python: how to have a property and with a setter function that detects all changes that happen to the value

Question

I have a two properties which holds lists. Whenever any item in this list changes, I would like the other list to update itself. This includes the statement obj.myProp

Answer 1

I recommend you look into using numpy. In particular, the transpose method gives a "view" of the underlying matrix with the axes transposed, meaning that if you change one then the other will change.

If that doesn't suit your needs, then the only way I can see to make the API you want work is to define the "rows" and "columns" methods to return custom "view objects" that don't actually store the data, but that point back to some private (shared) data in the grid object itself. These could be list-like, but would not support some operations (e.g., append or clear).