Develop Reference

Django and use calculated values in QuerySet

I have a function to convert net to gross price like this.
taxRate is the tax value. e.g. 23, 8, 5, 0
def gross(netValue, taxRate: int, currencyPrecision=2):
if taxRate > 0:
return round(netValue * (100 + taxRate) / 100, currencyPrecision)
else:
return round(netValue, currencyPrecision)
In my model I have a class that is order items with fields: netPrice and taxId.
class OrderPosition(models.Model):
posNumber = models.AutoField(auto_created=True, primary_key=True, editable=False, blank=False)
order = models.ForeignKey(OrderHeader, on_delete=models.PROTECT)
product = models.ForeignKey(Product, on_delete=models.PROTECT)
quantity = models.DecimalField(blank=False, max_digits=3, decimal_places=0)
netPrice = MoneyField(blank=False, max_digits=6, decimal_places=2, default=Money("0", "PLN"))
taxId = models.IntegerField(blank=False, default=0)
The value of the entire order with a given ID can be calculated as follows:
def getNetValue(self):
posList = OrderPosition.objects.filter(order_id=self.orderID)
if posList:
return str(posList.aggregate(netValue=Sum(F('quantity') * F('netPrice'),
output_field=MoneyField()))['netValue'])
else:
return "0"
Question: Can I use my function "gross()" in a query to calculate the gross value of an order in a similar way to calculate the net worth?
I suppose the aggregation function is performed on the database side (mySQL in my case) and we can only use what is understandable at the database and SQL level.

Try this:
net_value = OrderPosition.objects.filter(order_id=self.order_id).aggregate(
net_value=Sum(F('quantity') * F('net_price'), output_field=MoneyField())
)['net_value']
tax_rate = OrderPosition.objects.filter(order_id=self.orderID) \
.values('taxId')[0]['taxId']
gross_value = gross(net_value, tax_rate)
we need to iterate over the order item and calculate the gross for each item like this:
total_gross_value = Money(0, "PLN")
for order_item in OrderPosition.objects.filter(order_id=self.order_id):
net_price = order_item.net_price
tax_rate = order_item.tax_id
gross_price = gross(net_price, tax_rate)
total_gross_value += gross_price
we can use annotate method on queryset like this:
from django.db.models import F, Func
class GrossValue(Func):
function = 'ROUND'
template = '%(function)s(%(expressions)s * (100 + %(tax_rate)s) / 100, 2)'
def __init__(self, expression, tax_rate, **extra):
super().__init__(expression, tax_rate=tax_rate, **extra)
OrderPosition.objects.filter(order_id=self.order_id).annotate(
gross_price=GrossValue(F('net_price'), F('tax_id'))
).aggregate(Sum('gross_price'))
have a nice day ;)

python mongoengine EmbeddedDocumentListField and aggregate

I wanna now if MongoEngine aggregate() functionality only works on QuerySet?
well, this is the project I'm working on
#imports
class Status(Enum):
ACTIVE = "active"
CLOSED = "closed"
class OrderType(Enum):
BUY = "buy"
SELL = "sell"
class Order(EmbeddedDocument):
type = EnumField(OrderType, required=True)
vol = IntField(required=True)
time = DateTimeField(required=True, default=datetime.now())
class Stock(EmbeddedDocument):
name = StringField(max_length=20, required=True)
orders = EmbeddedDocumentListField(Order, required=True)
status = EnumField(Status, required=True, default=Status.ACTIVE)
amount = IntField(required=True, default=0)
pnl = FloatField()
class Portfolio(Document):
account = IntField(required=True, unique=True)
stocks = EmbeddedDocumentListField(Stock, required=True)
balance = FloatField()
equity = FloatField()
I want to be able to make Stock.amount field be an aggregation of Order.vol which, as can be seen, is an EmbeddedDocumentListField of stock. I already know about mongoengine.signals and seen examples on aggregate(), but all of them use aggregate() on QuerySet returned by .objects(). So what is the tweak for it? Many Thanks.

Currently I come up with this:
def handler(event):
def decorator(fn):
def apply(cls):
event.connect(fn, sender=cls)
return cls
fn.apply = apply
return fn
return decorator
#handler(signals.post_init)
def update_amount(sender, document):
orders = document.orders
amnt = 0
for order in orders:
if order.type == OrderType.Buy:
amnt += order.vol
else:
amnt -= order.vol
document.amount = amnt
and then I added decorator #update_amount.apply to my Stock class. but it would work nicer with aggregate if it's possible

Django import export edit queryset before export

I'm trying to calculate the pending amount via models and export result in the csv. But the csv shows an empty column for amountpending
class FinancePendingResource(resources.ModelResource):
invoiceNumber = Field(attribute='invoiceNumber', column_name='Invoice Number')
student = Field(attribute='student', column_name='Student')
Schedule = Field(attribute='Schedule', column_name='Schedule')
TotalAmount = Field(attribute='TotalAmount', column_name='Total Value(PKR ₨)')
issueDate = Field(attribute='issueDate', column_name='Issue Date')
dueDate = Field(attribute='dueDate', column_name='Due Date')
amountPaid = Field(attribute='amountPaid', column_name='Amount Paid (PKR ₨)')
class Meta:
model = FinancePending
import_id_fields = ('invoiceNumber',)
fields = ('invoiceNumber', 'student', 'amountPaid', 'issueDate', 'dueDate', 'Schedule', 'TotalAmount',
'AmountPending',)
exclude = ('id',)
skip_unchanged = True
report_skipped = True
def before_export(self, queryset, *args, **kwargs):
amount_paid = FinancePending.objects.values_list('amountPaid', flat=True)
amount_paid = list(amount_paid)
total_amount = FinancePending.objects.values_list('TotalAmount', flat=True)
total_amount = list(total_amount)
# total - paid
TotalFee = [float(s.replace(',', '')) for s in total_amount]
AmountPaid = [float(s.replace(',', '')) for s in amount_paid]
def Diff(li1, li2):
return (list(set(li1) - set(li2)))
amount_pending = Diff(TotalFee, AmountPaid)
finance_pending = FinancePending()
i = 1
while i <= len(amount_pending):
FinancePending.objects.filter(invoiceNumber=i).update(AmountPending=str(amount_pending[i]))
i = i + 1
queryset.refresh_from_db()

Assuming that you have the data to compute amountPending already in the dataset, perhaps you don't need to read from the DB: you could calculate the amount by processing the dataset in memory. This could be done in after_export(). Then you can added the computed column to the dataset.
Perhaps tablib's dynamic columns can assist in adding the amountPending column:
import decimal
import tablib
headers = ('invoiceNumber', 'amountPaid', 'totalAmount')
rows = [
('inv100', '100.00', "500.00"),
('inv101', '200.00', "250.00")
]
def amount_pending(row):
return decimal.Decimal(row[2]) - decimal.Decimal(row[1])
data = tablib.Dataset(*rows, headers=headers)
data.append_col(amount_pending, header="amountPending")
print(data)
This will produce the following:
invoiceNumber|amountPaid|totalAmount|amountPending
-------------|----------|-----------|-------------
inv100 |100.00 |500.00 |400.00
inv101 |200.00 |250.00 |50.00

Django not finding command when importing CSV data with Dictreader

I would like to use Python's Dictreader to import a csv file based on my Django model into the database.
My post model is:
class Post(models.Model):
STATUS_CHOICES = (
("draft", "Draft"),
("published", "Published")
);
slug = models.SlugField(max_length=250);
wine_id = models.IntegerField();
country = models.CharField(max_length=100);
description = models.TextField();
designation = models.TextField();
price = models.FloatField();
province = models.CharField(max_length=100);
region_1 = models.CharField(max_length=100);
region_2 = models.CharField(max_length=100);
variety = models.CharField(max_length=100);
winery = models.CharField(max_length=100);
objects = models.Manager();
class Meta:
ordering = ("id",);
def __str__(self):
return self.variety;
def get_absolute_url(self):
return reverse("post_detail", args=[self.id,
self.province,
self.slug]);
My script to read the csv data is:
class Command(BaseCommand):
# Shows this when the user types help:
help = "Loads data from wine_data.csv into our Post model.";
def handle(self, *args, **kwargs):
if Post.objects.exists():
print("Wine data already loaded... exiting...");
print(ALREADY_LOADED_ERROR_MESSAGE);
return;
print("Loading wine data for WCC.");
for row in DictReader(open("wine_data.csv")):
post = Post();
post.wine_id = row["wine_id"];
post.country = row["country"];
post.description = row["description"];
post.designation = row["designation"];
post.price = row["price"];
post.province = row["province"];
post.region_1 = row["region_1"];
post.region_2 = row["region_2"];
post.variety = row["variety"];
post.winery = row["winery"];
post.save();
However, when I use "python manage.py load_wine_data", the cmd says it is an unknown command. What am I doing wrong and how can I solve it?

Create error message datefield

I want to create an error message for following form:
class ExaminationCreateForm(forms.ModelForm):
class Meta:
model = Examination
fields = ['patient', 'number_of_examination', 'date_of_examination']
Models:
class Patient(models.Model):
patientID = models.CharField(max_length=200, unique=True, help_text='Insert PatientID')
birth_date = models.DateField(auto_now=False, auto_now_add=False, help_text='YYYY-MM-DD')
gender = models.CharField(max_length=200,choices=Gender_Choice, default='UNDEFINED')
class Examination(models.Model):
number_of_examination = models.IntegerField(choices=EXA_Choices)
patient = models.ForeignKey(Patient, on_delete=models.CASCADE)
date_of_examination = models.DateField(auto_now=False, auto_now_add=False, help_text='YYYY-MM-DD')
Every Patient has 2 Examinations (number of examination = Choices 1 or 2) and the error message should be activated when the date of the second examination < date of the first examination. Something like this:
Solution: `
def clean_date_of_examination(self):
new_exam = self.cleaned_data.get('date_of_examination')
try:
old_exam = Examination.objects.get(patient=self.cleaned_data.get('patient'))
except Examination.DoesNotExist:
return new_exam
if old_exam:
if old_exam.date_of_examination > new_exam:
raise forms.ValidationError("Second examination should take place after first examination")
return new_exam`

def clean_date_of_examination(self):
new_exam = self.cleaned_data.get('date_of_examination')
old_exam = Examination.objects.get(patient = self.cleaned_data.get('Patient'))
if old_exam:
if old_exam.date_of_examination > new_exam.date_of_examination:
raise forms.ValidationError("Second examination should take place after first examination")
return data

def clean_date_of_examination(self):
# Where 'data' is used?
date_of_exam = self.cleaned_data['date_of_examination']
try:
pat1 = Patient.object.get(examination__number_of_examination=1, date_of_examination=date_of_exam)
except Patiens.DoesNotExist:
# Patient 1 with given query doesn't exist. Handle it!
try:
pat2 = Patient.object.get(examination__number_of_examination=2, date_of_examination=date_of_exam)
except Patiens.DoesNotExist:
# Patient 2 with given query doesn't exist. Handle it!
if pat2.date_of_examination < pat1.date_of_examination:
raise forms.ValidationError("Second examination should take place after first examination")`
return data`