Python 列表是可变对象，这里:

Python lists are mutable objects and here:

plot_data = [[]] * len(positions) 

您正在重复相同的列表 len(positions) 次.

you are repeating the same list len(positions) times.

>>> plot_data = [[]] * 3
>>> plot_data
[[], [], []]
>>> plot_data[0].append(1)
>>> plot_data
[[1], [1], [1]]
>>> 

列表中的每个列表都是对同一对象的引用.你修改一个，你会看到所有的修改.

Each list in your list is a reference to the same object. You modify one, you see the modification in all of them.

如果你想要不同的列表，你可以这样做:

If you want different lists, you can do this way:

plot_data = [[] for _ in positions]

例如:

>>> pd = [[] for _ in range(3)]
>>> pd
[[], [], []]
>>> pd[0].append(1)
>>> pd
[[1], [], []]