How to index residues by icode in biopython?
Okay, I found the answer myself. It is possible to index not only by RES_NUM, but by its id (check with residue.get_id()), so the below example would work:
#structure[0][RES_CHAIN][het, resseq, icode]
structure[0][RES_CHAIN][' ', 27, 'A']