How to pass hostname to playbook in ansible playbook

[Swordfish Binary]

1. I have a requirement where I need to pass a hostname so that the ansible playbook can take the hostname and do the necessary actions like stopping and starting the service of a application.

How can I pass hostname that comes externally to the ansible playbook? 

- hosts: all

  gather_facts: true

  tasks:

    - name: Set services on job servers in {{ work_env }} to {{ work_op }}

      service:

        name: "{{ item }}"

        state: "{{ work_op }}"

      when:

        - inventory_hostname in groups[work_env]

        - inventory_hostname in groups["job"]

      loop:

        - rdcstop

        - ratstop

      loop_control:

        label: Set {{ item }} service on {{ inventory_hostname }} to {{ work_op }}.

Here in the above work_env,work_op all are defined in my template. The "job" is defined in my inventory file, this tells what host will fall under the "jobs" category.  So, if I remove the inventory file, how will ansible will be able to read the hostname that comes from external calls?