replace public ip from /etc/hosts file with private ip using Ansible

[BB]

I need to replace public ip from /etc/hosts file with private ip in bulk cluster of systems.

Ansible gathered fact , may work but not sure which is for what.

Another way, I can have public and private ip register as variable and swap them.

What would be the best practice to do in ansible way?

Currently in /etc/hosts 

________

public_ip   hostname short_hostname

I need to change it to 

private_ip  hostname short_hostname

[BB]

[ZillaYT]

Look at the "lineinfile" module.