Python numpy: column arrays (2d) or lists (1d)
Depends on the use case. Both possibilities exist for a reason: if Z can be a matrix but just happens to have one column, make it a column vector. If Z is always a single vector, make it 1-d unless some operation (or library) requires the other format; 1-d is usually a bit easier to work with.
In numpy, is it recommended to create column arrays (2d arrays) rather than 1d arrays? For example, whereas Z = np.zeros((12,)) defines a 1-dimensional list, it might also be preferable to form Z = np.zeros((12,1)).