hellow

i wrote an abaqus script to rad stress of elements of ODB file. my ODB has only one instances. the code is 

Delstress=rollingOdb.steps[rollingStep].frames[100].fieldOutputs['S'].values[150].data

this worked well. now i have another ODB file which has several instances. i want to get stress of elements only in one instances. but if i write above command, it is not clear in which instances, it reads stress.

can anybody tell how to include instances name to above code, OR is there separate approach to do this.