How to create set_facts variables ?

Create a ansible config file as ansible.cfg file in your project directory:

[defaults]  
inventory = hosts

Create a hosts file as hosts in the project directory:

[webservers]
ansnode1 ansible_ssh_host=192.168.56.202 ansible_python_interpreter=/usr/bin/python   
ansnode2 ansible_ssh_host=192.168.56.203 ansible_python_interpreter=/usr/bin/python   

[webservers:vars]
ansible_port=22  
http_port=8080  


[dbservers]
ansnode3 ansible_ssh_host=192.168.56.204 ansible_python_interpreter=/usr/bin/python    
ansnode4 ansible_ssh_host=192.168.56.205 ansible_python_interpreter=/usr/bin/python   

[dev:children]
webservers  
dbservers   

Create a file named called as set_facts_playbook.yml in your project directory

---
# YAML documents begin with the document separator ---    
the minus in YAML this indicates a list item. The playbook contains a list of plays, with each play being a dictionary       
# Target: where our play will run and options it will run with
- hosts: localhost
  # Task: the list of tasks that will be executed within the play,   this # section can also be used for pre and post tasks
  tasks:
    - name: set a fact
      set_fact:
        our_fact: Ansible Rocks!
    - name: show custom fact
      debug:
        msg: "{{ our_fact }}"  
# Three dots indicate the end of YAML document
...                  

Source Code Available in Github: https://www.github.com/tamiltutera