Jinja2: format + join the items of a list

Question

play_hosts is a list of all machines for a play. I want to take these and use something like format() to rewrite them like rabbitmq@%s and

Answer 1

You can create custom filter

# /usr/share/ansible/plugins/filter/format_list.py (check filter_plugins path in ansible.cfg)

def format_list(list_, pattern):
    return [pattern % s for s in list_]


class FilterModule(object):
    def filters(self):
        return {
            'format_list': format_list,
        }

and use it

{{ play_hosts | format_list('rabbitmq@%s') }}