python查找列表中索引的边缘

my_list = [1, 2, 3, 4, 5, 3, 6, 7]
element = 3

try:
    start_index = my_list.index(element)
    end_index = len(my_list) - my_list[::-1].index(element) - 1
    print("索引的边缘为：", start_index, end_index)
except ValueError:
    print("列表中不存在该元素")

my_list = [1, 2, 3, 4, 5, 3, 6, 7]
element = 3

start_index = None
end_index = None

for index, value in enumerate(my_list):
    if value == element:
        if start_index is None:
            start_index = index
        end_index = index

if start_index is not None:
    print("索引的边缘为：", start_index, end_index)
else:
    print("列表中不存在该元素")