import mxnet as mx import numpy as np a1 = np.random.randint(0, 256, (8, 8, 3)) a2 = np.random.randint(0, 256, (8, 8, 3)) a3 = np.random.randint(0, 256, (8, 8, 3)) a4 = mx.nd.array(a1) a5 = mx.nd.array(a2) a6 = mx.nd.array(a3) np_img = [a1, a2, a3] mx_img = [a4, a5, a6] #OK img_array = mx.nd.array(np_img).astype('uint8') #not OK #img_mxarray = mx.nd.array(mx_img) #Alternative1 import gluoncv img_mxarray1 = gluoncv.data.batchify.Stack()(mx_img) #Alternative2 img_mxarray2 = mx.nd.concat(*[x.expand_dims(0) for x in mx_img], dim=0)