Django calculate 2 values from model - django

Question

Im fairly new to Django. Im using Django 2.
My model:
# Create your models here.
class Trade(models.Model):
quantity = models.IntegerField()
open_price = models.FloatField()
commision = models.FloatField()
exchange_rate_usdsek = models.FloatField()
stock = models.ForeignKey(Stock, on_delete=models.CASCADE)
user = models.ForeignKey(User, related_name='trades', on_delete=models.PROTECT)
open_date = models.DateTimeField(auto_now_add=True, null=True)
def get_absolute_url(self):
return reverse('trade:detail',kwargs={'pk': self.pk})
def __str__(self):
return self.stock.name
My view
class IndexView(generic.ListView):
template_name = 'trade/index.html'
context_object_name = 'all_trades'
#
def get_queryset(self):
return Trade.objects.all()
#return Order.objects.all().prefetch_related('items')
def get_context_data(self, **kwargs):
context = super(IndexView, self).get_context_data(**kwargs)
return context
index.html
<h3>All stocks</h3>
<table class="table">
<thead>
<tr>
<th>Stock</th>
<th>Amount</th>
<th>Open Price</th>
<th>Commision</th>
<th>USD/SEK</th>
<th>Total sek</th>
</tr>
</thead>
{% for trade in all_trades %}
<tr>
<td>{{trade.stock.name}}</td>
<td>{{trade.quantity}}</td>
<td>{{trade.open_price}} USD</td>
<td>{{trade.commision}} SEK</td>
<td>{{trade.exchange_rate_usdsek}}</td>
<td>{{open_price * quantity * exchange_rate_usdsek}}</td>
</tr>
{% endfor %}
</table>
Now on my index.html I want to calculate and display a value.
I make a calculation like this:
total_sek = open_price * quantity * exchange_rate_usdsek
Do I have to calculate this in the views.py or in the index.html?
Also how would I do this? I searched around and found something about filters but im not sure if that is the right way to do it

Answer 1

The easiest way is to just define this calculation as a property on the model:
class Trade(models.Model):
# ...
#property
def total_sek(self):
return self.open_price * self.quantity * self.exchange_rate_usdsek
at which point you can simply
<td>{{ trade.total_sek }}</td>
in the template,
and trade.total_sek in Python code as required too.