How to use placeholder inside brackets in python?

Question

Today I was wondering about the limitations of python formatting of strings. For example, say you want to build this kind of string : ${SOME_APPLICATION_VAR}

If SOME_APPLICATION_VAR is not known in advance, how would you build this string ?

I tried "${{}}".format(variable_name) but it yields ${}. I understand why but I can't find a way to achieve my goal. A lot of attempts were awarded with exceptions.

Could someone give me some clues about how to do that ?

Answer 1

You need to use 3 of each bracket. 2 get resolved into a literal set of brackets, and the last set acts as the placeholder for the formatting.

print("${{{}}}".format(variable_name))