Hi This questions might seem stupid, but I didn't get a clever solution myself, or found one in the archives, the cookbook, etc. . If I overlooked something, please give a pointer. Well, if I have an 1D array like [ 0. , 0.1, 0.2, 0.3, 0.4, 0.5] ,a scalar like 0.122 and want to retrieve the index postion of the closest value of the scalar in the array: Is there any fast method to get this? Right now I've implemented the following method: def _get_value_index(value, a): mindiff = 1e20 index = 0 for intensity, temp_index in zip(a, xrange(a.shape[0])): diff = abs(intensity - value) #closer to given value? if diff <= mindiff: mindiff = diff index = temp_index return index It works, but is akward and takes too much time (I've no benchmark), if the array is long and the method called often within a different function. But it should help clarify the problem. TIA Christian