Hello, Consider my masked arrays: I[28]: type basic.data['Air_Temp'] -----> type(basic.data['Air_Temp']) O[28]: numpy.ma.core.MaskedArray I[29]: basic.data['Air_Temp'] O[29]: masked_array(data = [-- -- -- ..., -- -- --], mask = [ True True True ..., True True True], fill_value = 999999.9999) I[17]: basic.data['Air_Temp'].data = np.ones(len(basic.data['Air_Temp']))*30 --------------------------------------------------------------------------- AttributeError Traceback (most recent call last) ----> 1 2 3 4 5 AttributeError: can't set attribute Why this assignment fails? I want to set each element in the original basic.data['Air_Temp'].data to another value. (Because the main instrument was forgotten to turn on for that day, and I am using a secondary measurement data for Air Temperature for my another calculation. However it fails. Although single assignment works: I[13]: basic.data['Air_Temp'].data[0] = 30 Shouldn't this be working like the regular NumPy arrays do? Thanks. -- Gökhan