Use the attribute when to define that some task can just be executed when some conditional be attended. Following an example.
- name: Run tasks when userid exist include: tasks.yml vars: services: - firwalld - httpd when: userid is defined
- name: Copy file when the host is a webservice copy: src: files/index.html dest: /var/www/html/index.html when: inventory_hostname in groups["webservice"]
Check here the operators and see more about it in the Ansible docs.