How to run an Ansible playbook locally

• using Ansible command line:

ansible-playbook --connection=local 127.0.0.1 playbook.yml

• using inventory:

127.0.0.1 ansible_connection=local

• using Ansible configuration file:

[defaults]
transport = local

• using playbook header:

- hosts: 127.0.0.1
  connection: local

The first option only works as ansible-playbook --connection=local --inventory 127.0.0.1, playbook.yml
Comma is essential, otherwise it's treated like file name.