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pickle.load: need more than 2 values to unpack
I have finished writing a .pkl file but error appears when I try to load it.
            f = open('train.pkl')
            X, Y, X_test, Y_test = cPickle.load(f)

or
            X, Y ,X_test,Y_test=pickle.load(open("train.pkl","rb"))

Both attempts failed. The code for writing the .pkl file is as below.
Inside the loop to process the images and labels:
            img_ndarray = numpy.asarray(img, dtype='float64')
            img_raw[i] = numpy.ndarray.flatten(img_ndarray)
            img_label[i]=numpy.asarray(name,dtype='float64')
            i=i+1

Outside the loop to write the pickle file:
            write_file = open('train.pkl', 'wb')
            cPickle.dump([[img_raw[0:4],img_label[0:4]], [img_raw[5:7], img_label[5:7]]],write_file, -1)
            write_file.close()

Thank you for any input.

The error message should make this obvious, you've pickled a list with 2 elements, so you can't unpack that into 4 names. Consider (making up some data):
In [35]: img_raw, img_label = range(10), 'abcdefghhijlmnop'

In [36]: [[img_raw[0:4],img_label[0:4]], [img_raw[5:7], img_label[5:7]]]
Out[36]: [[range(0, 4), 'abcd'], [range(5, 7), 'fg']]

In [37]: len([[img_raw[0:4],img_label[0:4]], [img_raw[5:7], img_label[5:7]]])
Out[37]: 2

However, this is easily remedied, since each of the sublists has 2 items in them too:
In [38]:  (X, Y) , (X_test, Y_test) = [[img_raw[0:4],img_label[0:4]], [img_raw[5:7], img_label[5:7]]]

And it works!
In [41]: X
Out[41]: range(0, 4)

In [42]: Y
Out[42]: 'abcd'

In [43]: X_test
Out[43]: range(5, 7)

In [44]: Y_test
Out[44]: 'fg'

In general, what you unpack into has to have the same shape:
In [45]: data = [[[1, 2], [3, 4, 5]],[6, [7, 8]]]

In [46]: (((a, b), (c, d, e)), (f, (g, h))) = data

In [47]: a,b,c,d,e,f,g,h
Out[47]: (1, 2, 3, 4, 5, 6, 7, 8)

