list1:
  - { endpoint: {address: "addr1", port: "port1"}}
  - { endpoint: {address: "addr2", port: "port2"}}

elasticache_facts:
  region: "{{ terraform.region }}"
  name: "{{ cluster }}-{{ env }}"
register: elasticache

#declare an empty var in vars file to be used as accumulator
memcache_hosts: ""

# iterate through the list of nodes and append the fields to my string; I will have some extra spaces(separators) but that's ok
set_fact:
  memcache_hosts: "{{ memcache_hosts }} {{item.endpoint.address}}:{{item.endpoint.port}}"
with_items: "{{ elasticache.elasticache_clusters[0].cache_nodes}}"```

Is there some less ugly way to filter the list to the desired format?
Maybe there is a magic filter I don't know about.
I can also obtain two lists, one with hosts, one with ports, zip them, make a dict out of that, but I found only some ugly to_json and then regex to make it a string.
I am also considering to write a custom filter in python, but seems also overdoing it.

Thanks for the help!