I tried both get_data and get_timeseries to fetch history of cash basis data(which works with the EXCEL API) but returns only NaNs when called via python.

May be I do not know the correct field via eikon python api, but different options available under "Data Item Browser" is not fetching the data.

tmpdf,err=ek.get_data('CORNMQEHNP-Z', ['TR.MIDPRICE.date','TR.MIDPRICE'], parameters={'SDate':'20170906','EDate':'20181001'})
ethanol_spot = ek.get_timeseries('CORNMQEHNP-Z', start_date=datetime.datetime(2016, 1, 1), end_date=datetime.datetime(2018, 12, 31), interval='daily', fields=['LAST_QUOTE.Close'])