Sometimes, variables need to be modified. Essentially, you would like to call functions on these variables. Instead of chaining function calls, such as var.method1().method2(arg), Django uses the pipe syntax {{ var|method1|method2:"arg" }}, which is similar to Unix filters. However, this syntax only works for built-in or custom-defined filters.

Another limitation is that filters cannot access the template context. They only work with the data passed into them and their arguments. Hence, they are primarily used to alter the variables in the template context.

Run the following command in Python:

>>> title="SuperBook"
>>> title.upper()[:5]
'SUPER'

The following is its Django template equivalent:

{{ title|upper|slice:':5' }}"