dictionary-lookup.yml

---
- hosts: localhost
  gather_facts: no
  vars:
    database_clusters:
      - { cluster_name: "test_lon", port: 5433 }
      - { cluster_name: "prod_lon", port: 5434 }
  tasks:
    - name: Port for {{ environment }}_{{ region | lower }}
      debug: var="{{ database_clusters | selectattr('cluster_name', 'equalto', '{{ environment }}_{{ region | lower }}') | map(attribute='port') | join(',') }}"

# To run:
# ansible-playbook ./dictionary-lookup.yml --extra-vars="environment=test region=LON"