Numpy where syntax from docs

Question

Trying to teach myself some python and I am super confused from the docs what the where function does. Can somebody explain the example from the documentation below step by

Answer 1

I think it becomes pretty clear when you add linebreaks to arrange the inputs to look like matrices:

np.where( # First argument
         [[True, False], 
          [True, True]],
          # Second argument
          [[1, 2], 
           [3, 4]],
          # Third argument
          [[9, 8], 
           [7, 6]])

You can see the first argument as a mask that determines from which of the two following inputs elements should be taken.

The result

array([[1, 8],
       [3, 4]])

contains elements from the second argument wherever the mask is True and elements from the third argument where it is False.