Summing positive elements of each row of an array in Python

Question

I have an array A. I want to sum all the positive elements of each row of A. I present the current and expected output.

import numpy as np A=np.array([[0,-2,3],[1,0,6],[7,8,0]]) B1=[] for i in range(0,len(A)): B=np.sum(A[i]>0) B1.append(B) print(B1)

The current output is

[1, 2, 2]

The expected output is

[3,7,15]

This question is similar to: Sum of negative elements in each column of a NumPy array. If you believe it’s different, please edit the question, make it clear how it’s different and/or how the answers on that question are not helpful for your problem. — xskxzr
– xskxzr, Commented Sep 11, 2024 at 9:56

mozway · Accepted Answer · 2023-03-06 09:09:19Z

3

Use numpy.where to mask the negative values:

np.where(A>0, A, 0).sum(axis=1)

Or the where parameter of numpy.sum:

np.sum(A, axis=1, where=A>0)

Output: array([ 3, 7, 15])

answered Mar 6, 2023 at 9:02

267k13 gold badges56 silver badges106 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

The where parameter version needs an out parameter as well.