def base64_method(data_path, columns):
    data = pd.read_csv(data_path)
    data.dropna()
    data.reset_index(drop=True, inplace=True)
    existing_columns = list(data)
    for column in columns:
        if column in existing_columns:
            data[column] = data[column].apply(str)
            data[column] = data[column].apply(lambda x: base64.b64encode(bytes(x, 'utf-8')))
    return data