I have a numpy array with positive and negative values in. a = array([1,1,-1,-2,-3,4,5]) I want to create another array which contains a value at each index where a sign change occurs (For example, if the current element is positive and the previous element is negative and vice versa). For the array above, I would expect to get the following result array([0,0,1,0,0,1,0]) Alternatively, a list of the positions in the array where the sign changes occur or list of booleans instead of 0's and 1's is fine.