Concatenate a complex string in Ansible

Constructing a long, complex string in Ansible can be achieved quite easily utilising Python string subsitution syntax.

Suppose you have the following variables:

app_protocol: http
app_host: 12.34.56.78
app_port: 8080
app_path: api/v2/testing

You could construct a string with all the components item by item using lots of "{{}}" syntax. Or, try this instead:

app_string: >-
  {{ "%s://%s:%d/%s"
        app_protocol,
        app_host,
        app_port,
        app_path
    ) }}

Note that %s is used for string interpolation and %dfor numeric or decimal values.

I think this is much more readable.