IIRC, they're syntactic sugar over "string".format(locals())
https://docs.python.org/3/library/string.html#format-string-... https://docs.python.org/3/reference/lexical_analysis.html#f-...
https://docs.python.org/3/library/string.html#format-string-... https://docs.python.org/3/reference/lexical_analysis.html#f-...