I find it difficult to figure out what your trying to do. In either case, the items within the braces are format specifiers. Note that, if there was an f just before the opening quotation mark in the formatted string, that would create an f-string, which would make it search for a variable with that name.
"On two occasions I have been asked [by members of Parliament!]: 'Pray, Mr. Babbage, if you put into the machine wrong figures, will the right answers come out ?' I am not able rightly to apprehend the kind of confusion of ideas that could provoke such a question." — Charles Babbage.