Thanks. I didn't know. This is weird behavior now that you've added the coordinate symbols. I would expect a for loop to iterate over them instead. For example, if I can do `N[0]`, `N[1]`, `N[3]`, then I would expect `for u in N` to give me the same thing that `N[i]` returns.

You can see that I advocated for the `__getitem__` to be used for unit vectors way back: https://github.com/sympy/sympy/pull/450#issuecomment-1775813

I'll update this.