[Ansible] – How to define a list of values in the YAML files?

The list can be informed like the following example.

  hosts:
    - servera.example.com
    - serverb.example.com
    - serverc.example.com

Also, it can be done in the same line by using the characters ([]).

hosts: [servera.example.com, serverb.example.com, serverc.example.com]

For further information, check YAML Syntax in the Ansible documentation.