python - 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 step please?

>>> np.where([[True, False], [True, True]],
...          [[1, 2], [3, 4]],
...          [[9, 8], [7, 6]])
array([[1, 8],
       [3, 4]])

Answer 1

The basic syntax is np.where(x, a, b) Wherever x is true, take that element of a, and wherever it's false, take an element of b. It's equivalent to something like this:

x = . . [[1, 0], [1, 1]]), not x =[[0, 1], [0, 0 ]]

array([[1, 2], [3, 4]]) + array([[7, 8], [9, 10]])

array([[1, 0], [3, 4]]) + array([[0, 8], [0, 0 ]]) = array([[1, 8], [3, 4]])