3D metrics for segmentation evaluation
Realy, dud its childish!

only ones:

lenf = len(folder)


just one 2d array:

len_types = 12
arr = np.zeros([lenf ,  12])


learn how to work with numpy arrays, you will avoid the loop as well. And for example the mean can be done in one line for 2d array:

means = np.mean(arr, axis = 1)


https://docs.scipy.org/doc/numpy/reference/generated/numpy.mean.html