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:UsersnehadDesktopNehaNon-SchoolPythonHandwritten 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.

Asked By: Neha Devi Shakya

||

Source

Answer 1

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.

Answered By: Amaras

Answer 2

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

Answered By: EyaS

Answer 3

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).

Answered By: Nicolas Gervais

Answer 4

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

Answered By: diman82

Answer 5

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]),)

Answered By: Gabriel J

TypeError: cannot unpack non-iterable NoneType object

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