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pythonarraysnumpysum

Summing each array inside list

I have a list of arrays generated from another function:

testGroup = [array([18]), array([], dtype=int64), array([56, 75, 55, 55]), array([32])]

I'd like to return the sum of each individual array in the list, with the empty ones returning as zero

I've tried using numpy, as per the documentation:

np.sum([[0, 1], [0, 5]], axis=1)
array([1, 5])np.sum([[0, 1], [0, 5]], axis=1)
array([1, 5])

But when I try np.sum(testGroup, axis=1) I get an axis error as I suppose the empty arrays have a dimension less than one?

I've also tried summing it directly arraySum = sum(testGroup) but get a ValueError

Any ideas on how to achieve a sum of the arrays inside the testGroup list?

Solution

  • testGroup is a plain python list, that happens to contain numpy.array elements. Instead you can use a list comprehension

    >>> [np.sum(a) for a in testGroup]
[18, 0, 241, 32]