Numpy: views vs copy by slicing

Question

When I am doing the slicing, an unexpected thing happened that seems the first to be view but the second is copy.

First

First slice of row, then slice of

Answer 1

The accepted answer by John Zwinck is actually false (I just figured this out the hard way!). The problem in the question is a combination of doing "lvalue indexing" with numpy's fancy indexing. The following doc explains exactly this case

https://scipy-cookbook.readthedocs.io/items/ViewsVsCopies.html

in the section "But fancy indexing does seem to return views sometimes, doesn't it?"