String Formatting

[summer isle]

I want to make a string such as ```py
{{ "hello"|add:var.id }}

I want to use this to add an active class on a list item based on which page the user is on.

[wooden cradle]

You want to concatenate the string hello with the number in var.id ?

hello{{ var.id }} ?

[summer isle]

I want to use it in an if statement