Gary Thompson wrote: > Rasmus Fogh wrote: >> Dear Gary, >> >> Isotope Codes are strings, like '13C', '1H', etc. Isotopes are objects, >> living in the molecule... > Hi Rasmus > > many thanks that makes everything clear ;-) > > regards > gary nb so this is what I cam up with for getIsotope: # todo add a default chemElementStore key e.g. ccpn? def getIsotope(project,symbol,massNumber): result = None chem_element = None chem_element = project.chemElementStores[0].findFirstChemElement(symbol=symbol) if chem_element: result = chem_element.findFirstIsotope(massNumber = massNumber) return result is this the best way to do it? regards gary -- ------------------------------------------------------------------- Dr Gary Thompson Astbury Centre for Structural Molecular Biology, University of Leeds, Astbury Building, Leeds, LS2 9JT, West-Yorkshire, UK Tel. +44-113-3433024 email: [log in to unmask] Fax +44-113-2331407 -------------------------------------------------------------------