TypeError: cannot unpack non-iterable NoneType object

Question

I know this question has been asked before but I can't seem to get mine to work.

import numpy as np   def load_dataset():     def download(filename, source="http://yaan.lecun.com/exdb/mnist/"):         print ("Downloading ",filename)         import urllib         urllib.urlretrieve(source+filename,filename)      import gzip          def load_mnist_images(filename):         if not os.path.exists(filename):             download(filename)         with gzip.open(filename,"rb") as f:             data=np.frombuffer(f.read(), np.uint8, offset=16)                          data = data.reshape(-1,1,28,28)                          return data/np.float32(256)          def load_mnist_labels(filename):             if not os.path.exists(filename):                 download(filename)             with gzip.open(filename,"rb") as f:                 data = np.frombuffer(f.read(), np.uint8, offset=8)             return data          X_train = load_mnist_images("train-images-idx3-ubyte.gz")         y_train = load_mnist_labels("train-labels-idx1-ubyte.gz")         X_test = load_mnist_images("t10k-images-idx3-ubyte.gz")         y_test = load_mnist_labels("t10k-labels-idx1-ubyte.gz")          return X_train, y_train, X_test, y_test   X_train, y_train, X_test, y_test = load_dataset()   import matplotlib matplotlib.use("TkAgg")  import matplotlib.pyplot as plt plt.show(plt.imshow(X_train[3][0])) 

This is the error I am getting:

Traceback (most recent call last):   File "C:\Users\nehad\Desktop\Neha\Non-School\Python\Handwritten Digits  Recognition.py", line 38, in <module>     X_train, y_train, X_test, y_test = load_dataset() TypeError: cannot unpack non-iterable NoneType object 

I am new to machine learning. Did I just miss something simple? I am trying a Handwritten Digit Recognition project for my school Science Exhibition.

Answer 1

You get this error when you perform a multiple assignment to None (which is of NoneType). For instance:

X_train, y_train, X_test, y_test = None 

TypeError: cannot unpack non-iterable NoneType object

So if you get this, the error is most likely that the right-hand part of the assignment is not what you expected (it's nothing).