returns a so called wave of a given string wave cat cat cat cat wave one one one one wave book book book book book returns a so called wave of a given string wave cat cat cat cat wave one one one one wave book book book book book
def wave(txt: str) -> list:
    

    return [
        txt[:a] + txt[a].upper() + txt[a + 1 :]
        for a in range(len(txt))
        if txt[a].isalpha()
    ]


if __name__ == "__main__":
    __import__("doctest").testmod()