为什么Python在迭代时修改列表时会跳过元素？

my_list = [1, 2, 3, 4, 5]
new_list = [x * 2 for x in my_list]

my_list = [1, 2, 3, 4, 5]
for index, value in enumerate(my_list):
    my_list[index] = value * 2

my_list = [1, 2, 3, 4, 5]
for value in my_list.copy():
    my_list.append(value * 2)

my_list = [1, 2, 3, 4, 5]
for value in my_list[:]:
    my_list.append(value * 2)