoneNumber)
contact = models.ForeignKey(Contact)
ext = models.CharField()
My Custom Manager:
class PhoneNumberManager(models.Manager):
def inject(self, contacts):
contact_ids = ','.join([str(item.id) for item in contacts])
cursor = connection.cursor()
cursor.execute("""
SELECT l.contact_id, l.ext, p.number, p.type
FROM svcontact_contactphonenumbers l, svcontact_phonenumber p
WHERE p.id = l.number_id AND l.contact_id IN(%s)
""" % contact_ids)
result = {}
for row in cursor.fetchall():
id = str(row[0])
if not id in result:
result[id] = []
result[id].append({
'ext': row[1],
'number': row[2],
'type': row[3]
})
for contact in contacts:
id = str(contact.id)
if id in result:
contact.phonenumbers = result[id]
return contacts
There are a couple things you can do to find sexiness here :-)
Django does not have any OOTB way to inject the properties of the through table into your Contact instance. A M2M table with extra data is a SQL concept, so Django wouldn't try to fight the relations, nor guess what should happen in the event of namespace collision, etc... . In fact, I'd go so far as to say that you probably do not want to inject arbitrary model properties onto your Contact object... if you find yourself needing to do that, then it's probably a sign you should revise your model definition.
Instead, Django provides convenient ways to access the relation seamlessly, both in queries and for data retrieval, all the while preserving the integrity of the entities. In this case, you'll find that your Contact object offers a contactphonenumbers_set property that you can use to access the through data:
>>> c = Contact.objects.get(id=1)
>>> c.contactphonenumbers_set.all()
# Would produce a list of ContactPhoneNumbers objects for that contact
This means, in your case, to iterate of all contact phone numbers (for example) you would:
for contact in Contact.objects.all():
for phone in contact.contactphonenumbers_set.all():
print phone.number.number, phone.number.type, phone.ext
If you really, really, really want to do the injection for some reason, you'll see you can do that using the 3-line code sample immediately above: just change the print statements into assignment statements.
On a separate note, just for future reference, you could have written your inject function without SQL statements. In Django, the through table is itself a model, so you can query it directly:
def inject(self, contacts):
contact_phone_numbers = ContactPhoneNumbers.objects.\
filter(contact__in=contacts)
# And then do the result construction...
# - use contact_phone_number.number.phone to get the phone and ext
# - use contact_phone_number.contact to get the contact instance