Convert Ansible YAML inventory to JSON using Python

python3 -c 'import sys, yaml, json; json.dump(yaml.load(sys.stdin, Loader=yaml.FullLoader), sys.stdout, indent=4)' < hosts.yaml > hosts.json

Check if new JSON inventory is correct:

ansible all -i hosts.json --list-hosts

So the inventory in YAML:

--- # start
control:
  hosts:
    ubuntu-c:
      ansible_connection: local
centos:
  hosts:
    centos1:
      ansible_port: 2222
    centos2:
    centos3:
  vars:
    ansible_user: root
ubuntu:
  hosts:
    ubuntu1:
    ubuntu2:
    ubuntu3:
  vars:
    ansible_become: true
    ansible_become_pass: password
linux:
  children:
    centos:
    ubuntu:
... # end

Becomes the following inventory in JSON:

{
    "control": {
        "hosts": {
            "ubuntu-c": {
                "ansible_connection": "local"
            }
        }
    },
    "centos": {
        "hosts": {
            "centos1": {
                "ansible_port": 2222
            },
            "centos2": null,
            "centos3": null
        },
        "vars": {
            "ansible_user": "root"
        }
    },
    "ubuntu": {
        "hosts": {
            "ubuntu1": null,
            "ubuntu2": null,
            "ubuntu3": null
        },
        "vars": {
            "ansible_become": true,
            "ansible_become_pass": "password"
        }
    },
    "linux": {
        "children": {
            "centos": null,
            "ubuntu": null
        }
    }
}