How to count items in a shortcode with data-driven

I have a working simple shortcode to display a list of cities/countries from a json file (places.json).
The code is as follows:

{{ range .Site.Data.places }}
{{ $p := . }}
<li>{{ $ }} - <strong>{{ $ }}</strong> </li>
{{ end }}

I would like to know how to count and display the total number of cities for each given country and the total number of countries
Thank you

Take a gander at len:

Thanks for the guidance but as newbie and after several unsuccessful tests I am not able to built the correct syntax to achieve what I want.