Multiply in django template

Question

I am looping through cart-items, and want to multiply quantity with unit-price like this:

{% for cart_item in cart.cartitem_set.all %}
{{cart_item.quantity}}*{{cart_item.unit_price}}
{% endfor %}

Is it possible to do something like that? any other way to do it !! Thanks

possible duplicate of [multiplication in django template without using manually created template tag](http://stackoverflow.com/questions/18350630/multiplication-in-django-template-without-using-manually-created-template-tag) — Fernando Freitas Alves, Oct 25 '13 at 13:56
That's a clever use of a filter. I didn't think to use `cart_item.quantity` as the `value` and `cart_item.unit_price` as the `arg` — Brandon Taylor, Oct 25 '13 at 14:37

score 40 · Answer 1 · edited Feb 03 '19 at 19:39

40

You can use widthratio builtin filter for multiplication and division.

To compute A*B: {% widthratio A 1 B %}

To compute A/B: {% widthratio A B 1 %}

source: link

Notice: For irrational numbers, the result will round to integer.

edited Feb 03 '19 at 19:39

AppHandwerker

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answered Oct 22 '15 at 12:19

‌‌R‌‌‌.

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Way faster than writing a custom tag for a simple operation – D2TheC Dec 04 '15 at 07:58
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Doesn't seem to work for irrational values, ie, how do I multiply value by 1.5 (seems to truncate 1.5 to 1.0) – Nicholas Hamilton Feb 24 '16 at 01:32
@NicholasHamilton correct, I didn't notice that. the results will round to an integer. – ‌‌R‌‌‌. Feb 24 '16 at 04:44

score 21 · Accepted Answer · edited Nov 17 '19 at 00:30

You need to use a custom template tag. Template filters only accept a single argument, while a custom template tag can accept as many parameters as you need, do your multiplication and return the value to the context.

You'll want to check out the Django template tag documentation, but a quick example is:

from django import template
register = template.Library()

@register.simple_tag()
def multiply(qty, unit_price, *args, **kwargs):
    # you would need to do any localization of the result here
    return qty * unit_price

Which you can call like this:

{% load your_custom_template_tags %}

{% for cart_item in cart.cartitem_set.all %}
    {% multiply cart_item.quantity cart_item.unit_price %}
{% endfor %}

Are you sure you don't want to make this result a property of the cart item? It would seem like you'd need this information as part of your cart when you do your checkout.

score 14 · Answer 3 · answered Mar 11 '15 at 16:06

14

Or you can set the property on the model:

class CartItem(models.Model):
    cart = models.ForeignKey(Cart)
    item = models.ForeignKey(Supplier)
    quantity = models.IntegerField(default=0)

    @property
    def total_cost(self):
        return self.quantity * self.item.retail_price

    def __unicode__(self):
        return self.item.product_name

answered Mar 11 '15 at 16:06

Martin

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Logic better at the model, this is the correct answer – FireZenk Sep 11 '15 at 08:09
how to access this in django template direclty? – Manoj Sahu Nov 07 '15 at 16:06
Better solution, allows use of other filters – Giancarlo Ventura Nov 12 '19 at 17:38
@ManojSahu (for present readers, I hope you found out long ago :-): Just use `{{ cart_item.total_cost }}` – rapto Mar 12 '20 at 12:06

score -1 · Answer 4 · answered Oct 25 '13 at 11:11

You can do it in template with filters.

https://docs.djangoproject.com/en/dev/howto/custom-template-tags/#writing-custom-template-filters

From documentation:

Here’s an example filter definition:

def cut(value, arg):
    """Removes all values of arg from the given string"""
    return value.replace(arg, '')

And here’s an example of how that filter would be used:

{{ somevariable|cut:"0" }}

Multiply in django template

4 Answers4

Linked