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Accessing a value in a 2D arrayAccessing columns of a 2D arrayAccessing rows of a 2D arrayCalculating the determinant of a matrixChecking allowed values for a NumPy data typeChecking if a NumPy array is a view or copyChecking the version of NumPyChecking whether a NumPy array contains a given rowComputing Euclidean distance using NumpyConcatenating 1D arraysConverting array to lowercaseConverting type of NumPy array to stringCreating a copy of an arrayDifference between Python List and Numpy arrayDifference between the methods array_equal and array_equivDifference between the methods mod and fmodDifference between the methods power and float_powerFinding the closest value in an arrayFinding the Index of Largest Value in a Numpy ArrayFinding the Index of Smallest Value in a Numpy ArrayFinding the most frequent value in a NumPy arrayFlattening Numpy arraysGetting constant PiGetting elements from a two dimensional array using two dimensional array of indicesGetting indices of N maximum valuesGetting indices of N minimum valuesGetting the number of columns of a 2D arrayGetting the number of non-zero elements in a NumPy arrayGetting the number of rows of a 2D arrayInitializing an array of onesInitializing an array of zerosInitializing an identity matrixLimiting array values to a certain rangePerforming linear regressionPrinting full or truncated NumPy arrayPrinting large Numpy arrays without truncationRemoving rows containing NaN in a NumPy arrayReversing a NumPy arraySaving NumPy array to a fileShape of Numpy ArraysSorting value of one array according to anotherSuppressing scientific notation
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Getting the number of non-zero elements in a NumPy array

NumPy
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schedule Jul 1, 2022
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To get the number of non-zero elements in a NumPy array use the count_nonzero(~) method.

Examples

1D array

To count the number of non-zero elements in a 1D array:

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

2D array

To count the number of non-zero elements in a 2D array:

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

To count the number of non-zero elements row-wise:

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

To count the number of non-zero elements column-wise:

np.count_nonzero([[1,0,1],[0,1,0]], axis=0)
array([1, 1, 1])
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Published by Arthur Yanagisawa
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