如何返回sum函数的空值？

my_list = []  # 可迭代对象为空
if len(my_list) == 0:
    result = None  # 返回空值
else:
    result = sum(my_list)  # 计算总和

my_list = []  # 可迭代对象为空
try:
    result = sum(my_list)  # 计算总和
except ValueError:
    result = None  # 返回空值

def sum_with_empty(iterable):
    if len(iterable) == 0:
        return None  # 返回空值
    else:
        return sum(iterable)  # 计算总和

my_list = []  # 可迭代对象为空
result = sum_with_empty(my_list)  # 调用自定义函数