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Parameters Return value Examples Basic usage Counting non-zeros row-wise Counting non-zeros column-wise

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NumPy | count_nonzero method

schedule Aug 10, 2023

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Parameters Return value Examples Basic usage Counting non-zeros row-wise Counting non-zeros column-wise

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Numpy's count_nonzero(~) method counts the number of non-zeros in an array along a given axis.

Parameters

1. a | array-like

The array on which to perform the method.

2. axislink | int or tuple<int> | optional

The axis along which we count the number of non-zeros. By default, axis=None.

Return value

An int or Numpy array indicating the number of non-zeros in the input array along the given axis.

Examples

Basic usage


        
        
            
                
                
                    np.count_nonzero([1,0,2,0,3])
                
            
            3

Counting non-zeros row-wise

To count the number of non-zeros row-wise in a 2D Numpy array, use the following:


        
        
            
                
                
                    np.count_nonzero([[1,0,1],[0,1,0]], axis=1)
                
            
            array([2, 1])

We get this result because we have 2 non-zeros in the first row, and 1 non-zero in the second row.

Counting non-zeros column-wise

To count the number of non-zeros column-wise in a 2D Numpy array, use the following:


        
        
            
                
                
                    np.count_nonzero([[1,0,1],[0,1,0]], axis=0)
                
            
            array([1, 1, 1])

We get this result because every column contains exactly 1 non-zero value.

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Published by Isshin Inada

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