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How find values in an array that meet two conditions using Python

I have an array

a=[1,2,3,4,5,6,7,8,9]

and I want to find the indices of the element s that meet two conditions i.e.

a>3 and a<8
ans=[3,4,5,6]
a开发者_JAVA技巧[ans]=[4,5,6,7]

I can use numpy.nonzero(a>3) or numpy.nonzero(a<8) but not numpy.nonzero(a>3 and a<8) which gives the error:

ValueError: The truth value of an array with more than one element is
ambiguous. Use a.any() or a.all()

When I try to use any or all I get the same error. Is it possible to combine two conditional tests to get the ans?


numpy.nonzero((a > 3) & (a < 8))

& does an element-wise boolean and.


An alternative (which I ended up using) is numpy.logical_and:

choice = numpy.logical_and(np.greater(a, 3), np.less(a, 8))
numpy.extract(choice, a)


if you use numpy array, you can directly use '&' instead of 'and'.

a=array([1,2,3,4,5,6,7,8,9])
a[(a>3) & (a<8)]
ans=array([3,4,5,6])


Side note, this format works for any bitwise operation.

numpy.nonzero((a > 3) | (a < 8)) #[or]
numpy.nonzero((a > 3) & (a < 8)) #[and]
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