_f_lookup = {
    "some arbitrary f-string {foo} {bar} {g}": "translated {bar} {g!r} {foo}",
    "school {school}": "escuela {school}",
}

_f_cache = {}


def _f(s):
    # Find the translated string.
    translated = _f_lookup[s]

    # See if we're already compiled this.
    result = _f_cache.get(translated)
    if result is not None:
        return result

    # Convert to an f-string, then compile it, cache it, and return it.
    c = compile(f"f{translated!r}", filename=translated, mode="eval")
    _f_cache[translated] = c
    return c


# Some function that contains an "f-string" that needs translating.
def fn(foo):
    bar = 100
    return eval(_f("some arbitrary f-string {foo} {bar} {g}"))


g = "a global"
print(fn(200))

g = 3.1415
print(fn(300))