如何使用django计算总价？

# models.py
from django.db import models

class Product(models.Model):
    name = models.CharField(max_length=100)
    price = models.DecimalField(max_digits=10, decimal_places=2)

# forms.py
from django import forms

class ProductForm(forms.Form):
    name = forms.CharField(max_length=100)
    quantity = forms.IntegerField()

# views.py
from django.shortcuts import render
from .models import Product
from .forms import ProductForm

def calculate_total_price(request):
    if request.method == 'POST':
        form = ProductForm(request.POST)
        if form.is_valid():
            product_name = form.cleaned_data['name']
            quantity = form.cleaned_data['quantity']
            try:
                product = Product.objects.get(name=product_name)
                total_price = product.price * quantity
                return render(request, 'total_price.html', {'total_price': total_price})
            except Product.DoesNotExist:
                error_message = "Product not found."
                return render(request, 'error.html', {'error_message': error_message})
    else:
        form = ProductForm()
    return render(request, 'calculate_total_price.html', {'form': form})

# calculate_total_price.html
<form method="post" action="{% url 'calculate_total_price' %}">
  {% csrf_token %}
  {{ form.as_p }}
  <button type="submit">Calculate</button>
</form>

# total_price.html
<p>Total Price: {{ total_price }}</p>

# error.html
<p>Error: {{ error_message }}</p>