我以前发生过这种情况，令人沮丧。

I've had this happen before and it's frustrating.

你的问题是这一行代码，这不是你所想的：

Your problem is this line of code, which isn't doing what you think it is:

loc1 = [[0.0] * ncols] * nrows

[0.0] * ncols 创建一个单独的列表，通过引用传递以形成您的2D列表。

[0.0] * ncols creates a single list which is passed by reference to form your 2D list.

尝试这样：

loc1 = [[0.0 for y in range(ncols)] for x in range(nrows)]