Recursively formatting a dictionary of strings

I have a use-case where I'm using a dictionary as a basis for generating a configuration file, and many of the values in the file share pieces, such as URL bases or credentials. I will also be generating configuration files for several different instances from the same dictionary.

I wanted a simple way to define replaceable parts of the dictionary. I made a couple of Google searches, didn't find anything on the first page, so I wrote this:

gist for dict_format.py

I hope it's useful to someone else, or that I find it next time I have this use-case. :)