def get_file_ext(f):
    """
    takes in a filename.ext, finds extension by looking for the last . delimiter, and returns the filetype as str
    :param f:       str, required; filename with extension
    :return:        file extension
    """

    delim = f.rfind('.') + 1                            # locate the delimiter between the file name and file extension
    filetype = f[delim:]                                # grabs the substring after the delimiter

    return filetype