Test whether each element of a 1D array is also present in a second array.
Returns a boolean array the same length as ar1 that is True where an element of ar1 is in ar2 and False otherwise.
Parameters :  ar1 : array_like, shape (M,)
ar2 : array_like
assume_unique : bool, optional


Returns :  mask : ndarray of bools, shape(M,)

See also
Notes
in1d can be considered as an elementwise function version of the python keyword in, for 1D sequences. in1d(a, b) is roughly equivalent to np.array([item in b for item in a]).
New in version 1.4.0.
Examples
>>> test = np.array([0, 1, 2, 5, 0])
>>> states = [0, 2]
>>> mask = np.in1d(test, states)
>>> mask
array([ True, False, True, False, True], dtype=bool)
>>> test[mask]
array([0, 2, 0])