datum = caffe.proto.caffe_pb2.Datum()
datum.channels = X.shape[1]
datum.height = X.shape[2]
datum.width = X.shape[3]
datum.data = X[i].tostring() # or .tobytes() if numpy < 1.9
datum.label = int(y[i])
str_id = '{:08}'.format(i)
# The encode is only essential in Python 3
txn.put(str_id.encode('ascii'), datum.SerializeToString())
