numpy array , TypeError: cannot unpack non-iterable numpy.int64 object

Question

I'm going to find the max value of each column and its index in a 2D numpy ndarray but I got the error

TypeError: cannot unpack non-iterable numpy.int64 object

here is my code

import numpy as np

a = np.array([[1,0,4,5,8,12,8],
              [1,3,0,4,9,1,0],
              [1,5,8,5,9,7,13],
              [1,6,2,2,9,5,0],
              [3,5,5,5,9,4,13],
              [1,5,4,5,9,4,13],
              [4,5,4,4,9,7,4]
             ])
x,y = np.argmax(a) 
#x should be max of each column and y the index of it

does anybody know about it?

caring-goat-913 · Accepted Answer · 2020-06-29 22:03:43Z

3

np.argmax as you have it is flattening the array and returning a scalar, hence your unpacking error.

Try:

ncols = a.shape[1]
idx = np.argmax(a, axis=0)
vals = a[idx, np.arange(ncols)]

Output:

>>> idx
array([6, 3, 2, 0, 1, 0, 2])

>>> vals
array([ 4,  6,  8,  5,  9, 12, 13])

answered Jun 29, 2020 at 22:03

caring-goat-913

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Ehsan · Accepted Answer · 2020-06-29 22:04:46Z

2

You need this:

x = a.max(0)
y = a.argmax(0)

answered Jun 29, 2020 at 22:04

Ehsan

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