Tanimoto Similarity is low between the original SMILES and the standardized.

[mainguyenanhvu]

I use your example to calculate Tanimoto Similarity (using RDKIT), and it returns the low score (0.5917602996254682).
These SMILES: [Na]OC(=O)c1ccc(CS+2([O-]))cc1, [Na+].O=C([O-])c1ccc(CS(=O)=O)cc1.

My code:

    mol1 = RDKitChem.MolFromSmiles(smiles1)
    mol2 = RDKitChem.MolFromSmiles(smiles2)

    if mol1 is None or mol2 is None:
        return 0.0

    fp1 = RDKitChem.RDKFingerprint(mol1)
    fp2 = RDKitChem.RDKFingerprint(mol2)

    return RDKitChem.DataStructs.TanimotoSimilarity(fp1, fp2)

I am newbie to cheminfo. Please explain it. Thank you very much.