Molecular n-grams are generated from SMILES using the RDKit library. Given a radius r, we iterate over the heavy atoms in an input molecule and extract sub-SMILES centred on each atom with radii 0 to r, where a radius of 0 is the single central atom. In addition, rings from the SSSR (smallest set of smallest rings) are extracted as well. Compared to the atom pair-based approach by Schneider et al. , the n-grams-based fingerprint also captures stereochemistry.