TypeError: cannot unpack non-iterable NoneType object

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=""): 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.

5 Answers

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).

I think your X_train, y_train, X_test, y_test are defined inside your load_mnist_imagesfunction, and are thus not defined for your load_dataset function.

You should de-indent your 5 lines from X_train = ... to return X_train, ... and your code might work better then.

Splitting/breaking multiple assignment to None resolves this issue.

e.g. This DOESN'T work:

test_set_raw, test_set_transformed, train_set_raw, train_set_transformed = None 

This DOES work (no error):

test_set_raw = None test_set_transformed = None train_set_raw = None train_set_transformed = None 

You get that error because load_dataset() returns None.

run this and you get the same error:

X_train, y_train, X_test, y_test = None 

In your code: plt.show(plt.imshow(X_train[3][0])) Add: coma before the last closing bracket, this error is showing because you're using a tuple and tuple receive coma after the last element or item in it. Do this: plt.show(plt.imshow(X_train[3][0]),)