Append() changes the shape of class list?

I apologise if this is in the wrong place.

I need to append() my test numpy array to my history class list and it changes the shape of history from (30, 72, 7) to (31,). At least that’s what it appears like. Why is this? It, later on, causes a tuple out of range when trying to flatten the data.

Thank you in advance.

Do you have a minimal Colab or a code snippet to reproduce this?

Hello! I appreciate your reply and attempt to help. It turns out I was misled by someone on how to preprocess my CNN model. Hence nothing was working as intended.