How to use the function numpy.append

Question

I have a problem using the function numpy.append. I wrote the following function as part of a larger piece of code, however, my error is reproduced in the folowing:

Answer 1

Unlike the list append method, numpy's append does not append in-place. It returns a new array with the extra elements appended. So you'd need to do r = np.append(r, float(line[index])).

Building up numpy arrays in this way is inefficient, though. It's better to just build your list as a Python list and then make a numpy array at the end.