Question

I have tried this a few ways. Per the docs, I have done this in my app’s ini:

[app:myapp]
#...
jinja2.filters =
    islist = myapp.machines.islist

My function is simply:

def islist(item):
    return isinstance(item, list)

I can tell the filter setup line in the ini file is being read, because if I get the dotted path to my islist function wrong, the app throws an error.

However, when I try to use the islist function in a template, the template can’t find the function.

{% if islist([]) %}a list{% else %}not a list{% endif %}

Results in this:

UndefinedError: 'islist' is undefined

What am I doing wrong?? Any help would be awesome.

Answer 1

I think filters are not exposed as functions in the namespace but rather are only invoked via the pipe. For example {{ foo | some_filter }}.