CODEWITHSUNDEEP
djangodjango-templates
Yousuf Jawwad
Yousuf Jawwad

Reputation: 3097

doing something with a variable inside a block tag

lets say i am passing a variable "subtotal" inside a template using ..

in my views.py

subtotal = 0
page_vars = Context({
    'players': players,
    'subtotal': subtotal,
})

in my html.

{% for player in players %}
{% subtotal += player.score %}

{{ player.name }} <td />
{{ player.score }} <td />

{% endfor %}
{{ subtotal }}

it gives me

Invalid block tag: 'subtotal', expected 'empty' or 'endfor'

can't we have nested block tags in django templating system?

if yes, how?

there must be, as for me to calculate subtotal, i would have to calulate my subtotal, i have to run the same for loop at two places, which makes it highly ineffecient!

//mouse.

Upvotes: 0

Views: 255

Answers (2)

patrickn
patrickn

Reputation: 2561

I would really advise that you retain separation of logic and display of information. The Django template system is purposely designed to minimize your ability to shoot yourself in the foot by gumming up your templates with logic and calculations.

Perform your calculations and logical manipulation in the view, and pass the finished product to the template. The template language is there to help you maintain code reusability and "debuggability" by attempting to enforce this separation of responsibility.

Upvotes: 0

Burhan Khalid
Burhan Khalid

Reputation: 174624

You can have nested tags:

{% for foo in bar %}
   {% for zoo in foo %}
   {% endfor %}
{% endfor %}

To add something, you need the add template filter.

{{ player.score|add:subtotal }}

However, your problem needs to be resolved in the view. Since even with custom tags you cannot reliably keep track of a running total of a single variable in the template.

See this answer for an implementation to get you started, but note that they are talking about summing a list.

This kind of logic should be done in the view.

Upvotes: 1

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