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I am learning Django and creating a cart application. What I am trying to do here is to display on the HTML page the sum of all the cart items 'prices'.
Now, I know this is probably the worst way to do it, as I have seen many tutorials, but I'd rather learn step by step.
So what I am doing here is setting the variable 'total' equal to the sum of all prices using the Sum() function documented here.
The problem is that it displays a number with 13 decimal places, although my model allows just 2 decimal places. How can I overcome this issue?
Here is all the code, and obviously If you have any tip about a better 'basic' way to do this (a best practice) please let me know in the comments.
'models.py'
from django.db import models
from django.contrib.auth.models import User
# Create your models here.
class Item(models.Model):
name = models.CharField(max_length=25)
price = models.DecimalField(max_digits=5, decimal_places=2)
def __str__(self):
return self.name
class Cart(models.Model):
user = models.ForeignKey(User, on_delete=models.CASCADE)
created_at = models.DateTimeField(auto_now_add=True)
items = models.ManyToManyField(Item)
def __str__(self):
return 'Order number: %s' % self.id
'views.py'
from django.shortcuts import render
from .models import Cart, Item
from django.db.models import Sum
# Create your views here.
def home(request):
items = Item.objects.all()
carts = Cart.objects.all()
length = len(Cart.objects.all())
cart = carts[length - 1]
cart_items = cart.items.all()
total = cart_items.aggregate(Sum('price'))['price__sum']
return render(request, 'cart/home.html', {'cart': cart,
'items': items,
'cart_items': cart_items,
'total': total})
and my 'home.html'
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Home page</title>
</head>
<body>
<div><h1>Menu</h1></div>
{% for item in items %}
<ul>{{ item }} £{{ item.price}} <button>Add</button></ul>
{% endfor %}
<div><h1>Order</h1></div>
{{ cart }}
{% for item in cart_items %}
<ul>{{ item.name }} {{ item.price }}</ul>
{% endfor %}
<h2>Total</h2>
{{ total }}
</body>
</html>
703
asked Sep 05 '25 03:09
If you're using SQLite, you should know that it doesn't support decimal internally, as explained here. That's why Sum() returns a float.
You should therefore either use python float formatting functions to round total to 2 decimals or you can use the floatformat template filter.
194
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