converters = {func.__name__[0]: func for func in (str, repr, ascii)} converters[None] = str parts = [] for part in t_string: match part: case Interpolation(value, _, conversion, format_spec): parts.append(format(converters[conversion](value), format_spec)) case str(): parts.append(part) return "".join(parts) if __name__ == "__main__": name = "world" expected = f"Hello, {name}!