(Python) Find the indices of the values in two arrays that are equal to the values in two other arrays

I have the following 4 arrays and I want to get the indices of the values that are equal in the arrays A and X corresponding to the values in the same position in B and Y. So for the following example,

    import numpy as np
    A = np.asarray([400.5, 100,  700,   200,  15, 900])
    B = np.asarray([500.5, 200,  500, 600.5,   8, 999])
    X = np.asarray([400.5, 700,  100,   300,  15, 555, 900])
    Y = np.asarray([500.5, 500,600.5,   100,   8, 555, 999])

I want to get two arrays with the indices:

indAB = [0 2 4 5]

• 0 because 400.5 and 500.5 in A&B are also in X&Y in the position 0
• 2 because 700 and 500 in A&B are also in X&Y in the position 2
• 4 because 15 and 8 in A&B are also in X&Y in the position 4
• 5 because 900 and 999 in A&B are also in X&Y in the position 5

indXY = [0 1 4 6]

• 0, 1, 4, and 6 are found similar to indAB but with respect to X&Y instead.

where indAB are the indices of the values in A and B that are equal to the values in X and Y and indXY are the indices of the values in X and Y that are equal to the values in A and B.

This is my attempt so far:

    def indices(a,b):
        setb = set(b)
        ind = [i for i, x in enumerate(a) if x in setb]
        return ind

    iA = np.asarray(indices(A,X))
    iB = np.asarray(indices(X,A))
    iX = np.asarray(indices(B,Y))
    iY = np.asarray(indices(Y,B))

    def CommonIndices(a,b):
        return np.asarray(list(set(a) & set(b)))

    indAB = CommonIndices(iA,iX)
    indXY = CommonIndices(iB,iY)

    print(indAB) # returns = [0 2 4 5]
    print(indXY) # returns = [0 1 2 4 6]

I keep getting [0 1 2 4 6] for indXY which is incorrect. 2 is not supposed to be included because even though 600.5 is in Y and B, 200 and 100 in A and B (respectively) are not equal.

I would be very grateful if someone could offer a solution to this. Many thanks!