How does python numpy.where() work?

Question

I am playing with numpy and digging through documentation and I have come across some magic. Namely, I am talking about numpy.where():

>>> x = np.arange(9.).reshape(3, 3) 

>>> np.where( x > 5 ) 

(array([2, 2, 2]), array([0, 1, 2]))

How do they achieve internally that you are able to pass something like x > 5 into a method? I guess it has something to do with __gt__ but I am looking for a detailed explanation.

Answer 1

The python numpy.where() works as follows:-

Any sort of logical operation on a numpy array returns a boolean array. (i.e. __gt__, __lt__, etc all return boolean arrays where the given condition is true).

Example:-

x = np.arange(9).reshape(3,3)

print x > 5

To know more about this you can have a look at the following video tutorial:-