Adding default external network in docker-compose I am trying to learn docker and understanding docker-compose

As I was trying out the external network section:

 networks:
  default:
    external:
      name: my-pre-existing-network


I understand that 
'my-pre-existing-network' needs to be created.

Is it possible to create a new default external network from within the compose file itself?

This is more from a learning/understanding perspective. Thanks.
No that is not possible , it is called external because is created from outside the current docker-compose.yml you are working on