Python Numpy 'Invert' Boolean Mask Operation

When I have an array a and a boolean mask b, I can find the ‘masked’ vector c.

a = np.array([1, 2, 4, 7, 9])
b = np.array([True, False, True, True, False])

c = a[b]

Now suppose, it’s the other way around. I have c and b and would like to arrive at d (below). What is the easiest way to do this?

c = np.array([1, 4, 7])
b = np.array([True, False, True, True, False])

d = np.array([1, 0, 4, 7, 0])

>Solution :

You could use:

d = np.zeros_like(b, dtype=c.dtype)
d[b] = c

Output: array([1, 0, 4, 7, 0])