The aromatic property of all atoms and bonds in a molecule, can conveniently be reset by calling the OEChem function OEClearAromaticFlags. This is useful, for example, for writing the Kekulé form of a SMILES string, by calling OEClearAromaticFlags before calling OECreateAbsSmiString.
The OEClearAromaticFlags function is equivalent to the following code.
def MyClearAromaticFlags(mol):
for atom in mol.GetAtoms():
atom.SetAromatic(0)
for bond in mol.GetBonds():
bond.SetAromatic(0)