python实现下载文件路径自动添加(1)的递增路径

def is_file(file_name):
    if not os.path.exists(file_name):
        return file_name
    num = 1
    if re.findall("\((\d)\)", file_name):
        num = re.findall("\((\d)\)", file_name)
        new_num = int(num[0]) + 1
        file_name=file_name.replace(num[0],str(new_num))
        return is_file(file_name)
    path_list = file_name.split(".")
    file_name = path_list[0] + "({}).".format(num) + path_list[1]
    return is_file(file_name)


save_path=r"C:\temp\mail.eml"
res=is_file(save_path)
print(res)